Search found 100 matches
- Mon Mar 15, 2021 3:30 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Specific Heat
- Replies: 9
- Views: 536
Re: Specific Heat
Heat capacity is the ratio of the amount of heat energy transferred to an object to the resulting increase in its temperature. (J/K) Specific heat capacity is a measure of the amount of heat necessary to raise the temperature of one gram of a pure substance by one degree K. (J/gK) Specific heat capa...
- Mon Mar 15, 2021 3:27 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Isolated System
- Replies: 11
- Views: 677
Re: Isolated System
The closest one can get to an isolated system would be to use something like a bomb calorimeter. However, even a bomb calorimeter is not perfect adn there would inevitably be an escape of energy.
- Mon Mar 15, 2021 3:25 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Which R value to choose
- Replies: 13
- Views: 1363
Re: Which R value to choose
To help decide which R to use, I am always wary of the units at play. For PV=nRT it would make the most sense to use R = 0.08206 L.atm.K^-1.mol^-1
- Mon Mar 15, 2021 3:24 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Calorimeter
- Replies: 6
- Views: 471
Re: Calorimeter
For a system in a calorimeter, you would use q=mc delta T
where c is specific heat (K/Kg K)
where c is specific heat (K/Kg K)
- Mon Mar 15, 2021 3:20 pm
- Forum: Calculating Work of Expansion
- Topic: when is change in internal energy 0
- Replies: 10
- Views: 1700
Re: when is change in internal energy 0
For this question, change in internal energy is not equal to 0 because there is a change in volume. A change in volume indicated that work is being done and thus there must be a change in internal energy since U=q+w
- Sun Mar 07, 2021 11:03 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Internal Energy Calculation
- Replies: 5
- Views: 335
Re: Internal Energy Calculation
Yes, U=q if volume is constant because there is no work being done (w=0)
- Sun Mar 07, 2021 10:51 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Cut off for K to ignore x
- Replies: 7
- Views: 368
Re: Cut off for K to ignore x
When percent dissociation is less than 5%, then typically x is considered negligible.
- Sun Mar 07, 2021 10:49 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier's Principle
- Replies: 21
- Views: 759
Re: Le Chatelier's Principle
Mastering the questions given on the outlines regarding le Chatlier's principle would best prepare for the midterm according to the website information :-)
- Sun Mar 07, 2021 10:48 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Temperature Change
- Replies: 16
- Views: 701
Re: Temperature Change
Yes, for endothermic reactions, the k value increases when temperature increases. This website explains how temperature changes affect k: https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Equilibria/Le_C...
- Sun Mar 07, 2021 10:38 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Adding a gas
- Replies: 26
- Views: 949
Re: Adding a gas
Argon is an inert gas and does not react with the elements, therefore it does not affect the reaction.
- Sun Feb 28, 2021 10:41 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Tips for what gas constant to use
- Replies: 10
- Views: 564
Re: Tips for what gas constant to use
keeping track of the given units of the problem helps to determine with gas constant to use!
- Sun Feb 28, 2021 10:36 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat Capacity
- Replies: 10
- Views: 616
Re: Heat Capacity
We cannot always use specific heat capacity because the mass is not always given in problems. It depends on the context of the problem!
- Sun Feb 28, 2021 10:34 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Calibrating Calorimeter
- Replies: 6
- Views: 2599
Re: Calibrating Calorimeter
Calibrating a calorimeter means obtaining the heat capcity of the calorimeter so that it can be used for experiments!
- Sun Feb 28, 2021 10:32 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Isolated System
- Replies: 16
- Views: 867
Re: Isolated System
Changes can be made to an isolated system. What makes this system characteristics is that it's matter and energy is not exchanged with its surroundings.
- Sun Feb 28, 2021 10:29 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Bomb Calorimeter
- Replies: 14
- Views: 4247
Re: Bomb Calorimeter
A bomb calorimeter is considered an isolated system. This is because matter nor energy is being exchanged with the surroundings outside of the bomb calorimeter.
- Sun Feb 28, 2021 10:27 pm
- Forum: Balancing Redox Reactions
- Topic: Week8 Sapling #3
- Replies: 3
- Views: 252
Week8 Sapling #3
For a particular redox reaction, BrO− is oxidized to BrO−3 and Fe3+ is reduced to Fe2+. Complete and balance the equation for this reaction in basic solution. The phases are optional. Answer: BrO−+4OH−+4Fe3+ ⟶ BrO−3 + 4Fe2+ +2 H2O To solve for this, I added H2O and OH to balance out the oxygens. Whe...
