Search found 92 matches

by Juliet Carr 1F
Sun Feb 21, 2021 1:20 am
Forum: Balancing Redox Reactions
Topic: coefficients for oxidation number
Replies: 21
Views: 74

Re: coefficients for oxidation number

The stoichiometric coefficients do not affect the oxidation number of individual elements or molecules, however it is important to consider them when calculating and balancing the reaction's overall charge.
by Juliet Carr 1F
Sun Feb 21, 2021 1:12 am
Forum: Balancing Redox Reactions
Topic: cool acronym
Replies: 25
Views: 95

Re: cool acronym

Yes I learned OILRIG too :) , and it clears up any confusion in case you were unsure of/ mixed up oxidation and reduction.
by Juliet Carr 1F
Sun Feb 21, 2021 1:02 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: anode and cathode L/R
Replies: 14
Views: 35

Re: anode and cathode L/R

I don't think it matters the side of the anode and cathode as it would be different for two people standing across from each other looking at the same cell diagram. The important thing to remember is that oxidation occurs at the anode, reduction occurs at the cathode, and electrons flow from the ano...
by Juliet Carr 1F
Sat Feb 20, 2021 6:51 pm
Forum: Balancing Redox Reactions
Topic: First Lecture Galvanic Cell
Replies: 7
Views: 36

Re: First Lecture Galvanic Cell

The example used in lecture was the oxidation of zinc and reduction of copper. I don't think this example is specific to galvanic cells. Though I think the requirements for the substances used in galvanic cells are that two different metals are used, oxidation occurs at the anode, reduction occurs a...
by Juliet Carr 1F
Sat Feb 20, 2021 6:25 pm
Forum: Balancing Redox Reactions
Topic: Salt Bridges
Replies: 21
Views: 41

Re: Salt Bridges

The purpose of the salt bridge is to allow for ion transfer so that the solutions remain neutral.
by Juliet Carr 1F
Fri Feb 12, 2021 11:46 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Textbook 4.15
Replies: 1
Views: 19

Re: Textbook 4.15

This question is confusing because it doesn't make it clear to refer to the table of enthalpies of formation given in the textbook. Once you have written out the chemical equation of the reaction, you can use the equation: (sum deltaHf[products]) - (sum deltaHf[reactants] ) and the values given in t...
by Juliet Carr 1F
Fri Feb 12, 2021 11:36 pm
Forum: Calculating Work of Expansion
Topic: Integral Equations
Replies: 6
Views: 22

Re: Integral Equations

I think Dr. Lavelle wrote the equation sheet so that the integral part is shown, then the same equation not involving calculus is written out next to it. I think the integral equations are shown so that we can relate the equation we are using to its initial derivation.
by Juliet Carr 1F
Fri Feb 12, 2021 11:26 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Residual entropy
Replies: 4
Views: 24

Re: Residual entropy

On the basis of structure, only NO and N2O would be likely to have residual entropy. Cl2 and CO2 would not have residual entropy because both of these molecules are symmetrical, so orienting the molecules in different ways does not contribute to increased disorder. Both NO and N2O could be ordered i...
by Juliet Carr 1F
Fri Feb 12, 2021 11:18 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: sapling #9
Replies: 2
Views: 27

Re: sapling #9

In order to calculate the change in entropy of the system, you can use the equation (sum of standard molar entropy of products) - (sum of standard molar entropy of reactants) using the values linked where is says "refer to standard entropy values as needed". Next, to find the change in ent...
by Juliet Carr 1F
Fri Feb 12, 2021 11:09 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: When to use molar heat capacities of liquid or vapor.
Replies: 2
Views: 11

Re: When to use molar heat capacities of liquid or vapor.

Since the question is asking to calculate the entropy of vaporization at a temperature other than the boiling point and entropy is a state function, you need to calculate the entropy at three different points and add them together. The first calculation is the change in entropy heating the water to ...
by Juliet Carr 1F
Sun Feb 07, 2021 1:05 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Sapling #14
Replies: 5
Views: 55

Re: Sapling #14

Hi! For path A, the question says that it is an isothermal, reversible expansion. So we use the equation w = -nRTln(V2/V1). We have the V2 and V1 given in the equation (V2 = 8.96L, V1 = 2.84L), and we also have the T (298K) and the R which is a constant. So, we need to calculate the number of moles...
by Juliet Carr 1F
Sun Feb 07, 2021 12:50 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: solving for q (grams vs mol)
Replies: 5
Views: 29

Re: solving for q (grams vs mol)

