Search found 106 matches

by Victor Qiu 1C
Sun Feb 28, 2021 8:24 am
Forum: Ideal Gases
Topic: K and Q
Replies: 16
Views: 424

Re: K and Q

K=Q only when the reaction is at equilibrium. K is the constant at equilibrium, while Q can be the constant at any time. I think this website can help: https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/E...
by Victor Qiu 1C
Sun Feb 28, 2021 8:17 am
Forum: Ideal Gases
Topic: gas constant R
Replies: 5
Views: 660

Re: gas constant R

Yes, it depends on the units.

There are 4 values that are used more often:
R = 0.0821 L·atm/(mol·K) = 8.3145 J/(mol·K) = 8.2057 m3·atm/(mol·K) = 62.3637 L·Torr/(mol·K)
by Victor Qiu 1C
Sun Feb 28, 2021 8:14 am
Forum: Ideal Gases
Topic: The difference: ideal gas, ideal condition, ideal behavior
Replies: 3
Views: 440

Re: The difference: ideal gas, ideal condition, ideal behavior

I think there are several characteristics that are assumed for ideal gas: (1) the collisions between gas molecules are elastic and conservation of energy occurs among the molecules; (2) the total volume of the individual molecules is negligible comparing with the volume the gas occupies; (3) no inte...
by Victor Qiu 1C
Sun Feb 28, 2021 8:05 am
Forum: Balancing Redox Reactions
Topic: Monoatomic Ions
Replies: 2
Views: 20

Re: Monoatomic Ions

Because it is ClO4- in KClO4 but it is Cl- in KCl.
by Victor Qiu 1C
Sun Feb 28, 2021 8:01 am
Forum: Balancing Redox Reactions
Topic: oxidation states for final?
Replies: 13
Views: 43

Re: oxidation states for final?

For group 1 elements, the oxidation state is always +1. For group 2 elements, the oxidation state is always +2. Oxygen is usually -2, except in examples like H 2 O 2 and F 2 O. I think you can find more information on this website: https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplem...
by Victor Qiu 1C
Sun Feb 28, 2021 7:47 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Diamond vs. Graphite
Replies: 16
Views: 49

Re: Diamond vs. Graphite

Yes, the activation energy is very high, so it would take very long for diamond to become graphite. There is more information about this on this website:
https://chemistry.stackexchange.com/questions/34193/are-diamonds-really-forever
by Victor Qiu 1C
Sun Feb 28, 2021 7:40 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: E° vs. E and G° vs. G
Replies: 12
Views: 30

Re: E° vs. E and G° vs. G

Yes. I think most of data are collected at STP, which is at 101.325kPa (1atm) and 0°C (273.15K), and when we try to calculate E or G at different temperatures or pressures, we can use the compare them with the E° and G° to get the answer.
by Victor Qiu 1C
Thu Feb 25, 2021 12:03 pm
Forum: Ideal Gases
Topic: Pascal and Bar
Replies: 2
Views: 483

Re: Pascal and Bar

I think the values are:

1 atm = 101325 Pa = 101.325 kPa = 1.013 bar = 760 torr
by Victor Qiu 1C
Thu Feb 25, 2021 11:59 am
Forum: Ideal Gases
Topic: STP
Replies: 12
Views: 222

Re: STP

I think the values are:
Standard Temperature and Pressure (STP): 101.325kPa (1atm), 0°C (273.15K);
Standard Ambient Temperature and Pressure (STP): 101.325kPa (1atm), 25°C (298.15K).
by Victor Qiu 1C
Thu Feb 25, 2021 11:56 am
Forum: Ideal Gases
Topic: 4.17 How to Identify When We Should Use the Ideal Gas Law?
Replies: 4
Views: 30

Re: 4.17 How to Identify When We Should Use the Ideal Gas Law?

I think if you are dealing with a chemistry problem, you can assume that the gas is an idea gas, and you can apply ideal gas law for most of the times. Nevertheless, the real characteristics of ideal gas should include: (1) the collisions between gas molecules are elastic and conservation of energy ...
by Victor Qiu 1C
Thu Feb 25, 2021 10:49 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta G v Delta G Naught
Replies: 9
Views: 27

Re: Delta G v Delta G Naught

You can still use the equation ΔG = ΔG + RTlnQ to derive.
by Victor Qiu 1C
Thu Feb 25, 2021 10:36 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Combustion and Spontaneity [ENDORSED]
Replies: 3
Views: 55

Re: Combustion and Spontaneity [ENDORSED]

I think because combustion usually releases lots of heat, which means ΔH<0, and the reaction is very exothermic, ΔG would very likely be G<0.
by Victor Qiu 1C
Thu Feb 25, 2021 10:31 am
Forum: Phase Changes & Related Calculations
Topic: Endothermic v. Exothermic
Replies: 105
Views: 325

