Search found 109 matches

by Ashley Ko 3I
Sat Mar 06, 2021 2:01 pm
Forum: General Rate Laws
Topic: Increasing or decreasing the rate constant
Replies: 1
Views: 17

Increasing or decreasing the rate constant

Does adding a catalyst increase or decrease the rate constant? Does increasing the temperature always increase the rate constant? Why does temperature and catalysts increase/decrease the rate constant?
by Ashley Ko 3I
Sat Mar 06, 2021 1:06 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Molecularity
Replies: 10
Views: 26

Molecularity

When determining the molecularity of an elementary step, can we look at stoichiometric coefficients? For example, if the reactants are 2A + B, would the molecularity be trimolecular? Thank you in advance!
by Ashley Ko 3I
Sat Mar 06, 2021 12:52 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Pseudo rate constant and rate constant
Replies: 2
Views: 21

Pseudo rate constant and rate constant

Hi! In Friday's lecture, Professor Lavelle mentioned the following equation: k = k'/([B0]^M*[C0]^L). What are the values of M and L? Do we assume we already obtained those values from experiments?
by Ashley Ko 3I
Tue Mar 02, 2021 9:56 pm
Forum: Balancing Redox Reactions
Topic: 6K3d
Replies: 1
Views: 13

Re: 6K3d

Hi! The chemical equation given in the textbook is wrong. The chemical equation should be the following: Cl2(g) ---> ClOH(aq) + Cl-(aq) (see Professor Lavelle's solution manual errors on his class website). Hope this helps!
by Ashley Ko 3I
Tue Mar 02, 2021 9:48 pm
Forum: Balancing Redox Reactions
Topic: 6k.3 d) Identifying Half Reactions
Replies: 4
Views: 27

Re: 6k.3 d) Identifying Half Reactions

Hi! The chemical equation in the textbook is wrong (see Professor Lavelle's solution manual errors on his class website). The chemical equation should be the following: Cl2(g) --> ClOH(aq) + Cl-(aq). In this case, Cl is being reduced and oxidized (Cl2 is both the reducing and oxidizing agent). Hope ...
by Ashley Ko 3I
Sat Feb 27, 2021 11:47 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: delta G knot equation confusion
Replies: 2
Views: 21

Re: delta G knot equation confusion

Hi! To find the number of moles of electrons transferred (or the number of electrons transferred), I think it is helpful to write the half-reactions and then balance them. If the number of electrons in each half-reaction is different, you have to multiply the half-reactions by some constant so that ...
by Ashley Ko 3I
Sat Feb 27, 2021 3:54 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Sapling Week 7/8 #9 Set Up
Replies: 1
Views: 15

Re: Sapling Week 7/8 #9 Set Up

Hi! Your steps seem correct. Maybe check that you are using the correct value for Fe? There are multiple reduction half-reactions listed with Fe in it. Make sure to use the standard potential value corresponding with the following reduction half-reaction for Fe: Fe^2+(aq) + 2e- ---> Fe(s). Another m...
by Ashley Ko 3I
Sat Feb 27, 2021 3:39 am
Forum: Balancing Redox Reactions
Topic: Sapling Week 7/8 #5
Replies: 3
Views: 42

Re: Sapling Week 7/8 #5

Update: I figured out what I was doing wrong but if anyone has any tips for balancing redox reactions, I would greatly appreciate it!
by Ashley Ko 3I
Sat Feb 27, 2021 3:35 am
Forum: Balancing Redox Reactions
Topic: Sapling #5
Replies: 6
Views: 43

Re: Sapling #5

Hi! I got the same answer as you. Maybe check how you entered the chemical equation into Sapling? You have to use the various tools they give you. For example, for exponents and subscripts make sure to use the tools with an X and a box (the box is either in the exponent or subscript position). Also,...
by Ashley Ko 3I
Sat Feb 27, 2021 3:22 am
Forum: Balancing Redox Reactions
Topic: Sapling #5
Replies: 6
Views: 43

Re: Sapling #5

Hi! Could you post the original question? I had different chemical equations.
by Ashley Ko 3I
Sat Feb 27, 2021 12:56 am
Forum: Balancing Redox Reactions
Topic: Sapling Week 7/8 #5
Replies: 3
Views: 42

Sapling Week 7/8 #5

Hi everyone!

Can someone help explain how to balance the equation for N2H4 + ClO3^- --> NO + Cl^-? I have tried several times but keep on getting the wrong answer. Thank you for everyone's responses in advance!
by Ashley Ko 3I
Wed Feb 17, 2021 10:56 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Larger mass= higher molar entropy
Replies: 4
Views: 15

Re: Larger mass= higher molar entropy

Hi! I believe a greater mass results in a higher molar entropy because of the following: a greater mass means a greater number of subatomic particles, which means a greater number of microstates since each subatomic particle can occupy different positions. A greater number of microstates means a gre...
by Ashley Ko 3I
Wed Feb 17, 2021 10:32 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Entropy of Helium vs. Ethanol
Replies: 1
Views: 11