In the textbook problems, we used Cp and Cv as heat capacities for ideal gasses. Cp is the heat capacity of an ideal gas at constant pressure, and Cv at constant volume. According to the constants and equations sheet, Cp for an ideal gas = (5/2)R and Cv = (3/2)R. Section 4C in the textbook better de...
by Juliet Carr 1F
Sun Feb 07, 2021 12:39 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Sapling Week 3/4 #13
Replies: 8
Views: 39

Re: Sapling Week 3/4 #13

Work can be described by the equation w = -(delta(n))RT, where negative work indicates work done by the system onto the surroundings. So in order to find the equation that represents work done onto the surroundings (-w), delta(n) needs to be a positive value. Also it is important that when calculati...
by Juliet Carr 1F
Mon Feb 01, 2021 8:05 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimeters
Replies: 15
Views: 75

Re: Calorimeters

I think it'll definitely be helpful to have a strong understanding of calorimeters and for the most part, have the diagram memorized. Hannah's explanation above about the bathtub is a great trick to use! What exactly is the purpose of a calorimeter? The purpose of a calorimeter is to measure the tr...
by Juliet Carr 1F
Mon Feb 01, 2021 7:55 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Sapling Week 3/4 #18
Replies: 2
Views: 23

Re: Sapling Week 3/4 #18

Sapling writes this for the relationship between Cv and Cp: "The change in internal energy deltaU that corresponds to a temperature change deltaT is given by deltaU=n(Cv)(deltaT) where Cv is the constant‑volume molar specific heat of the gas. Cv is related to Cp by (CV = CP-R) = (5R/2 - R) = (3...
by Juliet Carr 1F
Fri Jan 29, 2021 10:20 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy Reactions
Replies: 13
Views: 48

Re: Enthalpy Reactions

It also depends on the information given and the specific problem being solved. For example, a requirement for calculating bond enthalpies is that the substances are in gas state. If this is not the case, and the substance is in a different state you also have to consider the enthalpy involved with ...
by Juliet Carr 1F
Fri Jan 29, 2021 10:14 pm
Forum: Phase Changes & Related Calculations
Topic: reaction shifts
Replies: 18
Views: 82

Re: reaction shifts

Things to remember with endothermic and exothermic reactions in equilibrium: Endothermic (+): Increasing the temperature/adding heat shifts towards production of products Decreasing the temperature/cooling shifts towards production of reactants Exothermic (-): Increasing temperature shifts towards p...
by Juliet Carr 1F
Fri Jan 29, 2021 10:05 pm
Forum: Phase Changes & Related Calculations
Topic: Heat vs Enthalpy State property?
Replies: 5
Views: 38

Re: Heat vs Enthalpy State property?

To my understanding, heat depending on the path refers to the heat/energy transferred between the system and surroundings during some heat exchange process. Since this exchange depends on the ways in which the process occurs, heat cannot be a state function.
by Juliet Carr 1F
Fri Jan 29, 2021 9:57 pm
Forum: Phase Changes & Related Calculations
Topic: endothermic/exothermic
Replies: 43
Views: 155

Re: endothermic/exothermic

You can also tell if a certain phase change is endothermic or exothermic based on whether the original substance was heated or cooled to complete the phase change. If the substance is heated, such as ice to water (solid to liquid), this is endothermic. If a substance is cooled, such as gas to liquid...
by Juliet Carr 1F
Fri Jan 29, 2021 9:53 pm
Forum: Phase Changes & Related Calculations
Topic: Examples of sublimation
Replies: 12
Views: 72

Re: Examples of sublimation

I've also read that substances with caffeine can be purified through processes including sublimation.
by Juliet Carr 1F
Sat Jan 23, 2021 11:46 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Week 3 Sapling #5
Replies: 4
Views: 40

Re: Week 3 Sapling #5

With questions involving Hess' law I would say the most important things to remember are: -if you flip the chemical equation, change the sign of the enthalpy value -if you multiply the whole equation by a coefficient, multiple the enthalpy value by the same coefficient -make sure all the required co...
by Juliet Carr 1F
Sat Jan 23, 2021 11:24 pm
Forum: Phase Changes & Related Calculations
Topic: Bond Enthalpies
Replies: 4
Views: 16

Re: Bond Enthalpies

I think using bond enthalpies is just one of the three methods used to calculate the change in enthalpy of a reaction. The three main methods discussed in lecture were using Hess' method, bond enthalpies, or standard reaction enthalpies such as enthalpy of formation. In terms of those three methods,...
by Juliet Carr 1F
Sat Jan 23, 2021 11:16 pm
Forum: Phase Changes & Related Calculations
Topic: Define Phase Change
Replies: 76
Views: 217

Re: Define Phase Change

I think a phase change is just a change in the state of matter.
For example:
-When you heat liquid water, it undergoes a phase change from liquid to gas
-When you cool liquid water, it undergoes a phase change from liquid to solid
-etc.
by Juliet Carr 1F
Sat Jan 23, 2021 11:06 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Qudratic Formula
Replies: 19
Views: 106