- Sat Feb 20, 2021 5:42 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Sapling week 5/6 #20
- Replies: 14
- Views: 2028
Re: Sapling week 5/6 #20
For this question the inequalities are at the bottom of the graph, and the spontaneity is at the top of the graph!
- Sat Feb 20, 2021 5:40 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Sapling #3 HELP (week 5 and 6)
- Replies: 7
- Views: 484
Re: Sapling #3 HELP (week 5 and 6)
T is the temperature of the reaction! Typically this is given. Also, remember that in Gibbs free energy, that temperature is in kelvins and not celsius!
- Sat Feb 20, 2021 5:38 pm
- Forum: Ideal Gases
- Topic: Units for K
- Replies: 29
- Views: 1053
Re: Units for K
Great question! There are no units, because they all cancel out. If you were to make a fraction of products over reactants with the respective units (molarity)...you would find that they all cancel! This is because K is a ratio of products and reactions at equilibrium.
- Sat Feb 20, 2021 5:36 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Sapling Q3
- Replies: 5
- Views: 310
Re: Sapling Q3
To solve this problem, it was useful for me to remember the conceptuals behind entropy (S) and enthalpy (H). Entropy is the measure of "disorder", thus when going from liquid to gas...there is more disorder and thus an increase in entropy. To break the bonds to go from liquid to gas, energ...
- Sat Feb 20, 2021 5:34 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: entropy positive value
- Replies: 30
- Views: 1678
Re: entropy positive value
Entropy is always positive when looking at the entropy of the universe, as entropy and disorder is always increasing when looking at the system perspective of the universe.
- Sat Feb 20, 2021 5:31 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: R Constant
- Replies: 91
- Views: 4972
Re: R Constant
What helps in determining which R constant to use, is to be wary of the units that are being used!
- Sat Feb 20, 2021 5:30 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Sapling #3 HELP (week 5 and 6)
- Replies: 7
- Views: 484
Re: Sapling #3 HELP (week 5 and 6)
What helps me solve this problem is to remember the conceptuals behind entropy and enthalpy. Entropy is the measure of "disorder", thus when going from liquid to gas...there is more disorder and thus an increase in entropy. To break the bonds to go from liquid to gas, energy is required an...
- Thu Feb 18, 2021 4:47 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: 4a.5 Reversible expansion and work
- Replies: 2
- Views: 240
4a.5 Reversible expansion and work
A piston confines 0.200mol Ne(g) in 1.20L at 25 degrees Celsius. Two experiments are performed: a.) The gas is allowed to expand through an additional 1.20L against a constant pressure of 1.00 atm b.) The gas is allowed to expand reversibly and isothermally to the same final volume which process doe...
- Sun Feb 07, 2021 11:28 pm
- Forum: Calculating Work of Expansion
- Topic: Sapling #20 Weeks 3/4
- Replies: 3
- Views: 220
Re: Sapling #20 Weeks 3/4
NO2 is non-linear, so you would use the molar heat capacity for that (3R). Therefore c (molar heat capacity) = 3R, Where R is the last constant. for the first part of the question you would use q = mc delta t The m would be in moles since c is molar heat capacity. The moles are given, and using the ...
- Sun Feb 07, 2021 11:28 pm
- Forum: Calculating Work of Expansion
- Topic: Sapling #20 Weeks 3/4
- Replies: 3
- Views: 220
Re: Sapling #20 Weeks 3/4
NO2 is non-linear, so you would use the molar heat capacity for that (3R). Therefore c (molar heat capacity) = 3R, Where R is the last constant. for the first part of the question you would use q = mc delta t The m would be in moles since c is molar heat capacity. The moles are given, and using the ...
- Sun Feb 07, 2021 11:23 pm
- Forum: Calculating Work of Expansion
- Topic: Sapling week 3/4 #15
- Replies: 9
- Views: 492
Re: Sapling week 3/4 #15
To find the volume change you would use PV = nRT. However, it is significant to recognize that n = to moles of N2 (g) and not Na(s) or NaN3. You can find the moles of N2 via stoichiometry given the moles of NaN3.
- Sun Feb 07, 2021 11:22 pm
- Forum: Calculating Work of Expansion
- Topic: Reversible vs. Irreversible
- Replies: 4
- Views: 198
Re: Reversible vs. Irreversible
For reversible reactions, w = -nRT x ln(Vf/Vi) whereas w=-delta n x R x T for irreversible reactions.