Re: Entropy of Helium vs. Ethanol

Hi! I believe there are two types of entropy: residual entropy (positional entropy) and thermal entropy. When determining which compound has the greater entropy, the phase of the compounds is more important than the complexity of the compounds. For instance, gases will always have greater entropy th...
by Ashley Ko 3I
Wed Feb 17, 2021 10:14 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Phase Change
Replies: 3
Views: 27

Re: Phase Change

Hi! I'm not completely sure since I am confused about the exact situations surrounding equilibrium myself but maybe someone else could confirm the following: A phase change indicates equilibrium between two phases. I believe that although we can assume that delta G is equal to 0 during a phase chang...
by Ashley Ko 3I
Mon Feb 15, 2021 11:25 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneity
Replies: 5
Views: 32

Re: Spontaneity

Hi! The reason a positive entropy change means a spontaneous reaction is because an increase in entropy means a decrease in the Gibbs free energy as seen in the following equation: delta G = delta H - T*delta S. I believe a negative delta G (regardless if it is standard Gibbs free energy or not) ind...
by Ashley Ko 3I
Mon Feb 15, 2021 11:13 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Internal Energy of a Closed System
Replies: 5
Views: 36

Re: Internal Energy of a Closed System

Hi! Hopefully, the following can answer a few of your questions . . . - The internal energy of a closed system can be changed in two ways: heating/cooling and compression/expansion. - The volume can be changed in closed systems; thus, the work can be calculated for closed systems if there is compres...
by Ashley Ko 3I
Sun Feb 14, 2021 12:00 pm
Forum: Calculating Work of Expansion
Topic: Expansion and equilibrium
Replies: 2
Views: 21

Expansion and equilibrium

Hi everyone! Is the end result of expansion/compression pressure equilibrium between the system and its surroundings. For example, does a system with a pressure of 2 atm keep increasing in volume until its pressure is equal to its surroundings, which has a constant pressure of 1 atm (constant extern...
by Ashley Ko 3I
Sun Feb 14, 2021 4:32 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isobaric meaning [ENDORSED]
Replies: 1
Views: 21

Isobaric meaning [ENDORSED]

Hi everyone! I am a little confused about what isobaric actually refers to. I know that isobaric means constant pressure; however, is the pressure its referring to the pressure of the system/reaction, external pressure, or both?
by Ashley Ko 3I
Sun Feb 14, 2021 4:21 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Week 5/6 Sapling #7 Conceptually
Replies: 1
Views: 13

Re: Week 5/6 Sapling #7 Conceptually

Hi! So, the heat of vaporization is typically the amount of heat it takes to vaporize one gram of a substance (units is usually in J/g for example). However, for this question, they ask for kJ/mol. Thus, you have to convert the joules to kilojoules and grams to moles in your calculation.
by Ashley Ko 3I
Sat Feb 13, 2021 7:54 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Sapling Week 5/6 #18
Replies: 7
Views: 47

Re: Sapling Week 5/6 #18

Hi! So, to isolate K, you would first divide delta G r by -RT, resulting in the following: (delta G r /(-RT)) = ln(K). Then, you would make each side the exponent of e to get rid of the natural log (e to the power of a natural log leaves you with the input(s) of the natural log for example e^(ln(2))...
by Ashley Ko 3I
Mon Feb 08, 2021 12:44 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Sapling Weeks 5 & 6 #5
Replies: 1
Views: 13

Re: Sapling Weeks 5 & 6 #5

Hi! I believe the only mistake I saw was the value you used for the gas constant. Since the units used in the equation include L, atm, and K, the gas constant value you should use is 0.0821 L*atm/(mol*K). Hope this helps!
by Ashley Ko 3I
Sun Feb 07, 2021 12:56 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Positive vs Negative Heat Capacities
Replies: 3
Views: 10

Re: Positive vs Negative Heat Capacities

Hi! I believe that heat capacity has to always be a positive value since it represents the amount of heat required (adding heat so endothermic and a positive value) to raise the temperature of the compound by 1 temperature unit (typically either K or C). The same reasoning applies to specific heat c...
by Ashley Ko 3I
Sun Feb 07, 2021 12:51 pm
Forum: Phase Changes & Related Calculations
Topic: Boiling water
Replies: 25
Views: 112

Re: Boiling water

Hi! I agree with many of the posts above! During a phase change from liquid to vapor, heat is being used to break the attractive forces/bonds between the liquid molecules (because heat is being used to break the attractive forces/bonds, the temperature doesn't change during a phase change). Water sp...
by Ashley Ko 3I
Sun Feb 07, 2021 12:42 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Sapling Question #9 Week 3/4
Replies: 3
Views: 34

Re: Sapling Question #9 Week 3/4

Hi! I believe that for this question, you would use q (heat gained) = -q (heat lost). The water with the higher temperature would represent -q (heat lost) and the water with the lower temperature would represent q (heat gained). First, you would need to convert the volumes to mass using the density ...
by Ashley Ko 3I
Sun Feb 07, 2021 3:44 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Homework Problem 4C.13
Replies: 2
Views: 11

Re: Homework Problem 4C.13

Hi! I believe that for this question, you would essentially use the following equation: q (heat gained) = -q (heat lost). However, you would also need to add the amount of heat it takes for the phase change from solid (ice cube) to liquid (water) to the q (heat gained) side. So, the overall equation...
by Ashley Ko 3I
Sat Feb 06, 2021 7:28 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: week 5/6 sapling #14
Replies: 1
Views: 27