Re: Qudratic Formula

I would also suggest graphing the quadratic equation on your calculator and then finding the zeros that way for the values of x because it is very easy to make mistakes when inputing the quadratic formula on a calculator due to signs, correct parentheses use, square root, etc.
by Juliet Carr 1F
Thu Jan 21, 2021 8:15 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Week 2 Sapling #5
Replies: 9
Views: 68

Re: Week 2 Sapling #5

I don't think you should disregard the x in this question since you need to solve for the initial concentration in order to find the percent protonation. Also, a way to check if u can disregard the x is if you get an answer 5% or greater because in that case you are unable to approximate.
by Juliet Carr 1F
Thu Jan 21, 2021 8:05 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Equilibrium Adjustments
Replies: 10
Views: 67

Re: Equilibrium Adjustments

Adding onto what others have already said, you can think of the equilibrium chemical reaction like a scale that wants to be balanced. For example, if the equilibrium is disturbed by adding more product, the reaction will shift to the production of reactants as if it was evening back out the scale. S...
by Juliet Carr 1F
Sat Jan 16, 2021 11:39 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Pressure Rule
Replies: 29
Views: 220

Re: Pressure Rule

When changing the pressure of a system make sure to only focus on the moles of gas to see the effects on the reaction. Do not account for the moles of solid, liquid, or aqueous compounds when examining the effects of altering the pressure/ volume.
by Juliet Carr 1F
Sat Jan 16, 2021 11:18 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle with Temperature
Replies: 7
Views: 27

Re: Le Chatelier's Principle with Temperature

When Dr. Lavelle was explaining this concept he showed the potential energy diagrams for an endothermic versus exothermic reaction. The endothermic reactions had reactants lower than products with a positive enthalpy (moving left to right on the graph), and the exothermic reaction had reactants high...
by Juliet Carr 1F
Sat Jan 16, 2021 10:52 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pka and ka
Replies: 5
Views: 45

Re: pka and ka

In general: -pH is the -log[hydrogen ion concentration] -Ka is the acidity constant for the equilibrium reaction of a weak acid in solution [products/reactant, or in many cases (hydronium ion concentration)x(conjugate base concentration)/ (weak acid concentration)] -pKa is just the -log[Ka] -Both pK...
by Juliet Carr 1F
Sat Jan 16, 2021 10:36 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: today's lecture
Replies: 8
Views: 43

Re: today's lecture

so i understand that if the equilibrium constant is less than 10^-4, approximation is okay. i am a bit confused/curious though as to why 10^-4 is the baseline or value that allows for approximation. is that just something memorize or is there reasoning behind it? To add onto what someone else said,...
by Juliet Carr 1F
Sat Jan 16, 2021 10:17 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Using the ICE table
Replies: 36
Views: 127

Re: Using the ICE table

Yes! The same process for finding either the initial, change, or equilibrium concentrations using an ICE table can also be used for finding pressure amounts.
by Juliet Carr 1F
Sun Jan 10, 2021 10:40 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook Problem 5I.13
Replies: 2
Views: 31

Re: Textbook Problem 5I.13

You need to use an ICE table. You know the Kc value from Table 5G.2. Plug all the expressions from the ICE table into the Kc expression and set it equal to the value from Table 5G.2. Using the quadratic formula, solve for x. Knowing this x value, you will be able to evaluate the concentrations at e...
by Juliet Carr 1F
Wed Jan 06, 2021 10:42 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Equilibrium Constant in Le Chatelier's
Replies: 3
Views: 31

Re: Equilibrium Constant in Le Chatelier's

Yes only a change in temperature will change the value of K. When there is a change in the amount of reactant or product, the chemical reaction will readjust itself to reach equilibrium again, and when it does the ratio of concentrations of products to reactants remains the same. Similarly, the orig...
by Juliet Carr 1F
Tue Jan 05, 2021 10:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Chemical Equilibrium 1A Question 18
Replies: 3
Views: 42

Re: Chemical Equilibrium 1A Question 18

Like others have said, the answer would be B. Right away you are able to eliminate answers C and D. This is because the equilibrium constant (K) is calculated using equilibrium concentrations, instead of initial concentrations. If the concentrations are not those when the reaction has reached equili...
by Juliet Carr 1F
Tue Jan 05, 2021 10:13 pm
Forum: Ideal Gases
Topic: Conditions for PV=nRT
Replies: 5
Views: 35

Re: Conditions for PV=nRT

To answer the second question, the ideal gas law equation can be manipulated in order to find concentration or pressure to eventually find Kc or Kp.
For example:
PV=nRT, becomes
P=(n/V)RT, where (n/V) is concentration. So,
P=(conc.)RT
by Juliet Carr 1F
Tue Jan 05, 2021 10:05 pm
Forum: Ideal Gases
Topic: Units of Temperature
Replies: 82
Views: 348

Re: Units of Temperature

You would use kelvin as it is the SI unit for temperature.
by Juliet Carr 1F
Tue Jan 05, 2021 9:15 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Reactant in Excess
Replies: 9
Views: 75

Reactant in Excess

In module 4, we learned that when more of a reactant is added, more product will form until the original product/reactant ratio is attained.