Re: Endothermic v. Exothermic

ΔH<0, exothermic, releases heat;
ΔH>0, endothermic, absorbs heat;
ΔG<0, exergonic, spontaneous;
ΔG>0, endergonic, not spontaneous.
by Victor Qiu 1C
Thu Feb 25, 2021 10:17 am
Forum: Ideal Gases
Topic: Bars to atm [ENDORSED]
Replies: 41
Views: 241

Re: Bars to atm [ENDORSED]

1 atm = 101325 Pa = 101.325 kPa = 1.013 bar = 760 torr
by Victor Qiu 1C
Thu Feb 25, 2021 9:58 am
Forum: Van't Hoff Equation
Topic: How deltaG affects product/reactant formation
Replies: 6
Views: 26

Re: How deltaG affects product/reactant formation

It is not true that if there are more products than reactants, the formation of reactants would be favored. You can just think of an example of dissociation of a strong acid.
HCl(aq) + H2O(l) → H3O+(aq) + Cl-(aq)
The products are favored even when there are more products than reactants.
by Victor Qiu 1C
Sun Feb 21, 2021 8:18 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: degeneracy and entropy
Replies: 5
Views: 20

Re: degeneracy and entropy

Kb = 1.38065 × 10−23J/K
by Victor Qiu 1C
Sun Feb 21, 2021 8:14 am
Forum: Ideal Gases
Topic: Ideal Gas vs/ Real Gas
Replies: 10
Views: 34

Re: Ideal Gas vs/ Real Gas

There are several characteristics that are assumed for ideal gas: (1) the collisions between gas molecules are elastic and conservation of energy occurs among the molecules; (2) the total volume of the individual molecules is negligible comparing with the volume the gas occupies; (3) no intermolecul...
by Victor Qiu 1C
Sun Feb 21, 2021 8:10 am
Forum: Biological Examples (*DNA Structural Transitions, etc.)
Topic: STP [ENDORSED]
Replies: 8
Views: 720

Re: STP [ENDORSED]

Standard Temperature and Pressure (STP): 101.325kPa (1atm), 0°C (273.15K);
Standard Ambient Temperature and Pressure (STP): 101.325kPa (1atm), 25°C (298.15K).
by Victor Qiu 1C
Sun Feb 21, 2021 7:50 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Equilibrium Systems
Replies: 7
Views: 42

Re: Equilibrium Systems

You can just treat other variables as constants to do the integral.
by Victor Qiu 1C
Fri Feb 19, 2021 3:17 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Find Enthalpy: 2HCl (aq) + Zn (s) --> H2(g)+ ZnCl2 (aq)
Replies: 3
Views: 5272

Re: Find Enthalpy: 2HCl (aq) + Zn (s) --> H2(g)+ ZnCl2 (aq)

I think the equation is not correct. I think you should use
ΔHfo(Zn2+)+2ΔHfo(Cl-)-2ΔHfo(HCl)
which gives
-153.89 kJ/mol + 2 × (-167.16 kJ/mol) - 2 × (-167.16 kJ/mol)
and the result is
ΔHr = -153.89 kJ/mol
by Victor Qiu 1C
Sun Feb 14, 2021 10:48 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Biological examples (ATP hydrolysis and osmotic pressure)
Replies: 5
Views: 48

Re: Biological examples (ATP hydrolysis and osmotic pressure)

ATP → ADP + Pi
ATP: adenosine triphosphate
ADP: adenosine diphosphate
Pi: phosphate ion
This reaction releases energy.
by Victor Qiu 1C
Sun Feb 14, 2021 10:37 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Temperature Question
Replies: 8
Views: 20

Re: Temperature Question

0K = -273.15°C
This, if we are considering a change in temperature (ΔT), 80 units in °C equal to 80 units in K.
by Victor Qiu 1C
Sun Feb 14, 2021 10:31 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: delta G
Replies: 9
Views: 33

Re: delta G

ΔG is free energy at a moment, while ΔGo is standard-state free energy.
ΔG = ΔGo + RTlnQ
by Victor Qiu 1C
Sun Feb 14, 2021 10:28 am
Forum: Ideal Gases
Topic: Ideal Gas
Replies: 3
Views: 32

Re: Ideal Gas

There are several characteristics of ideal gases: (1) the collisions between gas molecules are elastic and conservation of energy occurs among the molecules; (2) the total volume of the individual molecules is negligible comparing with the volume the gas occupies; (3) no intermolecular forces exist ...
by Victor Qiu 1C
Sun Feb 14, 2021 10:21 am
Forum: Ideal Gases
Topic: R ideal gas constant
Replies: 25
Views: 65

Re: R ideal gas constant

It depends on the units in the problem. I think we should use the value of R whose units are the same as the units in the problem.