Re: week 5/6 sapling #14

Hi! For this question you use the following equation: delta G = delta H - T*delta S. You first set delta G equal to 0 because at boiling point the compound is at equilibrium, specifically between the liquid and vapor phase. Then, you solve for T by substituting delta G and the values given in the qu...
by Ashley Ko 3I
Sat Feb 06, 2021 5:30 pm
Forum: Ideal Gases
Topic: Ideal Gas
Replies: 3
Views: 33

Re: Ideal Gas

Hi! I believe an ideal gas is a gas whose molecules are not attracted to one another (no intermolecular forces between molecules) and any collisions between the molecules are completely elastic, meaning no energy is lost. Gases under STP conditions tend to be referred to as ideal gases (STP means &q...
by Ashley Ko 3I
Sun Jan 31, 2021 6:20 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Sapling WEEK 3/4 Q #5
Replies: 4
Views: 23

Re: Sapling WEEK 3/4 Q #5

Hi! For this question, you would use Hess's law and manipulate the chemical equations in order to get 2M + 3Cl2 = 2MCl3. As for manipulating the chemical equations, you want to try to manipulate them in a way such that when you combine the chemical equations together you get 2M + 3Cl2 = 2MCl3 (if tw...
by Ashley Ko 3I
Sun Jan 31, 2021 3:37 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Neutralization
Replies: 25
Views: 105

Re: Neutralization

Does this mean that the salt and the water are both neutral solutions (pH=7)? I don't think this is necessarily true since the salt can be acidic, basic, or neutral depending on its ions or, in other words, the strength of the acid and base that formed the salt. For instance, a neutralization react...
by Ashley Ko 3I
Sun Jan 31, 2021 3:30 pm
Forum: Phase Changes & Related Calculations
Topic: Sapling Week 3/4 Q10
Replies: 3
Views: 32

Re: Sapling Week 3/4 Q10

Hi! I believe for this question you would just use q (heat gained) = -q (heat lost) except add the q or heat it takes for the phase change from solid (ice cube) to liquid on the q side. In other words, you would use q (heat for phase change) + q (heat gained) = -q (heat lost). For the phase change, ...
by Ashley Ko 3I
Sun Jan 31, 2021 5:10 am
Forum: Phase Changes & Related Calculations
Topic: Sarah Tang Workshop Question
Replies: 2
Views: 48

Re: Sarah Tang Workshop Question

Hi! This question involves several heat calculations. The first calculation involves using q = m*C*delta T to calculate how much heat it takes to increase the temperature of the ice cube from -10 degrees celsius to 0 degrees celsius (melting point of water). The second calculation involves using q =...
by Ashley Ko 3I
Sun Jan 31, 2021 4:34 am
Forum: Calculating Work of Expansion
Topic: Energy and the System/Surroundings
Replies: 8
Views: 35

Re: Energy and the System/Surroundings

Hi! I agree with the above post! Energy can be transferred between a system and its surroundings if, for example, heat is absorbed or lost by a system. A real-life example would be a cooling pack. The cooling pack (the system) feels cold because it is absorbing heat from its surroundings (your hand)...
by Ashley Ko 3I
Sun Jan 31, 2021 4:19 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Sapling HW Week 3/4 #9
Replies: 2
Views: 26

Re: Sapling HW Week 3/4 #9

Hi! For this question, you first need to convert the volume of the water to mass (this step is simple since the volume to mass ratio of water is 1:1). Then, you would use the equation q (heat gained) = -q (heat lost), where q = m*C*delta T. In this case, q (heat gained) would represent the heat ener...
by Ashley Ko 3I
Sun Jan 24, 2021 12:46 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5% rule for checking the validity of assumptions
Replies: 10
Views: 66

5% rule for checking the validity of assumptions

Hi everyone! I was wondering if anyone knew whether or not the 5% rule that we use to check whether or not an assumption is valid applies to partial pressures as well. For example, can we assume that x is small enough to approximate when x is less than 5% of the initial partial pressure? Or do we ju...
by Ashley Ko 3I
Sun Jan 24, 2021 12:31 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: figuring out whether salts are acidic or basic
Replies: 4
Views: 23

Re: figuring out whether salts are acidic or basic

Hi! I believe that since H3PO4 is a basic salt, this means that it tends to attract H+ ions from the water because bases tend to be proton acceptors. Also, by looking at the ions that H3PO4 dissociates into, PO4^3- is the ion that makes the salt basic (it is a basic anion) and would attract H+ proto...
by Ashley Ko 3I
Sat Jan 23, 2021 3:55 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Weak Acids
Replies: 8
Views: 63

Re: Weak Acids

Hi! I believe that for acids, it's typically acid + water yields conjugate base + hydronium ion, and for bases, it's typically base + water yields conjugate acid + hydroxide ion. Hope this helps!
by Ashley Ko 3I
Sat Jan 23, 2021 3:45 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: X Approximations
Replies: 23
Views: 108