I was wondering if there would be any effect on the chemical reaction if you added more of the reactant that was already in excess?

Thanks :)
by Juliet Carr 1F
Sat Dec 12, 2020 6:45 pm
Forum: Identifying Acidic & Basic Salts
Topic: 6D.11 part e and f
Replies: 2
Views: 48

Re: 6D.11 part e and f

I think the answer key shows Al(H2O)6^3 and Cu(H2O)6^2 to show how the reaction of the cation that makes up the salt (the conjugate acids of the weak bases) interacts with the solution to affect the pH.
by Juliet Carr 1F
Sat Dec 12, 2020 6:23 pm
Forum: Naming
Topic: 9C question 5
Replies: 4
Views: 34

Re: 9C question 5

Oxalate follows the general formula lone pair - spacer - spacer - lone pair, so it can be a polydentate ligand. In this case, it is a bidentate ligand because the two -1 charged oxygens can make coordinate covalent bonds with two transition metals, or form a chelate bonding to the same transition me...
by Juliet Carr 1F
Sat Dec 12, 2020 6:18 pm
Forum: Naming
Topic: en, dien, edta, etc.
Replies: 2
Views: 31

Re: en, dien, edta, etc.

Yes I think it is important to know the following things about the ligands: -en is a neutral, bidentate ligand -dien is a neutral, tridentate ligand -oxalato is a 2- charge, bidentate ligand -edta is a 4- charge, hexadentate ligand In general, anything on the naming coordination compounds worksheet ...
by Juliet Carr 1F
Sat Dec 12, 2020 6:10 pm
Forum: Naming
Topic: Polyatomic Ions for Coordination Compound Naming
Replies: 1
Views: 12

Re: Polyatomic Ions for Coordination Compound Naming

Yes I think we are expected to memorize all of the ligands and their ion charges on the naming coordination compounds worksheet on the class website.
by Juliet Carr 1F
Sat Dec 12, 2020 12:08 pm
Forum: Calculating the pH of Salt Solutions
Topic: Solving PH/PoH
Replies: 11
Views: 98

Re: Solving PH/PoH

I think the important takeaways from solving problems with PH and POH are:
[H3O+][OH-] = 1 x 10^-14
pH + pOH = 14
pH = -log[H3O+]
pOH = -log[OH-]

So being able to apply these concepts and doing the textbook problems are probably sufficient enough.
by Juliet Carr 1F
Sat Dec 05, 2020 3:10 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 9C 5b- Label the kind of ligand it is
Replies: 1
Views: 20

Re: 9C 5b- Label the kind of ligand it is

The carbonate ion is a monodentate ligand when one of the single bonded oxygens with -1 charge makes a coordinate covalent bond with a transition metal. It is a bidentate ligand when both of the single bonded oxygens with -1 charge make a coordinate covalent bond to the same transition metal in a ri...
by Juliet Carr 1F
Wed Dec 02, 2020 11:16 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Dentates
Replies: 3
Views: 56

Re: Dentates

In addition to drawing the structure out, I think it would be helpful to memorize whether common ligands are mono, di, tri, polydentate etc. Also, it would be beneficial to remember the formation lone pair - spacer - spacer - lone pair for polydentate ligands. Another rule when determining the numbe...
by Juliet Carr 1F
Wed Dec 02, 2020 10:58 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 9C.5 Question
Replies: 4
Views: 46

Re: 9C.5 Question

To add onto what others have said, in a UA session they said you can also typically tell if a ligand is polydentate if it follows the form: lone pair - spacer - spacer - lone pair.
by Juliet Carr 1F
Wed Dec 02, 2020 10:44 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxidation Numbers
Replies: 3
Views: 25

Re: Oxidation Numbers

Yes, your thought process is correct :) This same thought process can be also be applied to any element in groups 1-8, just not the transition metals. For example, you can assume a halogen has a -1 oxidation number, an alkali earth metal +2, and alkali metal +1, etc. Then, you multiply these oxidati...
by Juliet Carr 1F
Mon Nov 30, 2020 10:00 pm
Forum: Hybridization
Topic: Sigma and Pi bonds
Replies: 21
Views: 184