There are 4 values that are used more often:
R = 0.0821 L·atm/(mol·K) = 8.3145 J/(mol·K) = 8.2057 m3·atm/(mol·K) = 62.3637 L·Torr/(mol·K)
by Victor Qiu 1C
Sun Feb 07, 2021 6:35 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Strong acids/bases
Replies: 10
Views: 82

Re: Strong acids/bases

Strong Acids: HCl, HBr, HI, (3 halogens)
HClO3, HClO4, (2 HClOn)
HNO3, H2SO4 (appears in problems very often)
Strong Bases: Group 1 hydroxides, Ca(OH)2, Sr(OH)2, Ba(OH)2, Group 1 and 2 oxides
by Victor Qiu 1C
Sun Feb 07, 2021 6:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ka2 << Ka1
Replies: 12
Views: 73

Re: Ka2 << Ka1

Take H3PO4 as an example, Ka1=7.1 × 10-3, Ka2=6.3 × 10-8, Ka3=4.5 × 10-13. The difference between Ka1 and Ka2 is at the scale of 105. Thus, in these cases, the second deprotonation can often be ignored.
by Victor Qiu 1C
Sun Feb 07, 2021 6:25 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pka vs ka
Replies: 18
Views: 56

Re: pka vs ka

log10(ab) = log10(a) + log10(b) is correct

Also,
if pKw = pKa + pKb
10-pKw = 10-(pKa+pKb)
10-pKw = 10-(pKa) × 10-(pKb)
Kw = Ka × Kb
by Victor Qiu 1C
Sun Feb 07, 2021 6:15 pm
Forum: Ideal Gases
Topic: Gas Constant Value
Replies: 43
Views: 133

Re: Gas Constant Value

I think there are 4 values that are used more often:
R = 0.0821 L·atm/(mol·K) = 8.3145 J/(mol·K) = 8.2057 m3·atm/(mol·K) = 62.3637 L·Torr/(mol·K)
by Victor Qiu 1C
Sun Feb 07, 2021 6:13 pm
Forum: Ideal Gases
Topic: Units for K
Replies: 29
Views: 105

Re: Units for K

I don’t think the units can cancel out all the time.
If A(aq) + B(aq) → 2C(aq) + D(aq)
Kc = [C]2 [D] / ([A] [B])
Because there is a square, one unit of [C] would not cancel out, and the unit of Kc should be the unit of [C].
by Victor Qiu 1C
Sun Jan 31, 2021 9:22 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Reverse direction (sapling q.5)
Replies: 7
Views: 60

Re: Reverse direction (sapling q.5)

ΔHforward=-ΔHreverse
Thus, if you are given the ΔH for forward reaction and you wish to use the ΔH for reverse reaction, you should add a negative sign to the value.
by Victor Qiu 1C
Sun Jan 31, 2021 9:17 pm
Forum: Ideal Gases
Topic: Kp?
Replies: 30
Views: 118

Re: Kp?

Yes, partial pressure only applies to gases. Just imagine adding a solid, a liquid, and a gas into a closed box. The solid and liquid would just occupy some volume of that box, but the gas would occupied the entire volume of that box. Therefore, only the gas would have partial pressure.
by Victor Qiu 1C
Sun Jan 31, 2021 9:12 pm
Forum: Calculating Work of Expansion
Topic: Gas Constant
Replies: 13
Views: 324

Re: Gas Constant

It depends on the units you are using.
R = 0.0821 L·atm/(mol·K) = 8.3145 J/(mol·K) = 8.2057 m3·atm/(mol·K) = 62.3637 L·Torr/(mol·K)
by Victor Qiu 1C
Sun Jan 31, 2021 9:06 pm
Forum: Calculating Work of Expansion
Topic: Extensive vs Intensive
Replies: 4
Views: 318

Re: Extensive vs Intensive

To give an example, heat capacity is an extensive property, while specific heat capacity is an intensive property. Heat capacity is the amount of heat given to a material with certain mass to make 1°C change in its temperature, while specific heat capacity is amount of heat needed to add to 1g of th...
by Victor Qiu 1C
Sun Jan 31, 2021 8:57 pm
Forum: Calculating Work of Expansion
Topic: Which R to use?
Replies: 4
Views: 286

Re: Which R to use?