Re: X Approximations

Hi! I believe that Professor Lavelle said that if the value of Ka/Kb is less than 10^-4, then it is safe to assume that the value of x is small enough to approximate. However, to check if your approximation is valid, divide x by the initial concentration and then multiply by 100%. If x is less than ...
by Ashley Ko 3I
Sat Jan 23, 2021 3:28 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: H3O+ and OH- concentration
Replies: 3
Views: 42

Re: H3O+ and OH- concentration

Hi! I'm not completely sure, but I think it would be safe to assume that [H3O+] = [OH-] in the absence of other information (like the presence of acids/bases or the pH or pOH) and even if the Kw is not equal to 10^-14 as a result of a change in temperature (the value of the hydronium/hydroxide conce...
by Ashley Ko 3I
Tue Jan 19, 2021 11:37 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Sapling Question 3
Replies: 4
Views: 57

Re: Sapling Question 3

Hi! By using the quadratic equation, x = -b +/- rad(b^2-4ac)/2a, you can solve for x, which represents the concentration of the ions resulting from the dissociation of the acid or base. Then, you can find the percent ionization by dividing x by the initial concentration of the acid or base (given in...
by Ashley Ko 3I
Sun Jan 17, 2021 12:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc and Kp
Replies: 11
Views: 54

Re: Kc and Kp

Hi! You use Kc or Kp mainly based on the values given in the question. For instance, Kc is used when concentrations are given and Kp is used when partial pressures are given. However, Kp only applies to gases. Kc applies to both aqueous solutions and gases. You can also convert between concentration...
by Ashley Ko 3I
Sun Jan 17, 2021 11:56 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: endothermic/exothermic Q and K
Replies: 16
Views: 95

Re: endothermic/exothermic Q and K

Hi! A negative delta H means the reaction is exothermic and heat is a product (this is because heat is released). A positive delta H means the reaction is endothermic and heat is a reactant (this is because heat is required for the reaction to proceed forward). When the temperature is increased, thi...
by Ashley Ko 3I
Sat Jan 16, 2021 10:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Box
Replies: 5
Views: 33

Re: ICE Box

Hi! I believe you use an ICE box (or RICE box) when dealing with weak acids/bases or when trying to find the equilibrium concentrations after a concentration change. "R" stands for the reaction, "I" stands for initial concentration, "C" stands for change, and "E&qu...
by Ashley Ko 3I
Sat Jan 16, 2021 4:49 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Concentration of the Reactants and Products based on the Value of K
Replies: 4
Views: 37

Concentration of the Reactants and Products based on the Value of K

Hi! I was wondering what you could tell about the concentrations of the reactants and products based on the value of K? For example, when K = 1, does that mean the concentration of the reactants = the concentration of the products? Or is this only true if both the number of reactants and products an...
by Ashley Ko 3I
Sat Jan 16, 2021 4:39 pm
Forum: Student Social/Study Group
Topic: Chemistry Community Posts
Replies: 22
Views: 70

Re: Chemistry Community Posts

I'm not completely sure, but last quarter, I believe it was 50 posts total by the end of the quarter. I would just post at least 5 times by the end of each week just to be safe (plus posting consistently helps keep you on track for 50 posts total by the end of the quarter). Hope this helps!
by Ashley Ko 3I
Fri Jan 15, 2021 11:25 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: If P doubles
Replies: 4
Views: 23

Re: If P doubles

Hi! I agree with the post above! If the pressure is doubled by halving the volume, then the concentration of the gases would increase. This can be seen through the concentration equation: concentration = n/V (n = moles of gas, V = volume). There is an inverse relationship between volume and concentr...
by Ashley Ko 3I
Fri Jan 15, 2021 11:05 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Week 2 Sapling Homework - Question #1
Replies: 3
Views: 46

Re: Week 2 Sapling Homework - Question #1

Hi! I believe you can determine the H+ concentration from Ka and then use this H+ concentration to find the pH. For instance, given that Ka = [H+][A-]/[HA], you can solve for the H+ concentration by substituting Ka and the acid concentration, which are given in the question, into the equation. Then,...
by Ashley Ko 3I
Sat Jan 09, 2021 11:01 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatlier's Principle concerning change in temperature
Replies: 2
Views: 18

Re: Le Chatlier's Principle concerning change in temperature

I believe Le Chatlier's principle does apply to temperature changes. For example, if a reaction is exothermic (heat is a product), then a temperature increase would cause the reaction to shift left. If a reaction is endothermic (heat is a reactant), then a temperature increase would cause the reacti...
by Ashley Ko 3I
Sat Jan 09, 2021 2:44 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook eq constant table 5G.2
Replies: 2
Views: 15

Re: Textbook eq constant table 5G.2

Hi! I believe K refers to equilibrium constants calculated with partial pressures while Kc refers to equilibrium constants calculated with concentrations. If all the species in a reaction are gases (since pure substances are not involved in the calculations they can be disregarded), then calculate K...
by Ashley Ko 3I
Sat Jan 09, 2021 2:32 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Calculating Q
Replies: 7
Views: 33

Re: Calculating Q

Hi! I believe you are correct. Since pure substances (solids and liquids) are not used to calculate reaction quotients/equilibrium constants, the only species left is a gas; thus, the partial pressure equilibrium constant would be calculated. Hope this helps!
by Ashley Ko 3I
Sat Jan 09, 2021 2:24 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: terminology
Replies: 11
Views: 94