- Sun Feb 07, 2021 11:12 pm
- Forum: Calculating Work of Expansion
- Topic: Sapling #19
- Replies: 2
- Views: 187
Re: Sapling #19
What is important is to recognize that the sum of the neutralization volumes is equal to the given information regarding the specific heat capacity. In your case it gives information on the specific heat capacity for 0.600 L. The next information is given 0.300 L HClO2 + 0.300 L NaOH = 0.600L This j...
- Sun Feb 07, 2021 11:02 pm
- Forum: Calculating Work of Expansion
- Topic: Sapling #14
- Replies: 11
- Views: 414
Re: Sapling #14
For path A, we need to know the number of moles (n). We find this by using PV=nRT Where P is given (2.54 atm), V is given (3.98L), T is given (298K) and R is the constant 0.0821 Latm/Kmol After solving for n, you would plug it into w=-nRT x ln(Vf/Vi) We use this specific equation because it is a rev...
- Sun Jan 31, 2021 11:29 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: State Function
- Replies: 22
- Views: 667
Re: State Function
Work is not a state function because a state function is a property whose value does not depend on the path taken to reach that specific value. Work depends on the path taken.
- Sun Jan 31, 2021 11:26 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: converting T to kelvin
- Replies: 46
- Views: 3189
Re: converting T to kelvin
I would look at the units for the problem involved! For example, if it is specific heat then you would know that Kelvin is necessary since specific heat includes kelvins.
- Sun Jan 31, 2021 11:24 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Inert gas
- Replies: 25
- Views: 1461
Re: Inert gas
Because inert gases are non-reactive, the partial pressures do not change when an inert gas is added to a system.
- Sun Jan 31, 2021 11:20 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Molar Heat Capacity
- Replies: 11
- Views: 281
Re: Molar Heat Capacity
Molar heat capacity is the amount of Energy necessary to change 1 mole of the substance by 1 Kelvin. If the given is only in moles, you can use either specific heat capacity by calculating the mass or by directly using moles given.
- Sun Jan 31, 2021 11:18 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Specific Heat Capacity
- Replies: 3
- Views: 229
Re: Specific Heat Capacity
Specific heat capacity is defined as the amount of heat required to raise the temperature of 1 kilogram of a substance by 1 kelvin (SI unit of specific heat capacity J kg−1 K−1). This is an intensive property because it is a property of matter that does not change as the amount of matter changes.
- Sun Jan 24, 2021 8:11 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Approximately x
- Replies: 18
- Views: 552
Re: Approximately x
Hello! Typically when K is lower than 10^-5, then it is a good gauge on whether or not to approximate. When the percent of ionization is less than 5%, then approximation of x can definitely be used. x is so small that its decrease from the original reactant concentration is negligible. However, the ...
- Sun Jan 24, 2021 8:08 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: approximating
- Replies: 10
- Views: 351
Re: approximating
x is so small that its decrease from the original reactant concentration is negligible. However, the final concentrations are significant to the K value that they cannot be neglected regardless of how small x is.
- Sun Jan 24, 2021 8:02 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling Question 3
- Replies: 8
- Views: 526
Re: Sapling Question 3
It helps to remember these formulas:
-log(Ka)=pKa, -log(Kb)= pKb
pKa + pKb = 14
Ka x Kb =10^-14
and pH+pOH=14
-log(Ka)=pKa, -log(Kb)= pKb
pKa + pKb = 14
Ka x Kb =10^-14
and pH+pOH=14
- Sun Jan 24, 2021 7:56 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: How to tell if a salt is acidic, basic or neutral
- Replies: 7
- Views: 1097
Re: How to tell if a salt is acidic, basic or neutral
I would memorize the strong acids and bases chart. There is also a chart of common weak acids and bases. That helps me determine if a salt is acidic or basic. However, as the precious answers explained it helps to remember this rule of thumb: if Ka > Kb, the ion is acidic; if Kb > Ka, the ion is bas...
- Sun Jan 24, 2021 7:50 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Quadratics when assumption can't be used
- Replies: 5
- Views: 194
Re: Quadratics when assumption can't be used
Hello! I tend to solve for the quadratic by finding the 0 on the graph. However, there was a time during sample where my answer for x was negative despite how many times I checked my work. However, once I used the quadratic formula I was able to solve for a positive x. Mathematically, I can't explai...
- Sat Jan 16, 2021 8:51 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier's Principle
- Replies: 19
- Views: 1201
Re: Le Chatelier's Principle
It helps me to understand Le Chatelier's principle as a way to maintain balance and equilibrium of a reaction. If there are too many products, then the reaction will produce more reactants. The reaction will shift from products and/or reactants depending on the changes that it experiences.