Re: Sigma and Pi bonds

Some differences between sigma and pi bonds include their formation. Sigma bonds form when two orbitals each with one electron overlap end-to-end. This overlap can occur between two s orbitals, s and p, p and p, etc. The overlap of orbitals in a sigma bond creates electron density with cylindrical s...
by Juliet Carr 1F
Mon Nov 30, 2020 9:28 pm
Forum: Hybridization
Topic: How to simply determine hybridization
Replies: 27
Views: 214

Re: How to simply determine hybridization

Like others have said, you should first count the regions of electron density around the central atom in question. Single bonds, double bonds, and triple bonds count as one region of electron density. Lone pairs also count as one region of electron density. Then, that number corresponds to the hybri...
by Juliet Carr 1F
Sun Nov 29, 2020 11:03 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bent Shape molecules
Replies: 7
Views: 79

Re: Bent Shape molecules

A molecule forms a bent shape when it either has three total regions of electron density with 2 regions bonded and one lone pair, or four total regions of electron density with 2 regions bonded and 2 lone pairs. The bent shape of the molecule is due to the greater repulsion strength of the lone pair...
by Juliet Carr 1F
Sun Nov 29, 2020 10:54 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling HW #18
Replies: 7
Views: 62

Re: Sapling HW #18

When they ask about relative positions, I think they are talking about the positions of atoms in relation to one another in a 3D space, using the lewis structure to help create the model. Lewis structures are 2D, but the actual model of the molecule is in 3D. For instance, the lewis structure for C...
by Juliet Carr 1F
Sun Nov 29, 2020 10:46 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelating Ligands
Replies: 4
Views: 56

Re: Chelating Ligands

Yes you are correct! In this example, the acetate ion is formed when the H is lost from the OH. This makes the single bonded oxygen a -1 charge, and now electron rich. Two acetate ions are able to bond to each of the N in ethylene, which are both also electron rich with a lone pair. So, the final st...
by Juliet Carr 1F
Sun Nov 29, 2020 10:12 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Number and Regions of density
Replies: 8
Views: 54

Re: Coordination Number and Regions of density

Based on how it was described in the lecture, I think coordination number has to do with the number of bonds instead of general regions of electron density, and does not include lone pairs.
by Juliet Carr 1F
Sun Nov 29, 2020 10:06 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligands
Replies: 4
Views: 31

Re: Ligands

Electron rich species are those that have valence lone pairs that can be donated. Some examples of electron rich species are negatively charged ions and lewis bases.
by Juliet Carr 1F
Sun Nov 22, 2020 5:02 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling Week 7 & 8 HW Question 10
Replies: 4
Views: 41

Re: Sapling Week 7 & 8 HW Question 10

I think the answer is referring to the molecule as a whole and the net vectors. For example in COF2 the vectors point towards the oxygen and two fluorine atoms because they are more electronegative compared to the carbon. However, since the electronegativity difference between carbon and fluorine is...
by Juliet Carr 1F
Sun Nov 22, 2020 4:44 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar bonds
Replies: 8
Views: 40

Re: Polar bonds

Hi, going off of this, I understand how to determine the polarity of a molecule but I am a little confused how to determine if an individual bond is polar or non-polar. Is it simply a large difference in electronegativity between the two atoms? My understanding of individual bonds being polar is th...
by Juliet Carr 1F
Tue Nov 17, 2020 8:46 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Group 5 transition metals
Replies: 2
Views: 23

Re: Group 5 transition metals

Oh I understand. Thank you for clarifying!
by Juliet Carr 1F
Mon Nov 16, 2020 10:48 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Textbook Problem 1E.5
Replies: 2
Views: 20

Re: Textbook Problem 1E.5

I think it is because the s orbital is closer to the nucleus than the p orbital. So the electrons in the s orbital experience a greater effective nuclear charge than the electrons in the p orbital as the p orbital is further away from the nucleus and the electrons in s orbital shield some of that ch...
by Juliet Carr 1F
Mon Nov 16, 2020 10:44 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Counting Valence Electrons D Orbital Vs S and P Orbitals
Replies: 3
Views: 26

Re: Counting Valence Electrons D Orbital Vs S and P Orbitals

I had the same question about this problem. I'm thinking maybe Mn includes the valence electrons in the d block because it falls in the d block of the periodic table. Then for Sb they don't include the valence electrons in the 4d subshell because Sb doesn't exist in the d block on the periodic table...
by Juliet Carr 1F
Mon Nov 16, 2020 10:31 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Group 5 transition metals
Replies: 2
Views: 23