Re: terminology

Hi! When a reaction favors the reactants, this means the reaction will proceed in a manner to form more reactants (in other words favoring the reverse reaction). When a reaction favors the products, this means that the reaction will proceed in a manner to form more products (in other words favoring ...
by Ashley Ko 3I
Thu Jan 07, 2021 9:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: R value
Replies: 5
Views: 72

Re: R value

Hi! I agree with the above post, but I think the first value you mentioned (0.8205...) is the one typically used since it cancels out the units in the ideal gas law equation. Hope this helps!
by Ashley Ko 3I
Thu Jan 07, 2021 9:03 pm
Forum: Administrative Questions and Class Announcements
Topic: Follow Ups
Replies: 3
Views: 46

Re: Follow Ups

Hi! I believe follow-up questions/posts to your own posts also count towards the 5 posts per week. Hope this helps!
by Ashley Ko 3I
Thu Dec 10, 2020 8:41 pm
Forum: Bronsted Acids & Bases
Topic: Net Ionic Equation for strong acid and base vs. weak acid and base
Replies: 1
Views: 10

Re: Net Ionic Equation for strong acid and base vs. weak acid and base

The HCN is not split into ions at the beginning because HCN is a weak acid (dissociation of weak acids is not significant enough). Hope this helps!
by Ashley Ko 3I
Thu Dec 10, 2020 8:32 pm
Forum: Conjugate Acids & Bases
Topic: Acids
Replies: 2
Views: 10

Re: Acids

The weaker the acid, the stronger its conjugate base is. Hope this helps!
by Ashley Ko 3I
Thu Dec 10, 2020 6:41 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate Ligands
Replies: 2
Views: 42

Re: Polydentate Ligands

Hi! I think carbonato and sulfito generally act as monodentates (in rare cases, however, they may act as bidentates). I believe the only polydentates you really need to know are oxalato (a bidentate), EDTA (a hexadentate), and en (a bidentate). Hope this helps!
by Ashley Ko 3I
Thu Dec 10, 2020 6:27 pm
Forum: Bronsted Acids & Bases
Topic: Week 10 Sapling #11
Replies: 2
Views: 16

Re: Week 10 Sapling #11

Hi! I believe in the textbook it mentions under Lewis structures how for oxoacids, meaning acids that contain O, the hydrogen bonds to the O; thus, the halogen (Cl, Br, I) would also bond to O, making O the central atom. Hope this helps!
by Ashley Ko 3I
Wed Dec 09, 2020 6:08 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Seesaw vs. trigonal pyramidal
Replies: 22
Views: 162

Re: Seesaw vs. trigonal pyramidal

No, while seesaw has 5 regions of high electron density, trigonal pyramidal only has 4 regions of high electron density. Hope this helps!
by Ashley Ko 3I
Sun Dec 06, 2020 5:28 pm
Forum: Amphoteric Compounds
Topic: Sapling HW #2 [ENDORSED]
Replies: 4
Views: 93

Re: Sapling HW #2 [ENDORSED]

Hi! A substance can act as a Bronsted acid and Bronsted base if it has BOTH of the following: a H proton that it can donate (like an acid) and a negative charge so it can accept a H proton (like a base). Hope this helps!
by Ashley Ko 3I
Sun Dec 06, 2020 3:50 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Number Question
Replies: 12
Views: 155

Re: Coordination Number Question

Hi! I agree with the above post. I also think it's important to keep in mind the denticity of the ligands in the coordination complex. For example, if one of the ligands is bidentate, then it could form 2 coordinate covalent bonds with the central atom (it would count as 2 instead of 1 towards the c...
by Ashley Ko 3I
Sun Dec 06, 2020 3:39 am
Forum: Bronsted Acids & Bases
Topic: Hydrochloric vs Hydrobromic Acid
Replies: 4
Views: 36

Re: Hydrochloric vs Hydrobromic Acid

Hi! I agree with Khoa in that HBr is a stronger acid than HCl because it is easier to remove the H proton from HBr than from HCl. I would say in terms of periodic trends, the smaller the atomic radius or the greater the electronegativity, the weaker the acid since the H proton will be harder to remo...
by Ashley Ko 3I
Sun Dec 06, 2020 3:29 am
Forum: Naming
Topic: [Co(NH3) 3Cl3]
Replies: 2
Views: 41

Re: [Co(NH3) 3Cl3]

Cobalt is 3+ because [Co(NH3)3Cl3] is neutral, NH3 is a neutral ligand, and Cl is an anionic ligand with a 1- charge (since there are three Cl, their overall charge contribution is 3-). Thus, the cobalt is 3+ so it can cancel out the charge contribution of the Cl. Hope this helps!
by Ashley Ko 3I
Wed Dec 02, 2020 2:39 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Numbers in Molecules
Replies: 3
Views: 46

Re: Coordination Numbers in Molecules

Hi! I believe that the coordination number only refers to the central atom, Fe, since Fe bonds with each CO in the coordination complex. Hope this helps!
by Ashley Ko 3I
Sun Nov 29, 2020 1:06 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Textbook #2.27
Replies: 3
Views: 10