- Sat Jan 16, 2021 8:49 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Change in pressure due to inert gas
- Replies: 6
- Views: 183
Change in pressure due to inert gas
I understand that volume is the only change which has an effect on concentration and thus is the only change in pressure which has an effect in the direction of the reaction. However, wouldn't the addition of an insert gas change the individual partial pressure of products and reactants? And as a re...
- Sat Jan 16, 2021 8:46 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Neglecting Water
- Replies: 20
- Views: 957
Re: Neglecting Water
Pure solids or liquids are excluded from the equilibrium expression because their effective concentrations stay constant throughout the reaction. The concentration of a pure liquid or solid equals its density divided by its molar mass.
- Sat Jan 16, 2021 8:44 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: pKA, pKB, KA, KB
- Replies: 7
- Views: 340
Re: pKA, pKB, KA, KB
In the same way that a high pKa indicates a strong acid, the same goes for a high pKb and strong bases. A large pK indicated that products are high. Therefore, when bases are highly disassociated (strong base) there is a large product concentration.
- Sat Jan 16, 2021 8:40 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE Box
- Replies: 28
- Views: 1114
Re: ICE Box
Hey! The ICE box is only used for weak acids and bases.This is because they don't fully dissociate in water.
Strong acids and bases, on the other hand, completely ionize. Thus, we can just use the pH, Ka, or Kb formula. With strong acids and bases an ICE box is not necessary given their behavior.
Strong acids and bases, on the other hand, completely ionize. Thus, we can just use the pH, Ka, or Kb formula. With strong acids and bases an ICE box is not necessary given their behavior.
- Sun Jan 10, 2021 9:56 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Concentrations
- Replies: 9
- Views: 431
Re: Concentrations
Products and reactants are typically given. Sometimes when the initial of products is given, an ICE table can be used to find the final concentration of products and reactants and equilibrium.
- Sun Jan 10, 2021 9:54 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K vs P
- Replies: 6
- Views: 346
Re: K vs P
Kc is the equilibrium quotient which takes into account concentration. Kp is the equilibrium quotient which takes into account pressure. Given partial pressures, concentration can be solved using PV=nRT.
- Sun Jan 10, 2021 9:49 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Substances for Calculating K
- Replies: 4
- Views: 100
Re: Substances for Calculating K
Solids and liquids have little change to no in heterogenous reactions, so we just do not take them into account when calculating K because of their small participation in equilibrium
- Sun Jan 10, 2021 9:47 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Q and K
- Replies: 8
- Views: 354
Re: Q and K
Q is the reaction quotient. That is, the concentration of the products over the reactants. K is a reaction quotient where the values are at equilibrium. Q is subject to change for a reaction as the amounts of products and reactants can change. However, Q will eventually = K, as reactions eventually ...
- Sun Jan 10, 2021 9:42 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Using "ICE"
- Replies: 9
- Views: 388
Re: Using "ICE"
If the given information is kp, then the rice table would use partial pressure. If the given information is kc, then molarity/concentration would be used.
- Thu Dec 10, 2020 5:20 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Affect of pH on enzymes
- Replies: 2
- Views: 175
Affect of pH on enzymes
Although this topic is not covered in the exams, I was just trying to understand conceptually how extreme pH denatures enzymes. I understand the critical importance of pH in biological systems, but what is taking place from a chemistry standpoint when an enzyme is in an extremely acidic or extremely...
- Thu Dec 10, 2020 5:16 pm
- Forum: Dipole Moments
- Topic: Dipole arrows
- Replies: 9
- Views: 649
Re: Dipole arrows
Dipole arrows show where the electrons have a high propensity to lie. They typically point to the most electronegative atom in the molecule. For example, in H2O the dipole arrows would point toward the oxygen atom.
- Thu Dec 10, 2020 5:14 pm
- Forum: Bronsted Acids & Bases
- Topic: Identifying Strong Acids and Bases
- Replies: 7
- Views: 422
Re: Identifying Strong Acids and Bases
Table J.1 on page F77 in the textbook provides a table for commons strong acids and bases. I found memorizing these were extremely helpful! However, remembering that large bond lengths and highly EN anions also make strong acids is also helpful to remember conceptually.
- Thu Dec 10, 2020 5:07 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: Concept of pH
- Replies: 10
- Views: 531
Re: Concept of pH
At least biologically speaking, pH really matters for various systems. For example, we NEED strong acids in our digestive system to break down food, otherwise we'd not be able to extract nutrients as efficiently. However, enzymes denature in acids, therefore our bodies produce the sodium bicarbonat...