R = 0.0821 L·atm/(mol·K)
by Victor Qiu 1C
Sun Jan 31, 2021 8:52 pm
Forum: Calculating Work of Expansion
Topic: Energy and the System/Surroundings
Replies: 8
Views: 35

Re: Energy and the System/Surroundings

Hello! I think posts above have already explained the first question very well, and I would just add a little bit information on the second question. The first law of thermodynamics states that energy cannot be destroyed or created (conservation of energy). Thus, it is very reasonable to think that ...
by Victor Qiu 1C
Sun Jan 24, 2021 7:35 am
Forum: Ideal Gases
Topic: Ideal Gas Law as an Approximation
Replies: 3
Views: 122

Re: Ideal Gas Law as an Approximation

I think that means that we can easily see if we can apply PV=nRT in the question.
by Victor Qiu 1C
Sun Jan 24, 2021 7:31 am
Forum: Ideal Gases
Topic: How Plausible is Ideal Gas?
Replies: 2
Views: 34

Re: How Plausible is Ideal Gas?

If the environment has higher temperature and lower pressure, the gas would act more ideal.
by Victor Qiu 1C
Sun Jan 24, 2021 7:18 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Ionization Constant of water
Replies: 4
Views: 34

Re: Ionization Constant of water

Kw=1×10-14, so that pKw=14=pH+pOH at 25°C.
by Victor Qiu 1C
Sun Jan 24, 2021 7:13 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Difference between Strong and Weak acids and bases
Replies: 3
Views: 16

Re: Difference between Strong and Weak acids and bases

Strong acids and bases would dissociate fully in water, but weak acids and bases would only dissociate partially.
by Victor Qiu 1C
Sun Jan 24, 2021 7:10 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Direction of arrows
Replies: 11
Views: 40

Re: Direction of arrows

I think that means the equilibrium favors one direction very much. The reaction would favor where the arrow points very much.
by Victor Qiu 1C
Sun Jan 17, 2021 9:13 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook Section 6E
Replies: 1
Views: 11

Re: Textbook Section 6E

I think H2SO4 is an exception because its Ka2 = 1.0×10−2, which is close to other acids' Ka1, so it should not be ignored.
by Victor Qiu 1C
Sun Jan 17, 2021 8:58 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Diprotic Acids
Replies: 2
Views: 29

Re: Diprotic Acids

I think in most of the times, yes. This is because the second Ka is often much smaller than the first Ka. Take H 3 PO 4 as an example, K a1 =7.1 × 10 -3 , K a2 =6.3 × 10 -8 , K a3 =4.5 × 10 -13 . The difference between K a1 and K a2 is at the scale of 10 5 . Thus, I think the second Ka can often be ...
by Victor Qiu 1C
Sun Jan 17, 2021 8:53 am
Forum: Polyprotic Acids & Bases
Topic: Ignoring Second Deprotonation
Replies: 2
Views: 27

Re: Ignoring Second Deprotonation

Take H3PO4 as an example, Ka1=7.1 × 10-3, Ka2=6.3 × 10-8, Ka3=4.5 × 10-13. The difference between Ka1 and Ka2 is at the scale of 105. Thus, I think if it is not clarified specifically, the second deprotonation can often be ignored.
by Victor Qiu 1C
Sun Jan 17, 2021 8:42 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Converting Qc to Qp [ENDORSED]
Replies: 4
Views: 197

Re: Converting Qc to Qp [ENDORSED]

The way to calculate K c and Q c is very similar. Both are the relative ratio of products to reactants. The only difference is that K c is the relative ratio of products to reactants when the reaction is at equilibrium, while Q c is the relative ratio of products to reactants at a given instant (the...
by Victor Qiu 1C
Sun Jan 17, 2021 8:23 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Quotient
Replies: 12
Views: 450

Re: Quotient

Basically, K is the relative ratio of products to reactants when the reaction is at equilibrium, while Q is the relative ratio of products to reactants at a given instant (the reaction might not be at equilibrium).
by Victor Qiu 1C
Sun Jan 10, 2021 11:27 pm
Forum: Lewis Structures
Topic: Lewis Structure XeF_2
Replies: 4
Views: 318

Re: Lewis Structure XeF_2

Nan_Guan_1L wrote:I think you can still draw the structure horizontally it doesn't really matter. as long as you represent the bond angle is roughly 180 degree I think it works either way you draw it.

I don't think you need to consider the bond angle when drawing a lewis structure.
by Victor Qiu 1C
Sun Jan 10, 2021 8:16 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: atm
Replies: 2
Views: 398

Re: atm

I think just using same units in calculation would be fine. You can always convert units.
R=8.314 J mol-1 K-1=0.08205 L atm mol-1 K-1=62.363 mmHg L mol-1 K-1
by Victor Qiu 1C
Sun Jan 10, 2021 8:13 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Fall 2010, Question #6C (Equilibrium shifts right or left?)
Replies: 4
Views: 285

Re: Fall 2010, Question #6C (Equilibrium shifts right or left?)