Group 5 transition metals

Textbook problem 1E.25 b) says to give the notation for valence shell configuration (including outermost d electrons) of Group 5 transition metals. The answer given was (n-1)d^5 ns^2. It appears that (n-1)d^5 ns^2 gives the valence shell configuration for group 7 on the periodic table which includes...
by Juliet Carr 1F
Sun Nov 15, 2020 10:17 am
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR
Replies: 11
Views: 116

Re: VSEPR

It is really important to consider VSEPR when determining polarity because VSEPR will show symmetry in the shape of the molecule. So, if there are unequal pulls on the central atom in different directions by the dipole moments surrounding it, then the dipole moments cannot cancel and the molecule is...
by Juliet Carr 1F
Sun Nov 15, 2020 10:07 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Textbook #3F1
Replies: 4
Views: 47

Re: Textbook #3F1

The partial negative exists on the more electronegative atom, and in this example that is oxygen. So the oxygen exists as partially negative making the S exists as partially positive. This creates two dipole moments, and the reason why these moments do not cancel out is because of the lone pair elec...
by Juliet Carr 1F
Sun Nov 15, 2020 10:00 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Interaction potential energy application?
Replies: 2
Views: 13

Re: Interaction potential energy application?

I think the important take aways from this equation is that the interaction potential energy (Ep) is inversely proportional to the radius. As the radius gets larger, the Ep gets smaller and vise versa. So, the molecules have to be close to one another in order to cause a strong interaction between t...
by Juliet Carr 1F
Sun Nov 15, 2020 9:52 am
Forum: Coordinate Covalent Bonds
Topic: When do we use it
Replies: 9
Views: 59

Re: When do we use it

Coordinate covalent bonds are also common between lewis acids and bases. Since lewis acids are electron pair acceptors and lewis bases are electron pair donors, the lewis base will donate both of its electrons to form a coordinate covalent bond with the lewis acid.
by Juliet Carr 1F
Sun Nov 15, 2020 9:41 am
Forum: Coordinate Covalent Bonds
Topic: OH
Replies: 5
Views: 51

Re: OH

Ya it might seem like OH is a radical because if you add up the valence electrons to make the lewis structure it is 7e- (6e- from O and 1e- from H), which would leave one electron unpaired. However, OH exists as OH-, so a total of 8e- (6e- from O + 1e- from H + 1e-), making OH- not a radical.
by Juliet Carr 1F
Sun Nov 08, 2020 7:05 pm
Forum: Formal Charge and Oxidation Numbers
Topic: formal charge
Replies: 11
Views: 42

Re: formal charge

Formal charge definition states that it is the charge of an atom in a molecule, so it must be bonded to other atoms. Also if the atom was not bonded then there would be an important part of the formula missing, and it could not be calculated.
by Juliet Carr 1F
Sun Nov 08, 2020 7:01 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge, expanded octet
Replies: 4
Views: 25

Re: Formal Charge, expanded octet

For the exceptions to the octet rule it is more important to maintain a formal charge closer to zero. However when you are trying to draw the correct lewis structure it is important to make sure that all the elements follow the octet rule first (for example that's why we sometimes have to make singl...
by Juliet Carr 1F
Sun Nov 08, 2020 6:36 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Energy Levels in electron configurations
Replies: 5
Views: 31

Re: Energy Levels in electron configurations

If you follow the periodic table you can see that from left to right the 4s subshell comes before the 3d subshell. So when you are adding electrons to elements after Ar the 4s is filled first, but once Sc is reached and electron are added to the 3d subshell it has lower energy than 4s and it written...
by Juliet Carr 1F
Sun Nov 08, 2020 6:25 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 2A.11 Question
Replies: 2
Views: 15

Re: 2A.11 Question

How I would approach this problem: 1)Since it is asking for a metal then it would narrow my answer mostly to elements in the s or d block, and some of the p block. 2)Also since it says its a 3+ ion that means 3 electrons were lost from the metal in question. 3)Then I would look at the electron confi...
by Juliet Carr 1F
Sun Nov 08, 2020 5:48 pm
Forum: Ionic & Covalent Bonds
Topic: Size of Bonds
Replies: 28
Views: 102

Re: Size of Bonds

The nucleus interacts with more electrons in double bonds than in single bonds, so it is able to pull the electrons closer resulting in shorter bonds.
by Juliet Carr 1F
Fri Oct 30, 2020 7:21 pm
Forum: Quantum Numbers and The H-Atom
Topic: Number of Electrons per Shell
Replies: 5
Views: 61