- Thu Dec 10, 2020 5:04 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: Concept of pH
- Replies: 10
- Views: 531
Re: Concept of pH
At least biologically speaking, pH really matters for various systems. For example, we NEED strong acids in our digestive system to break down food, otherwise we'd not be able to extract nutrients as efficiently. However, enzymes denature in acids, therefore our bodies produce the sodium bicarbonat...
- Sun Dec 06, 2020 4:02 pm
- Forum: Electronegativity
- Topic: What determine bond strength?
- Replies: 5
- Views: 492
Re: What determine bond strength?
Yes, you're completely correct in that size contributes a lot to how strong a bond is. Larger radii means larger distance between nuclei, which creates a bond that is easier to break. Also, bond order is extremely important in determining bond strength. Triple bonds are a lot stronger than double b...
- Sun Dec 06, 2020 4:01 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: Salts cause acidity
- Replies: 5
- Views: 372
Re: Salts cause acidity
The ions Na+ and Cl− are spectator ions and don't react with water. So, the pH doesn't change. A spectator ion is an ion that exists as a reactant and a product in a chemical equation.
- Sun Dec 06, 2020 3:58 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: Bronsted Acids vs Lewis Acids
- Replies: 4
- Views: 321
Re: Bronsted Acids vs Lewis Acids
All Bronsted-Lowry acids are Lewis acids, but the reverse is not true. Every Bronsted-Lowry base is also a Lewis base, but the reverse is not true.
A Lewis acid is anything that accepts a pair of electrons, while a Bronsted acid accepts pairs of electrons at an acidic hydrogen
A Lewis acid is anything that accepts a pair of electrons, while a Bronsted acid accepts pairs of electrons at an acidic hydrogen
- Sun Dec 06, 2020 3:55 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: Concept of pH
- Replies: 10
- Views: 531
Concept of pH
I understand how to solve for pH. But I am having a hard time conceptualizing the significance of the presence of protons (H+) in solutions? Why is knowledge of pH important and what makes a highly acidic/basic solution special?
- Sun Dec 06, 2020 3:52 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: Midterm 3C
- Replies: 9
- Views: 779
Re: Midterm 3C
NH4Cl is a salt. When it dissolves, the NH4+ ions in water can donate a proton. This ability to donate protons lowers the pH.
- Sat Nov 28, 2020 12:10 pm
- Forum: Sigma & Pi Bonds
- Topic: Carbon bonds
- Replies: 4
- Views: 235
Re: Carbon bonds
The carbon usually forms 4 bonds because it wants to fill up it's 4 orbitals (2sp3) to be stable. There are many reasons why carbon can be called "special" - it can form huge chains of carbon that can form macromolecules which are big enough for larger organism to use. - it is very stable...
- Sat Nov 28, 2020 12:09 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: H2O VSEPR
- Replies: 27
- Views: 1177
Re: H2O VSEPR
Becase H2O has 2 lone pairs, it has a AX2E generic formula. This is a bent shape. Remember that A is the central Atom, X is the # of bonded atoms, and E is the # of lone pairs This chart is very helpful in recognizing the shapes: https://www.templateroller.com/template/86292/vsepr-theory-molecular-s...
- Sat Nov 28, 2020 12:04 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Which shapes to memorize
- Replies: 11
- Views: 707
Re: Which shapes to memorize
I studies the shapes that he shared on lecture and tried my best to understand them conceptually so that I could understand them:Trigonal Planar, tetrahedral, trigonal bipyramidal, octahedral, trigonal pyramidal, see-saw, square planar. Once I recognized the pattern in the repulsions, it helped me m...
- Thu Nov 26, 2020 1:58 pm
- Forum: Trends in The Periodic Table
- Topic: atomic radius of anions
- Replies: 9
- Views: 465
Re: atomic radius of anions
In neutral state, Bromine is smaller than Na due to it's location on the far right of the periodic table. However, Br- is an anion. Anions have bigger ionic radii than their corresponding neutral atoms.
- Thu Nov 26, 2020 1:48 pm
- Forum: Properties of Light
- Topic: Momentum of light
- Replies: 6
- Views: 359
Re: Momentum of light
Correct, photons do not have mass but they still have a momentum which allows it to carry Energy. An object can have momentum without mas if it is a wave. A wave transports momentum via its waving motion and not by physically transporting an object with mass.
- Thu Nov 26, 2020 1:42 pm
- Forum: Sigma & Pi Bonds
- Topic: Carbon bonds
- Replies: 4
- Views: 235
Carbon bonds
If Carbon only has 2 unpaired electrons, why does it form 4 bonds?