According to the Le Chatelier's principle, the reaction would shift to counteract the change. Therefore, if more products are added, the reaction should shift towards the reactants because in this way, there will be less products and more reactants and the reaction counteracts the change of adding m...
by Victor Qiu 1C
Sun Jan 10, 2021 8:03 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Converting between K and Kc
Replies: 2
Views: 429

Re: Converting between K and Kc

The formula should be easy to derive using PV=nRT:
P=nRT/V, because n/V is concentration,
P=cRT,
and because when calculating equilibrium constants, the stoichiometric coefficients should be the exponents, so take that into consideration,
KP=(RT)ΔnKc, Δn=nProducts-nReactants
by Victor Qiu 1C
Sun Jan 10, 2021 7:58 am
Forum: Ideal Gases
Topic: Units for Pressure
Replies: 41
Views: 849

Re: Units for Pressure

I don't think the unit of pressure should must be in atm. I think just using same units in calculation would be fine.
R=8.314 J mol-1 K-1=0.08205 L atm mol-1 K-1=62.363 mmHg L mol-1 K-1
by Victor Qiu 1C
Sun Jan 10, 2021 7:50 am
Forum: Ideal Gases
Topic: P over R in the Ideal Gas Law
Replies: 4
Views: 19

Re: P over R in the Ideal Gas Law

I think you should clarify if the K is K c or K P . I think if you are referring to K c , you should not assume that P/R is directly proportional to K c because when calculating K c , the concentrations are the bases while the stoichiometric coefficients are the exponents. The stoichiometric coeffic...
by Victor Qiu 1C
Wed Dec 09, 2020 10:41 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: d-orbitals
Replies: 2
Views: 128

Re: d-orbitals

I think for d orbitals, there are dxy, dyz, dxz, dx2-y2, and dz2.
by Victor Qiu 1C
Wed Dec 09, 2020 10:29 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration for Bi3+
Replies: 2
Views: 923

Re: Electron Configuration for Bi3+

Because it should follow the order 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 5f 6d...
by Victor Qiu 1C
Wed Dec 09, 2020 10:24 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration of Scandium
Replies: 4
Views: 294

Re: Electron Configuration of Scandium

It should follow the order 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 5f 6d... However, I think [Ar] 3d14s2 and [Ar] 4s23d1 are the same, and it does matter whether 4s or 3d is written first. They both represent the electron configuration of Sc.
by Victor Qiu 1C
Wed Dec 09, 2020 10:17 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Valence-Shell Configurations
Replies: 2
Views: 473

Re: Valence-Shell Configurations

Valence shell configuration refers to the electrons in the outermost shell. The alkali earth metals are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra), and the respective electron configurations are [He] 2s 2 , [Ne] 3s 2 , [Ar] 4s 2 , [Kr] 5s 2 , [Xe] 6s 2...
by Victor Qiu 1C
Wed Dec 09, 2020 10:02 pm
Forum: Bronsted Acids & Bases
Topic: Fundamentals J.7 b)
Replies: 1
Views: 33

Re: Fundamentals J.7 b)

The electron configuration of Zn is [Ar] 3d10 4s2. Therefore, we can infer that Zn would likely to lose the 2 electrons in 4s2 and form Zn2+. Therefore, as 2+2×(-1)=0, we should write Zn(OH)2 because it's Zn2+ and 2OH-.
by Victor Qiu 1C
Sun Dec 06, 2020 8:29 pm
Forum: Naming
Topic: Cl & Br3
Replies: 7
Views: 62

Re: Cl & Br3

I think Br3- is tribromide, while Br- is bromide.
by Victor Qiu 1C
Sun Dec 06, 2020 8:23 pm
Forum: Lewis Structures
Topic: Lewis Structure of XeO3?
Replies: 2
Views: 8462

Re: Lewis Structure of XeO3?

I think Kevin Wright’s answer is correct. Just to add on it, Xe forms 3 double bonds with 3 O, respectively, and has a lone pair electrons. Also, each O has 2 pairs of lone pair electrons.
by Victor Qiu 1C
Sun Dec 06, 2020 8:06 pm
Forum: Lewis Structures
Topic: Lewis Structure for CH2
Replies: 4
Views: 4301

Re: Lewis Structure for CH2

I think its H — C: — H, and it’s called methylene.
by Victor Qiu 1C
Sun Dec 06, 2020 7:59 pm
Forum: Lewis Structures
Topic: Lewis Structure for CO
Replies: 3
Views: 469

Re: Lewis Structure for CO

C has 4 valences electrons, O has 6 valence electrons. If there is a double bond in CO, C still needs 2 pairs of lone pair electrons to satisfy octet rule, and O also needs 2 pairs of lone pair electrons to satisfy the octet rule. Therefore, in total there should be 2×2+2×2+2×2=12 electrons. However...
by Victor Qiu 1C
Sun Dec 06, 2020 7:51 pm
Forum: Lewis Structures
Topic: Valence Electrons
Replies: 5
Views: 332