Re: Number of Electrons per Shell

I have not watched the lecture yet so I'm not completely sure what he's referring to but in general there is a formula 2n^2, where n is the principal quantum level/shell, and this formula gives the maximum amount of electrons that can occupy each shell.
by Juliet Carr 1F
Fri Oct 30, 2020 7:13 pm
Forum: Quantum Numbers and The H-Atom
Topic: M(l) Quantum Number
Replies: 5
Views: 55

Re: M(l) Quantum Number

I think m(l) itself is a quantum number, so I don't know if you could have three different quantum numbers for m(l), but instead you could have three different values for the quantum number m(l). I'm pretty sure if the last electron falls in in p(x) m(l) is -1, 0 for p(y), and 1 for p(z). So, I thin...
by Juliet Carr 1F
Fri Oct 30, 2020 7:01 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity
Replies: 9
Views: 86

Re: Electron Affinity

In simple terms, I just think of electron affinity as the opposite of ionization energy. Ionization energy is a measure of the energy required to remove an electron from an atom. Instead, electron affinity is a measure of the energy required to put an electron in the outer shell of an atom.
by Juliet Carr 1F
Fri Oct 30, 2020 6:50 pm
Forum: Trends in The Periodic Table
Topic: Trends
Replies: 14
Views: 108

Re: Trends

Similar to what others have explained, as you move down a group the atomic and ionic radii increase. This is because more energy shells are being added to the atoms moving down the group to account for the increase in electrons. As additional energy shells are added, they are further away from the n...
by Juliet Carr 1F
Fri Oct 30, 2020 6:39 pm
Forum: Trends in The Periodic Table
Topic: ionization trend
Replies: 3
Views: 40

Re: ionization trend

The elements on the periodic table with 'low' first ionization energy values (compared to the other elements) are metals, and metals conduct electricity well. So, that could be used to explain how low ionization energy ensures that atom conducts electricity. I'm sure there are other factors that can...
by Juliet Carr 1F
Fri Oct 23, 2020 6:04 pm
Forum: Photoelectric Effect
Topic: Sapling HW Weeks 2, 3, 4 Question #9
Replies: 10
Views: 105

Re: Sapling HW Weeks 2, 3, 4 Question #9

To the above question about how to know if the sparks were caused by the photoelectric effect or not (I don't know how to reply to a reply lol): There should be second part to the question that gives the frequency that the microwave radiates. Then, convert that number to wavelength, and if the wavel...
by Juliet Carr 1F
Fri Oct 23, 2020 5:46 pm
Forum: Photoelectric Effect
Topic: Application
Replies: 5
Views: 44

Re: Application

Similar to what other students have explained, the photoelectric effect can only work on metals because of the nature of metallic bonds. Metallic bonds create a 'sea of electrons', which can be easily emitted from the metal when the energy of the photons in the light shone is greater than or equal t...
by Juliet Carr 1F
Fri Oct 23, 2020 5:38 pm
Forum: DeBroglie Equation
Topic: Sapling #22
Replies: 11
Views: 112

Re: Sapling #22

In this case you cannot use E = hv to solve for the e-s kinetic energy because this equation is used to solve for the energy of one photon. The kinetic energy of the electron is the energy of the photon minus the threshold energy. The kinetic energy can be calculated using the equation Ek = 1/2(m)(v...
by Juliet Carr 1F
Fri Oct 23, 2020 4:07 pm
Forum: *Black Body Radiation
Topic: Midterm 1
Replies: 15
Views: 293

Re: Midterm 1

I don't think we need to know black body radiation for the exam because Lavelle has mentioned multiple times that we won't be going into detail about it, however, I think it would be good to have a general understand of a black body being an object that absorbs and emits all frequencies of radiation...
by Juliet Carr 1F
Fri Oct 23, 2020 4:00 pm
Forum: Einstein Equation
Topic: Scratch paper during the exam
Replies: 19
Views: 154

Re: Scratch paper during the exam

My TA said you can use the front an back of the constants and periodic table sheets and as much scratch paper as you need as long as you show the front and back of every paper before the exam begins.
by Juliet Carr 1F
Fri Oct 23, 2020 3:57 pm
Forum: Properties of Light
Topic: Energy and intensity of light in both models
Replies: 4
Views: 55

Re: Energy and intensity of light in both models

In one of the workshop sessions a UA mentioned that in a classical wave model increasing the intensity means increasing the amplitude, and increasing the amplitude of a wave usually means higher energy. Although, I'm not sure if this relationship can be used to describe the wave model of light becau...
by Juliet Carr 1F
Fri Oct 16, 2020 9:04 pm
Forum: Einstein Equation
Topic: E=hv
Replies: 8
Views: 102