How does this ability to form 4 bonds make organic molecules so special?
How does this ability to form 4 bonds make organic molecules so special?
- Thu Nov 26, 2020 1:38 pm
- Forum: Electronegativity
- Topic: Periodic Table Trend
- Replies: 40
- Views: 2109
Re: Periodic Table Trend
Ionization energy and electronegativity decrease down a group. Ionization energy and electronegativity also increase across a period. What helps me remember this is to remember that fluorine is the smallest and most electronegative atom, if you look at the periodic table you will see that it is at t...
- Thu Nov 26, 2020 1:36 pm
- Forum: Electronegativity
- Topic: What determine bond strength?
- Replies: 5
- Views: 492
What determine bond strength?
In determining bond strength, which characteristic take priority? Is it size of atom (and thus bond length) or electronegativity of an atom in a molecule? CF4 has a very strong bond because of the small size of the fluorine atom and the short bond lengths. The textbook also says, "note that ele...
- Thu Nov 26, 2020 1:33 pm
- Forum: Electronegativity
- Topic: Electronegativity and Bond Strength
- Replies: 4
- Views: 3636
Re: Electronegativity and Bond Strength
To elaborate on the statement "note that electronegativity and polarity arguments would predict the C--F bond to be the weakest", because Fluorine is highly electronegative, then the bond is weak because F is strongly attracting the electron which belong to Carbon. Thus it would be easier ...
- Thu Nov 26, 2020 1:25 pm
- Forum: Electronegativity
- Topic: Partial vs Formal charge
- Replies: 8
- Views: 903
Re: Partial vs Formal charge
The formal charge of an atom indicates the gain or loss of an electron while forming a covalent bond. To determine the formal charge I use the following rationale: Formal Charge = Valence electrons of neutral atom - (Shared electrons/2 - lone pair electrons)
- Thu Nov 26, 2020 12:56 pm
- Forum: Electronegativity
- Topic: Polarity of Molecules
- Replies: 10
- Views: 535
Re: Polarity of Molecules
When looking at the lewis structure, polarity can be determined from the symmetry of the lewis structure. The more symmetrical the appearance of the lewis structure is, the more likely it is to be polar. Also, knowing the electronegativity of each element (from the trends) is a consistent reliable w...
- Mon Nov 16, 2020 5:15 pm
- Forum: Electronegativity
- Topic: Partial vs Formal charge
- Replies: 8
- Views: 903
Re: Partial vs Formal charge
The formal charge is the charge that an atom appears to have when we count the electrons according to certain arbitrary rules. Formal charge is an integer property that is essential for the correct valence representation of a molecule.
The partial charge is the charge that the atom really has.
The partial charge is the charge that the atom really has.
- Mon Nov 16, 2020 5:12 pm
- Forum: Electronegativity
- Topic: Tips on remembering trend
- Replies: 5
- Views: 286
Re: Tips on remembering trend
I remember that helium is the smallest atom and that francium is the largest. Because there are added shells with each descending row, I know that as I go down, atoms get larger. Also, I know that noble gases are the most stable elements and thus they are more tightly held..thus I remember that as I...
- Mon Nov 16, 2020 5:06 pm
- Forum: Electronegativity
- Topic: Relationship between Dispersion and Electronegativity
- Replies: 6
- Views: 352
Re: Relationship between Dispersion and Electronegativity
Electronegativity determines the intramolecular forces (the forces that hold atoms in place). Electronegativity will determine whether the molecule is polar or non-polar, in other words, the chemical bond. The intramolecular forces affect the nature of the INTERmolecular forces (forces that hold mol...
- Mon Nov 16, 2020 4:55 pm
- Forum: Electronegativity
- Topic: polar vs nonpolar
- Replies: 26
- Views: 981
Re: polar vs nonpolar
The difference in electronegativity needs to be between 0.5 and 1.6 to be considered polar!
- Mon Nov 16, 2020 4:53 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Oxidation Sapling 9
- Replies: 6
- Views: 389
Re: Oxidation Sapling 9
Sum of oxidation numbers for a neutral compound is always 0. Sum of oxidation numbers for a polyatomic ion is the ion charge. When calculating oxidation numbers, remember that group 1A elements are always +1, Group 2A are always +2, Halogens are usually -1 (positive with oxygen). Hydrogen is always ...