Re: Valence Electrons

Valence electrons are the electrons in the outer shell. If we use element carbon as an example. Carbon has the electron configuration [He]2s22p2. We can see that its outer shell is n=2, which is 2s and 2p. Thus, its valence electrons are 2+2=4.
by Victor Qiu 1C
Sun Nov 29, 2020 5:15 am
Forum: Lewis Structures
Topic: Lewis Structure XeF_2
Replies: 4
Views: 318

Re: Lewis Structure XeF_2

I do not think there is a reason. When drawing the Lewis structure, the same bond can be drawn in various ways (the bond angle does not matter). I think this is because Lewis structure is 2-D while the molecule is 3-D, therefore, there has to be some kind of distortion when trying to reflect the rea...
by Victor Qiu 1C
Sun Nov 29, 2020 5:09 am
Forum: Lewis Structures
Topic: Molecular Shapes
Replies: 5
Views: 415

Re: Molecular Shapes

To add on NeelPatelLec4's answer, for seesaw, the bond angle between axial and axial is 180°, between equatorial and equatorial is 120°, and between axial and equatorial is 90°. For trigonal pyramidal, the bond angle should be less than 109.5° due to the repulsion from the lone pair electrons.
by Victor Qiu 1C
Sun Nov 29, 2020 5:04 am
Forum: Lewis Structures
Topic: Bond Angles
Replies: 2
Views: 446

Re: Bond Angles

For seesaw structure, the bond angle between axial and axial is 180°, between equatorial and equatorial is 120°, and between axial and equatorial is 90°. For square planar structure, the bond angles should be 90°. These are the bond angles in ideal situations.
by Victor Qiu 1C
Sun Nov 29, 2020 4:55 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 5
Views: 44

Re: Bond Angles

Generally, lone pair electrons would make the bond angle to be smaller, because the lone pair electrons would have a repulsion force. For example, in a water molecule, there are 2 pairs of lone pair electrons, which makes the bond angle H-O-H to become 104.5°.
by Victor Qiu 1C
Sun Nov 29, 2020 4:51 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bent Shape molecules
Replies: 7
Views: 79

Re: Bent Shape molecules

I think molecules that are AX2E1 or AX2E2 have a bent shape.
by Victor Qiu 1C
Sun Nov 22, 2020 9:19 am
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Theory
Replies: 5
Views: 56

Re: VSEPR Theory

Yes, that means valence shell electron pair repulsion theory. Thus VSEPR theory.
by Victor Qiu 1C
Sun Nov 22, 2020 8:42 am
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Model Memorization
Replies: 3
Views: 26

Re: VSEPR Model Memorization

Yes, the amount is determined, like for tetrahedral, there are always 4 atoms bonding to central atom and no lone pair electrons at central atom. However, I think it requires much work to memorize these. You can just draw the Lewis structure and determine the shape.
by Victor Qiu 1C
Sun Nov 22, 2020 8:31 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Number of Molecular Shapes
Replies: 6
Views: 71

Re: Number of Molecular Shapes

I think we also have square pyramidal, pentagonal bipyramidal, pentagonal pyramidal, and others.
by Victor Qiu 1C
Sun Nov 22, 2020 8:21 am
Forum: Lewis Structures
Topic: Lewis Structure for Glycine
Replies: 3
Views: 37

Re: Lewis Structure for Glycine

Glycine is an amino acid. Amino acid always has an amine group, a carboxyl group, and a side chain (R group). Also, There is an α carbon at the center that is connected to the amine group, the carboxyl group, and the side chain. I think if we know that glycine follows this structure, it would be pre...
by Victor Qiu 1C
Sun Nov 22, 2020 8:12 am
Forum: Lewis Acids & Bases
Topic: How do I calculate expanded valence electrons?
Replies: 3
Views: 46

Re: How do I calculate expanded valence electrons?

The Cl atom in the middle forms 2 single bonds, and it has 3 lone pair electrons. Thus, the answer should be 10 valence electrons.
by Victor Qiu 1C
Sun Nov 15, 2020 9:30 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Writing Electron Configurations
Replies: 9
Views: 81

Re: Writing Electron Configurations

I always use the order 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p 8s...
by Victor Qiu 1C
Sun Nov 15, 2020 9:16 am
Forum: Lewis Structures
Topic: Dispersion forces in CH₃ CHO
Replies: 2
Views: 39

Re: Dispersion forces in CH₃ CHO

Just as what is said in the Dr. lavelle's lecture, London Dispersion Force always exists because electrons always exist, and electrons always fluctuate.
by Victor Qiu 1C
Sun Nov 15, 2020 8:57 am
Forum: Coordinate Covalent Bonds
Topic: OH
Replies: 5
Views: 51