Re: Textbook #2.27

Hi! So both CH3(-) and CH2(2-) have four regions of electron density, and since the repulsion between two lone-pairs are greater than that between two bonding atoms or a bonding atom and a lone pair, CH2(2-) would have a smaller bond angle (it has two lone pairs while CH3(-) only has one lone pair) ...
by Ashley Ko 3I
Sun Nov 29, 2020 12:51 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Polarity
Replies: 14
Views: 91

Re: Polarity

Hi! If a molecule has lone pairs, this does not always mean it is polar. For instance, a molecule with lone pairs is only polar if the lone pairs cause the atoms surrounding the central atom to become asymmetrically arranged. As a result, the dipole moments would not cancel out. However, if you are ...
by Ashley Ko 3I
Sun Nov 29, 2020 12:25 pm
Forum: Student Social/Study Group
Topic: How to study for class
Replies: 30
Views: 229

Re: How to study for class

Hi! I personally like to review by reading the textbook. I find the examples helpful and reading solidifies my understanding of the content. However, I think it’s important to also make sure to watch all the lectures at least once and complete all the homework assigned.
by Ashley Ko 3I
Sun Nov 29, 2020 12:20 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: T-Shape Polarity
Replies: 4
Views: 37

Re: T-Shape Polarity

Hi! I agree with the above post that every molecule that has a T-shape will be polar. Out of the four molecular shapes with 5 electron domains/density regions, two will always be polar: T-shape and see-saw. This is because the lone pairs of each cause an asymmetrical arrangement (dipole moments won’...
by Ashley Ko 3I
Sun Nov 29, 2020 10:45 am
Forum: Lewis Structures
Topic: determining polarity
Replies: 5
Views: 44

Re: determining polarity

Hi! I agree with the above posts about electronegativity and dipole moments! I think it’s also helpful to look at the molecular shape and the types of atoms surrounding the central atom. For example, if all the atoms surrounding the central element are the same, then the molecule is most likely nonp...
by Ashley Ko 3I
Sun Nov 22, 2020 6:30 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Shape
Replies: 10
Views: 96

Re: Shape

I believe the molecular shape would be linear. Hope this helps!
by Ashley Ko 3I
Sun Nov 22, 2020 5:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Stable Geometry
Replies: 2
Views: 19

Re: Stable Geometry

Hi! Yes, I believe that a more stable geometry involves minimizing the amount of electron-electron repulsions. Hope this helps!
by Ashley Ko 3I
Sun Nov 22, 2020 5:46 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 21
Views: 128

Re: Bond Angles

Hi! I believe you don't need to know how to calculate bond angles. You just need to memorize the general bond angles and be able to determine based on the molecular shape how the bond angle changes. For example, lone pairs decrease the bond angle so for a molecule like H2O, which has 2 lone pairs, t...
by Ashley Ko 3I
Sun Nov 22, 2020 5:35 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling Week 7-8 #2
Replies: 3
Views: 34

Re: Sapling Week 7-8 #2

Hi! I agree with the above two posts. The molecular shape should be square planar since there are 6 electron domains (2 of which are lone pairs and the other 4 are bond domains). Hope this helps!
by Ashley Ko 3I
Sun Nov 22, 2020 12:24 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Week 7 Sapling: #5
Replies: 4
Views: 28

Re: Week 7 Sapling: #5

Hi! I believe axial atoms are those that line on the vertical axis/plane of the molecule and equatorial atoms are those that line on the horizontal axis/plane. Hope this helps!
by Ashley Ko 3I
Thu Nov 12, 2020 3:38 pm
Forum: Ionic & Covalent Bonds
Topic: Intramolecular vs Intermolecular
Replies: 4
Views: 45

Re: Intramolecular vs Intermolecular

Hi! So intermolecular means BETWEEN MOLECULES and intramolecular means WITHIN A MOLECULE. For instance, intermolecular forces occur between molecules (hydrogen bonding can occur between two H2O molecules). In contrast, covalent bonding occurs between two atoms in a molecule and is an example of an i...
by Ashley Ko 3I
Thu Nov 12, 2020 3:32 pm
Forum: Dipole Moments
Topic: H-Bonds
Replies: 14
Views: 132

Re: H-Bonds

Hi! To my understanding, hydrogen bonding occurs between a hydrogen atom of one molecule and one of three electronegative elements in another molecule (F, O, or N --> I memorize these elements as like fun or fon). The hydrogen atom of the first molecule must also be bonded to one of the three electr...
by Ashley Ko 3I
Thu Nov 12, 2020 3:15 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Memorizing Formula
Replies: 4
Views: 48

Re: Memorizing Formula

Hi! I guess an easier way of memorizing how to calculate formal charge is the following: Formal charge = # of valence electrons of the atom - number of electrons in lone pairs (electrons surrounding the atom) - number of bonds (so a single bond is equal to one and a double bond is equal to 2 etc.) T...
by Ashley Ko 3I
Thu Nov 12, 2020 3:09 pm
Forum: Ionic & Covalent Bonds
Topic: Dipole-Dipole and Ion-Dipole
Replies: 1
Views: 13