- Sun Nov 08, 2020 12:30 pm
- Forum: Properties of Electrons
- Topic: Understanding energy transitions
- Replies: 4
- Views: 191
Re: Understanding energy transitions
When the energy is higher, the wavelength is shorter. This relationship can be observed from the energy equation. n=6 to n=1 has a greater energy emission than n=6 to n=5, therefore the wavelength would be shorter.
- Sun Nov 08, 2020 12:28 pm
- Forum: Properties of Electrons
- Topic: Electrons as Waves and Particles
- Replies: 4
- Views: 185
Re: Electrons as Waves and Particles
All electrons behave wave-like and particle-like. Larger objects are not affected by waves because they are so massive, and they are also more predictable than small objects. These principles are derived from the Heisenberg Uncertainty Principle.
- Sun Nov 08, 2020 12:19 pm
- Forum: Properties of Electrons
- Topic: intensity vs energy
- Replies: 29
- Views: 3114
Re: intensity vs energy
The intensity of light is dependent on the amount of photons. However the intensity does not determine on the overall energy.
The photoelectric effect shows that frquency has effect on the ejection of electrons.
The photoelectric effect shows that frquency has effect on the ejection of electrons.
- Sun Nov 08, 2020 12:15 pm
- Forum: Properties of Electrons
- Topic: Energy needed to remove an electron
- Replies: 3
- Views: 158
Re: Energy needed to remove an electron
I conceptualize it using this equation: https://www.google.com/imgres?imgurl=https%3A%2F%2Fslideplayer.com%2Fslide%2F3866354%2F13%2Fimages%2F8%2FThe%2Bphotoelectric%2Bequation.jpg&imgrefurl=https%3A%2F%2Fslideplayer.com%2Fslide%2F3866354%2F&tbnid=YQrn8DIi441WVM&vet=12ahUKEwijxoaQ4fPsAhVh...
- Sun Nov 08, 2020 12:10 pm
- Forum: Properties of Electrons
- Topic: Electron Spin
- Replies: 7
- Views: 439
Re: Electron Spin
Technically, electrons have an angular momentul which is a type of momentum possessed by rotating objects. This attributes the spinning nature and it is is a fundamental characteristic of electrons.
- Sun Nov 08, 2020 12:08 pm
- Forum: Ionic & Covalent Bonds
- Topic: Resonance and Bond Order
- Replies: 2
- Views: 115
Re: Resonance and Bond Order
Bond length is defined as the distance between the centers of two covalently bonded atoms. The length of the bond is determined by the number of bonded electrons (the bond order). The higher the bond order, the stronger the pull between the two atoms and the shorter the bond length.
- Sun Nov 08, 2020 12:05 pm
- Forum: Ionic & Covalent Bonds
- Topic: Electronegativity
- Replies: 16
- Views: 906
Re: Electronegativity
Fluorine is the most electronegative element because it has 5 electrons in it's 2P shell. Because it only requires 1 electron to reach stability, it is highly reactive.
- Sun Nov 08, 2020 12:03 pm
- Forum: Ionic & Covalent Bonds
- Topic: Extra Valence Electrons
- Replies: 10
- Views: 403
Re: Extra Valence Electrons
Those elements are just exceptions to the octet rule.
- Sun Nov 08, 2020 11:57 am
- Forum: Ionic & Covalent Bonds
- Topic: Electron Affinity vs. Electronegativity
- Replies: 12
- Views: 1288
Re: Electron Affinity vs. Electronegativity
Electronegativity is the ability of an atom to attract electrons from outside, it is a qualitative property, measured from Pauling units, and it's applied for a single atom. Electron affinity is the amount of energy released when a neutral atom or molecule gains an electron from outside, it is a qua...
- Sun Nov 08, 2020 11:50 am
- Forum: Properties of Light
- Topic: rydberg's constant
- Replies: 11
- Views: 841
Re: rydberg's constant
It depends on which equation is being used.
R = 3.28984 x10^15 Hz is used for the Rydberg equation with frequency, or v = R(1/n1^2 - 1/n2^2).
R = 1.097x10^7 m is used for the Rydberg equation with wavelength, or 1/wavelength = R(1/n1^2 - 1/n2^2).
R = 3.28984 x10^15 Hz is used for the Rydberg equation with frequency, or v = R(1/n1^2 - 1/n2^2).
R = 1.097x10^7 m is used for the Rydberg equation with wavelength, or 1/wavelength = R(1/n1^2 - 1/n2^2).
- Sun Nov 08, 2020 11:48 am
- Forum: Properties of Light
- Topic: Equation clarifications
- Replies: 4
- Views: 228
Re: Equation clarifications
The equation is actually E=hc/λ where λ is wavelength.