Re: OH

OH- is not radical, •OH is radical.
by Victor Qiu 1C
Sun Nov 15, 2020 12:58 am
Forum: Ionic & Covalent Bonds
Topic: A2.23 Textbook Problem
Replies: 3
Views: 31

Re: A2.23 Textbook Problem

We can consider how the element would lose or gain electrons in its outer shell. For example, Mg is [Ne] 3s2, so it has the tendency to lose 2 electrons, which makes Mg ion Mg2+, and Al is [Ne] 3s23p1, so it has the tendency to lose 3 electrons, which makes Al ion Al3+.
by Victor Qiu 1C
Sun Nov 15, 2020 12:46 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Outline 2 Orbital Question
Replies: 4
Views: 61

Re: Outline 2 Orbital Question

We can consider the angular momentum quantum number. Electrons in s-, p-, d-, and f- orbitals have the angular momentum quantum number l = 0, 1, 2, and 3.
by Victor Qiu 1C
Sun Nov 08, 2020 8:16 am
Forum: Trends in The Periodic Table
Topic: Understanding trends in the Periodic Table
Replies: 2
Views: 50

Re: Understanding trends in the Periodic Table

Yes, there is an easy method. You can simply distinguish the s-,p-, d-, and f- blocks by thinking about the graph. You can try to think like you want to cut the periodic table into rectangles. First you move He to the left to make a thin rectangle, making a 2×7 rectangle that represents s-block. The...
by Victor Qiu 1C
Sun Nov 08, 2020 8:01 am
Forum: Ionic & Covalent Bonds
Topic: Salts and molecules
Replies: 4
Views: 61

Re: Salts and molecules

I would say yes, but one thing to be noticed is that, for example, NaCl(s) is a salt, but when it is dissolved in water, I would not call it a salt, because in water there are Na+ and Cl-, I would just call them sodium ion and chloride ion.
by Victor Qiu 1C
Sun Nov 08, 2020 7:49 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 2A.1 Question
Replies: 1
Views: 22

Re: 2A.1 Question

This is because when we count valence electrons, we only count the electrons that are in the outer shell. The electrons whose principle quantum number is the greatest are in the outer shell. What does that mean? The electron configuration for Sb is [Kr]4d 10 5s 2 5p 3 , 5>4, that means the electrons...
by Victor Qiu 1C
Sun Nov 08, 2020 7:40 am
Forum: Lewis Structures
Topic: 2B.11 part C
Replies: 1
Views: 28

Re: 2B.11 part C

It follows the same principle, but there are some tips. Carbon is always on the backbone, and for -COOH, it is always like C forms a single bond with an O, and for this O, it forms another single bond with H and has 2 pairs of electrons surrounding it, and for another O, it forms a double bond with ...
by Victor Qiu 1C
Sun Nov 08, 2020 7:24 am
Forum: Lewis Structures
Topic: 2.B 5 part b
Replies: 1
Views: 13

Re: 2.B 5 part b

Br has 7 valence electrons while O has 6, and because it is BrO - , there should be 7+6+1=14 electrons in total. If there is a double bond, there should be 10 electrons that do not form bonds surrounding Br and O. When there is a double bond, Br allows 2 pairs of electrons around it, and O also allo...
by Victor Qiu 1C
Sun Nov 01, 2020 5:09 am
Forum: Significant Figures
Topic: Sig Figs for electron shells
Replies: 4
Views: 73

Re: Sig Figs for electron shells

I think you can just add "Because electron shells are integers, the number is ...".
by Victor Qiu 1C
Sun Nov 01, 2020 4:51 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Thorium and Silver
Replies: 4
Views: 48

Re: Thorium and Silver

Examples should include
Cu [Ar]3d104s1
and the elements around 4d and 5s
Y [Kr] 4d15s2
Zr [Kr] 4d25s2
Nb [Kr] 4d45s1
Mo [Kr] 4d55s1
Tc [Kr] 4d55s2
Ru [Kr] 4d75s1
Rh [Kr] 4d85s1
Pd [Kr] 4d10
Ag [Kr] 4d105s1
Cd [Kr] 4d105s2
by Victor Qiu 1C
Sun Nov 01, 2020 4:33 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Shorthand Electron Configurations
Replies: 6
Views: 48

Re: Shorthand Electron Configurations

It is always helpful to memorize the elements right after the noble gas elements.
Li [He]2s1
Na [Ne]3s1
K [Ar]4s1
Rb [Kr]5s1
Cs [Xe]6s1
Fr [Rn]7s1
by Victor Qiu 1C
Sun Nov 01, 2020 4:17 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Writing out electron configurations
Replies: 5
Views: 54