Re: Dipole-Dipole and Ion-Dipole

Hi! With dipole-dipole interactions, they occur between two polar molecules or molecules with dipole moments (a positively charged end and a negatively charged end). In contrast, with ion-dipole interactions, one of the two interacting entities is an ion while the other is a polar molecule. Hope thi...
by Ashley Ko 3I
Thu Nov 12, 2020 12:07 pm
Forum: Formal Charge and Oxidation Numbers
Topic: 2.A.13
Replies: 5
Views: 52

Re: 2.A.13

Hi! You could write out the electron configuration for each ground-state atom and see what orbital the outermost electron occupies (for atoms that are in the d-block, electrons would be removed from the s-subshell before the d-subshell since the s-subshell becomes of higher energy level once the d-s...
by Ashley Ko 3I
Sat Nov 07, 2020 10:02 pm
Forum: Quantum Numbers and The H-Atom
Topic: Magnetic Quantum Number
Replies: 3
Views: 25

Re: Magnetic Quantum Number

I agree with the above post. No, the order does not matter. I believe this is because the orbitals kind of fill up randomly since the energy of each orbital is about the same. Hope this helps!
by Ashley Ko 3I
Fri Nov 06, 2020 3:16 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizing Power
Replies: 5
Views: 40

Re: Polarizing Power

Hi! So the greater the polarizing power of a cation, the greater the covalent character in a bond because there would be a greater shared region between the cation and anion. As for the silver halide example, as the size of the anion increased, so did the covalent character. This is because an incre...
by Ashley Ko 3I
Thu Nov 05, 2020 2:21 pm
Forum: Quantum Numbers and The H-Atom
Topic: ml and number of possible electrons
Replies: 6
Views: 54

Re: ml and number of possible electrons

Yes, if ml is specified but not ms, then there are two electrons possible with the same ml quantum number. This is because ml refers to a specific orbital and orbitals can only have a maximum of two electrons. Hope this helps!
by Ashley Ko 3I
Wed Nov 04, 2020 12:27 pm
Forum: Octet Exceptions
Topic: Figuring out expanded valence shells
Replies: 2
Views: 22

Re: Figuring out expanded valence shells

Hi! Elements with an energy state of n = 3 or greater can have expanded octets. The important point is that for n = 3 or greater energy states, there are d-subshells available, allowing elements to have more than 8 electrons. Hope this helps!
by Ashley Ko 3I
Tue Nov 03, 2020 2:09 am
Forum: Resonance Structures
Topic: Resonance for Sulfate Ion
Replies: 3
Views: 34

Re: Resonance for Sulfate Ion

Hi! So, I believe that for elements with energy levels/states equal to or greater than n = 3, there is a general rule that expanded octets can have a maximum of 12 electrons. Hope this helps!
by Ashley Ko 3I
Sun Nov 01, 2020 12:13 pm
Forum: Quantum Numbers and The H-Atom
Topic: ml in quantum numbers
Replies: 3
Views: 37

Re: ml in quantum numbers

Hi! So, the quantum number, ml, refers to a specific orbital. It is related to l in that the range of ml is -l to +l. For example, if l = 2, then the ml can be -2, -1, 0. +1, or +2 (this makes sense since l = 2 refers to the d-subshell, which has 5 orbitals). As for electron spin, every orbital has ...
by Ashley Ko 3I
Sat Oct 31, 2020 4:50 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Sapling Homework
Replies: 8
Views: 57

Re: Sapling Homework

Hi! I would try what the above response said and also take out the commas. Hope this helps!
by Ashley Ko 3I
Sat Oct 31, 2020 4:45 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Sapling #21
Replies: 3
Views: 50

Re: Sapling #21

I think it would be helpful to use a periodic table to help you determine the number of electrons. For instance, memorize where the s, p, d, and f blocks are. In general though, I believe the main things you need to know are the following: n refers to the energy state, l refers to the subshell (if l...
by Ashley Ko 3I
Sat Oct 31, 2020 4:21 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: N levels for electron configurations
Replies: 6
Views: 62

Re: N levels for electron configurations

The quantum number, l, refers to the various subshells. For instance, when l = 0, it is referring to the s-subshell. In this case, since l = 1, it is referring to the p-subshell (5p). As a result, the number of electrons that can be in n = 5, l = 1 should be 6. Hope this helps! Also, by specifying t...
by Ashley Ko 3I
Sat Oct 31, 2020 11:20 am
Forum: Ionic & Covalent Bonds
Topic: Salt
Replies: 4
Views: 37

Re: Salt

Hi! So, I believe salts typically consist of a metal and a nonmetal. However, salts can also be made up of in general a cation and an anion (ionic bond). I think that (NH4)SO4 is considered a salt because the chemical bonds in (NH4)SO4 are considered ionic (NH4 is a cation with a charge of 1+ and SO...
by Ashley Ko 3I
Fri Oct 30, 2020 3:42 pm
Forum: Properties of Electrons
Topic: Sapling #11
Replies: 6
Views: 98

Re: Sapling #11

The quantum number, l, basically represents the different possible subshells, such as s, p, d, and f. The maximum value for l is n-1. For example, when n=3, the maximum value for l is 2 (this makes sense because the n=3 energy level has 3 possible subshells - 3s, 3p, and 3d). There are also some gen...
by Ashley Ko 3I
Wed Oct 28, 2020 5:36 pm
Forum: Empirical & Molecular Formulas
Topic: Mass Percent Composition
Replies: 3
Views: 66