Re: E=hv

The equation is -hR/n^2 with the negative sign meaning that bound electrons have lower energy than free electrons. The question was asking to calculate frequency of light emitted by an H-atom when an electron makes a transition from the fourth to the second principal quantum level. Since the electro...
by Juliet Carr 1F
Wed Oct 14, 2020 3:44 pm
Forum: Properties of Light
Topic: Textbook Problem 1A. 3
Replies: 7
Views: 89

Re: Textbook Problem 1A. 3

Similar to another response, I interpreted extent of change as relating to the amplitude and size/width of the wave. So, if frequency decreases, then wavelength has increased. Now within a certain region, the wave extends bigger than it did when the frequency was increased in this region. So, within...
by Juliet Carr 1F
Wed Oct 14, 2020 3:32 pm
Forum: Properties of Light
Topic: Textbook question 1A.3
Replies: 3
Views: 26

Textbook question 1A.3

Which of the following happens when the frequency of electromagnetic radiation decreases? Explain your reasoning. (a) The speed of the radiation decreases. (b) The wavelength of the radiation decreases. (c) The extent of the change in the electrical field at a given point decreases. (d) The energy o...
by Juliet Carr 1F
Wed Oct 14, 2020 3:25 pm
Forum: Properties of Light
Topic: Memorization of Increasing Energy
Replies: 4
Views: 58

Re: Memorization of Increasing Energy

I think we are expected to know the order of electromagnetic radiation for tests and exams because there was a question about it in one of the topic 1A exercises that Lavelle assigned (not graded), and I remember the syllabus explaining how test/exam questions are directly related to homework proble...
by Juliet Carr 1F
Tue Oct 13, 2020 7:25 am
Forum: Properties of Light
Topic: Photoelectric effect
Replies: 8
Views: 77

Re: Photoelectric effect

Thank you everyone! Now I understand
by Juliet Carr 1F
Mon Oct 12, 2020 9:18 pm
Forum: Properties of Light
Topic: Photoelectric effect
Replies: 8
Views: 77

Photoelectric effect

In the lecture today (monday week 2) Lavelle wrote: "unless E(photon) is greater than or equal to E(energy to remove electron) then electron is not emitted even for high intensity light (this was unexpected)" I am having troubles understanding what this means, could someone please further ...
by Juliet Carr 1F
Fri Oct 09, 2020 9:48 pm
Forum: Molarity, Solutions, Dilutions
Topic: Fundamentals G.7
Replies: 2
Views: 23

Re: Fundamentals G.7

I think "describe how you would prepare this solution" is asking you to describe the steps to do this as if you were performing the experiment in a lab. For example, I would begin by saying "use a balance to measure out 482.2g of water (510g solution contains 5.45% KNO3, so 94.55% of ...
by Juliet Carr 1F
Fri Oct 09, 2020 9:32 pm
Forum: Molarity, Solutions, Dilutions
Topic: What does mmol stand for?
Replies: 33
Views: 361

Re: What does mmol stand for?

mmol in the question stands for millimole which is 1x10^-3 of a mole. Any unit with the "m" in front of it stands for milli-unit, and is 1x10^-3 of that unit. Millimole is a smaller unit than mole, so there are 1000mmol in one mole.
by Juliet Carr 1F
Wed Oct 07, 2020 6:23 pm
Forum: Significant Figures
Topic: Sapling Question 2
Replies: 14
Views: 113

Re: Sapling Question 2

As others have already explained, the answer should be 2.917 x 10^2 instead of 2.917 x 10^-2. I would always make silly mistakes when putting numbers into scientific notation, so the way I liked to think about it was that if you move the decimal point to the left, it's like moving left on a number l...
by Juliet Carr 1F
Wed Oct 07, 2020 5:24 pm
Forum: SI Units, Unit Conversions
Topic: Formula Units
Replies: 8
Views: 68

Re: Formula Units

To add onto what other students have said, the textbook defines a formula unit as: "A group of ions having the number of atoms given by the formula". The textbook also states that the molar mass of an ionic compound = the mass per mole of its formula units. So I agree with others when they...
by Juliet Carr 1F
Tue Oct 06, 2020 6:10 pm
Forum: SI Units, Unit Conversions
Topic: Solving Average Molar Mass
Replies: 2
Views: 71

Re: Solving Average Molar Mass

To respond to the second part of your question, isotopes are two forms of the same element which have the same number of protons, but different number of neutrons. Hence, they have different mass numbers. An example of isotopes are carbon-12 and carbon-14. Both elements are carbon and have 6 protons...
by Juliet Carr 1F
Tue Oct 06, 2020 5:50 pm
Forum: Administrative Questions and Class Announcements
Topic: Posting during the weekends
Replies: 7
Views: 63

Posting during the weekends

The class website says we need to post to chemistry community 5 times per weeks to get maximum participation points. Does this only include the days of the school week, or can we also post on the weekends and receive points?

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