However we can extract the equation c/λ = v where v is frequency and c is the speed of light.
However we can extract the equation c/λ = v where v is frequency and c is the speed of light.
- Sun Nov 08, 2020 11:38 am
- Forum: Properties of Light
- Topic: Which model of light is atomic spectroscopy?
- Replies: 8
- Views: 461
Re: Which model of light is atomic spectroscopy?
The particle model is used for atomic spectroscopy
- Sun Nov 08, 2020 11:32 am
- Forum: Properties of Light
- Topic: Midterm Question
- Replies: 11
- Views: 528
Re: Midterm Question
The fundamentals until 1D. These topics are on the chemistry website.
- Sun Nov 08, 2020 11:31 am
- Forum: Properties of Light
- Topic: Is c always the speed of light?
- Replies: 92
- Views: 4742
Re: Is c always the speed of light?
In this class, you can always count on c being the speed of light.
- Sun Nov 08, 2020 11:30 am
- Forum: Properties of Light
- Topic: How to remember what v is in equations
- Replies: 46
- Views: 6842
Re: How to remember what v is in equations
Typically nu denotes frequency, which looks like an italicized v. A diligent way to confirm whether or not it is velocity or frequency is to check the units! Velocity is in m/s whereas frequency is in Hz. Typically the speed of light is denoted with "c"
- Sun Nov 08, 2020 11:28 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Subshell Definition
- Replies: 9
- Views: 366
Re: Subshell Definition
This infograpgic was helpul to me when differentiating the terms: https://pediaa.com/wp-content/uploads/2 ... ummary.png
- Sun Nov 08, 2020 11:25 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Orbital energy
- Replies: 5
- Views: 308
Re: Orbital energy
4s orbitals are said to have a lower energy than the 3d orbitals because they are filled first.
- Sun Nov 08, 2020 11:22 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Orbital vs Subshell
- Replies: 7
- Views: 461
Re: Orbital vs Subshell
Shells are composed of electrons that share the same principal quantum number. Whereas subshells are composed of electrons that share the same angular momentum quantum number whereas orbitals are composed of electrons that are in the same energy level but have different spins. This infographic helps...
- Sun Nov 08, 2020 11:19 am
- Forum: Administrative Questions and Class Announcements
- Topic: Advice from a Medical Student [ENDORSED]
- Replies: 297
- Views: 374247
Re: Advice from a Medical Student [ENDORSED]
Thanks so much for your advice! I will definitely keep my notes handy as I go through my UCLA journey. Can you tell us a little bit more about your gap year? What types of clubs/ internships/ research opportunities/ etc. you were involved in that helped strengthen your medical school application? M...
- Sun Oct 11, 2020 11:13 am
- Forum: Administrative Questions and Class Announcements
- Topic: Advice from a Medical Student - Part II [ENDORSED]
- Replies: 298
- Views: 241143
Re: Advice from a Medical Student - Part II [ENDORSED]
Thank you so much for dedicating time to writing this. It was so incredibly helpful to me.
- Sun Oct 11, 2020 11:09 am
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Calculating number of moles of an element
- Replies: 10
- Views: 361
Re: Calculating number of moles of an element
100g is a tool to help conceptualize the elemental proportions of a molecule to equal 100%. It's an arbitrary number that always works in those problems.
- Sun Oct 11, 2020 11:07 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2762980
Re: Post All Chemistry Jokes Here
Why do chemists like nitrates so much?
They're cheaper than day rates.
I asked the guy sitting next to me if he had any Sodium Hypobromite…
He said NaBrO
They're cheaper than day rates.
I asked the guy sitting next to me if he had any Sodium Hypobromite…
He said NaBrO
- Sun Oct 11, 2020 11:04 am
- Forum: Student Social/Study Group
- Topic: Final Jitters
- Replies: 457
- Views: 329216
Re: Final Jitters
I allocate a set time to review my notes and perhaps for practice problems, but not too much time at once. If I overspend my time all at once for studying I am overwhelmed. So, maybe 30 min of skimming over my notes, and then 20 minutes doing some problems. That is one session. Then, I take breaks t...
- Sun Oct 11, 2020 10:59 am
- Forum: Molarity, Solutions, Dilutions
- Topic: Formulas involved in Determining Solution Concentration
- Replies: 8
- Views: 697
Re: Formulas involved in Determining Solution Concentration
When completing problems on solutions, I am not quick to apply the formulas in which you described (M=n/v or M Initial V final = M final V final) When it comes to solutions concentrations, it helps to internalize and conceptualize the principles used to create those formulas. When diluting a solutio...