Re: Mass Percent Composition

Hi! If given mass percent composition, then you should convert the percentages to grams and then calculate the mol of each element to find the empirical/molecular formulas. However, if given the mass of each element (not percent mass composition), you can convert directly to mol and then find the em...
by Ashley Ko 3I
Sun Oct 25, 2020 10:24 pm
Forum: Properties of Light
Topic: Work function
Replies: 5
Views: 29

Re: Work function

If the problem indicates that the kinetic energy of the electron is 0, then the energy you are finding would be the threshold energy or work function. In other words, you are finding threshold energy if you are just calculating the minimum energy required to eject the electron (no excess energy). Ho...
by Ashley Ko 3I
Fri Oct 23, 2020 1:10 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: h/4pi
Replies: 7
Views: 76

Re: h/4pi

Hi! So, I believe it is written as h/(4pi) because it is more accurate to do so. If you divide h by 4pi, you get a really long, complicated number and would have to round to write it as a constant. As a result, calculations would be less accurate. Hope this helps!
by Ashley Ko 3I
Fri Oct 23, 2020 1:02 am
Forum: Molarity, Solutions, Dilutions
Topic: Finding Formula of Unknown Molecule (Workshop)
Replies: 4
Views: 30

Re: Finding Formula of Unknown Molecule (Workshop)

Hi! I believe you made a mistake when converting the grams of H2O to grams of H. I think you may have forgotten to apply molar ratios (multiply by 2 after converting H2O to moles). You should get 0.060 g for H. For every 1 mol of H2O, there is 2 mol of H. For the empirical formula, I got C2H6O. Also...
by Ashley Ko 3I
Fri Oct 23, 2020 12:45 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic vs Molecular Spectroscopy
Replies: 2
Views: 13

Re: Atomic vs Molecular Spectroscopy

Hi! I think that all you need to know is that in both atomic and molecular spectroscopy, each element/molecule produces unique absorption/emission lines. Hope this helps!
by Ashley Ko 3I
Wed Oct 21, 2020 1:13 am
Forum: Properties of Electrons
Topic: Post Assesment Module: Wave Properties of Electrons and the De Broglie Equation Number 35
Replies: 6
Views: 76

Re: Post Assesment Module: Wave Properties of Electrons and the De Broglie Equation Number 35

The answer is no because the wavelength of large everyday objects, such as the electric car, is so small that it is immeasurable or unnoticeable. As a result, we say that they do not have wave-like properties because they follow the classic model. Hope this helps!
by Ashley Ko 3I
Wed Oct 21, 2020 1:08 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra
Replies: 2
Views: 27

Re: Atomic Spectra

Hi! I believe in one of Professor Lavelle's lectures, he mentions how the energy of the photon emitted is equal to but opposite in sign to delta E. The energy emitted by the electron (negative because reference level is 0) cancels out the energy of the emitted photon (positive). Hope this helps!
by Ashley Ko 3I
Tue Oct 20, 2020 4:36 pm
Forum: Limiting Reactant Calculations
Topic: Theoretical Yield
Replies: 12
Views: 127

Re: Theoretical Yield

I believe theoretical yield is typically in grams. Hope this helps!
by Ashley Ko 3I
Sun Oct 18, 2020 5:09 pm
Forum: Properties of Light
Topic: Work Function
Replies: 4
Views: 24

Re: Work Function

The kinetic energy is 0 when the energy of the photon is equal to the threshold energy (work function). There is kinetic energy when there is excess energy (energy of photon is greater than the threshold energy). According to the law of the conservation of energy, energy can neither be created nor d...
by Ashley Ko 3I
Sat Oct 17, 2020 2:33 am
Forum: Photoelectric Effect
Topic: Question about Short Wavelengths vs. Long Wavelengths
Replies: 6
Views: 83

Re: Question about Short Wavelengths vs. Long Wavelengths

So, the reason why shorter wavelengths can cause electrons to be ejected even at low intensities is because the energy of the photons is greater than or equal to the threshold energy (energy required to remove or eject an electron). The relationship between wavelength and energy can be seen through ...
by Ashley Ko 3I
Fri Oct 16, 2020 12:47 am
Forum: DeBroglie Equation
Topic: Homework Problem 1B.15
Replies: 3
Views: 27

Re: Homework Problem 1B.15

After solving part a and b, you should be able to find the kinetic energy and threshold energy (work function). As a result, you should be able to solve for the energy of the incident radiation by adding the kinetic energy and threshold energy (work function). In other words, you would rearrange E (...
by Ashley Ko 3I
Wed Oct 14, 2020 6:18 pm
Forum: Properties of Light
Topic: Relationship between energy of photon and energy to remove
Replies: 5
Views: 44

Re: Relationship between energy of photon and energy to remove

Yes, if the energy of the photons is greater than or equal to the threshold energy, then electrons will be ejected. If the energy of the photons is not sufficient to eject the electrons, then no matter how intense the light, no electrons will be ejected. As seen in the equation E = hv, the only way ...

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