Re: Writing out electron configurations

Yes, I agree with Sydney_Lam3G. For example, we can just write 1s22s22p6 for Ne.
by Victor Qiu 1C
Sun Nov 01, 2020 4:10 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Ground State Electron Configuration
Replies: 4
Views: 47

Re: Ground State Electron Configuration

For example, if 1s22s12p3 is the excited state, 1s22s22p2 would be the ground state.
by Victor Qiu 1C
Sun Oct 25, 2020 11:24 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Equation and Negative Signs
Replies: 11
Views: 104

Re: Rydberg Equation and Negative Signs

If an electron jumps from a high state of energy to a low energy state, the change in energy is negative because this process release energy. However, when we use the energy later to calculate either the frequency or the wavelength, we usually do not include the negative sign, or you can understand ...
by Victor Qiu 1C
Sun Oct 25, 2020 11:14 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: When would 3d orbital be filled before the 4s orbital?
Replies: 8
Views: 127

Re: When would 3d orbital be filled before the 4s orbital?

It would go as 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p
by Victor Qiu 1C
Sun Oct 25, 2020 11:09 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 1E.25
Replies: 3
Views: 140

Re: 1E.25

I think Jordan Young's answer is correct. To make an example, we would write [Ar]3d104s1 for Cu instead of 1s22s22p63s23p63d104s1
by Victor Qiu 1C
Sun Oct 25, 2020 11:00 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Sapling Question 16
Replies: 3
Views: 41

Re: Sapling Question 16

I think Megan Chan's answer is correct. Just to add on it, neon's electron configuration can also be represented as [He]2s22p6
by Victor Qiu 1C
Sun Oct 25, 2020 7:16 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: 1B.25 Second Part
Replies: 2
Views: 52

Re: 1B.25 Second Part

Because it's one dimensional, there will only be lines. Imagine that there is only an x-axis. The box will only have a line segment that represents its diameter.
by Victor Qiu 1C
Sun Oct 18, 2020 4:45 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Equation and Empirical Equation
Replies: 4
Views: 29

Re: Rydberg Equation and Empirical Equation

Yes, the Rydberg Equation works for Hydrogen only, because it is based on Bohr's model which is specifically about the electrons in hydrogen atoms. There is a more complex equation 1/λ = RZ 2 ((1/n 1 2 ) - (1/n 2 2 )) that can be used for other one-electron (meaning one electron affected by nuclear ...
by Victor Qiu 1C
Sun Oct 18, 2020 4:31 pm
Forum: Properties of Light
Topic: Example during lecture 6
Replies: 5
Views: 90

Re: Example during lecture 6

If an electron jumps from a high state of energy to a low energy state, the change in energy is negative because this process release energy. However, when we use the energy later to calculate either the frequency or the wavelength, we usually do not include the negative sign, or you can understand ...
by Victor Qiu 1C
Sun Oct 18, 2020 9:08 am
Forum: Photoelectric Effect
Topic: Question about Short Wavelengths vs. Long Wavelengths
Replies: 6
Views: 80

Re: Question about Short Wavelengths vs. Long Wavelengths

What Ashley said is correct. In short, energy per photon needs to be great enough so that it can "take away" an electron. Therefore, if a light cannot eject electrons, that means per photon energy is not great enough. Lower wavelength means greater energy. If a light with lower wavelength ...
by Victor Qiu 1C
Sun Oct 18, 2020 8:46 am
Forum: Properties of Light
Topic: energy level transfer
Replies: 4
Views: 45

Re: energy level transfer

So our eyes work like this: after light hits the retina, photoreceptors turn the light into electrical signals, and our brain tells us that "there is light". Therefore, when at excited state, there is no photon emitted, which means there is no light hitting the retina. Therefore, it's not ...
by Victor Qiu 1C
Sun Oct 18, 2020 5:28 am
Forum: Properties of Light
Topic: Need help on 1.16
Replies: 4
Views: 794

Re: Need help on 1.16

1/λ = RH (1/n12 - 1/n22)
1/λ × 1/RH = (1/n12 - 1/n22)
(1/n12 - 1/n22) = 1/(4.34 × 10-7) × 1/(1.096776 × 107) = 0.21
0.21 = 1/4 - 1/25
4 = 22, 25 = 52
Therefore, n2 = 5, n1 = 2
by Victor Qiu 1C
Fri Oct 09, 2020 9:04 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Confidence Interval and Accuracy & Precision
Replies: 5
Views: 62

Re: Confidence Interval and Accuracy & Precision

Victor, that's a novel way of thinking about confidence intervals and I definitely never had that thought occur to me. It took me a couple tries, but I think I understood what you're trying to get at in general. which makes the former more precise while the latter more accurate I'm confused about t...

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