Search found 104 matches

by Katherine Wu 1H
Tue Mar 10, 2020 10:43 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Steps to solve calorimeter problem
Replies: 3
Views: 66

Re: Steps to solve calorimeter problem

you use this equation in order to solve for calorimeter problems because you want the energy of the system, not surroundings
q=CΔT
q=heat energy
C=heat constant
ΔT=change in temperature
by Katherine Wu 1H
Tue Mar 10, 2020 10:34 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 7D.1
Replies: 4
Views: 33

Re: 7D.1

we use ln(k prime/k) = (Ea/R)(1/T-1/T prime) = (Ea/R)((T prime-T)/T(T prime))
ln (k prime/k)=ln(0.87 s^-1/0.76 s^-1)
=(Ea/8.31x10^-3 kJ/K.mol)((1030K-1000K)/(1030Kx1000K))
Ea=((8.31x10^-3kJ/K.mol)(1000K)(1030K)/(1030K-1000K))ln(0.87 s^-1/0.76 s^-1)
=39 kJ/mol
by Katherine Wu 1H
Tue Mar 10, 2020 10:29 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: 7.11
Replies: 1
Views: 38

Re: 7.11

a. The objective is to reproduce the observed rate law. If step 2 is the slow step, if step 1 is a rapid equilibrium, and if step 3 is fast also, then our proposed rate law will be rate=k2[N2O2][H2]. Consider the equilibrium of step 1: k1[NO]^2=k prime[N2O2] [N2O2]=k1/k prime [NO]^2 Substituting in ...
by Katherine Wu 1H
Tue Mar 10, 2020 10:19 pm
Forum: First Order Reactions
Topic: 7.27 half life
Replies: 1
Views: 16

Re: 7.27 half life

use equation for half-life of a first order rxn t1/2=ln 2/k k=ln 2/t1/2 k=0.154 h^-1 ln([A]0/[A]t)=kt [A]/[A]0=e^-kt after two hours this ratio is, [A]/[A]0=e^-(0.154 h^-1)(2 h)=0.735 the mass of phenobarbital that remains after 2 hours is 0.735 x 150 mg = 110 mg. to restore the initial amount 40 mg...
by Katherine Wu 1H
Tue Mar 10, 2020 10:15 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 7.11
Replies: 1
Views: 27

Re: 7.11

the objective is to reproduce the observed rate law. if step 2 is the slow step, if step 1 is a rapid equilibrium, and if step 3 is fast also, then our proposed rate law will be rate= k2[N2O2][H2]. consider the equilibrium of step 1: k1[NO]^2=k prime [N2O2] [N2O2]=k1/k prime[NO]^2 substituting in ou...
by Katherine Wu 1H
Tue Mar 03, 2020 10:44 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: cell diagram question
Replies: 3
Views: 27

Re: cell diagram question

sorry, I meant instead not inside
by Katherine Wu 1H
Tue Mar 03, 2020 10:44 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: cell diagram question
Replies: 3
Views: 27

cell diagram question

Pb(s)|Ni^3+,Ni^2+,H^+(aq)||I^2+(aq)|I(s)|Pb(s)
In this case, should the solids on the right side also have a comma inside of a line like the aqueous on the left?
by Katherine Wu 1H
Tue Mar 03, 2020 10:40 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: calculating K2?
Replies: 3
Views: 63

calculating K2?

The ionic dissociation of water is given by the following rxn: The ΔH° for the rxn is 58 kJ/mol. The Kw for the rxn at 25 celsius is 10^-14. Is a pH of 7 acidic or basic at 10 celsius? 2H2O(l)⇄H3O^+(aq)+OH^-(aq) ln K2/K1=-ΔH°/R [1/T2-1/T1] 25 celsius=298.15K 10 celsius=283.15K 58kJ/mol=58,000 J/mol ...
by Katherine Wu 1H
Tue Mar 03, 2020 10:30 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: calculate largest E cell
Replies: 1
Views: 37

calculate largest E cell

Please write the two species that would give the largest E°cell if assembled in an electrochemical cell. (a) Pt^2+(aq)+2e-→ Pb(s): E°=1.20V Cu^2+(aq)+2e-→ Cu(s) E°=0.34V Pt^2+(aq)+2e-→ Pt(s) E°=1.20V (b) Ti^2+(aq)+2e-→ Ti(s) E°=-1.63V Sn^2+(aq)+2e-→ Sn(s) E°=-0.14V Mg^2+(aq)+2e-→ Mg(s) E°=-2.36V I d...
by Katherine Wu 1H
Tue Mar 03, 2020 10:18 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: change in gibbs free energy
Replies: 4
Views: 65

change in gibbs free energy

Choose the one that best describes the change in Gibbs free energy for the process described; briefly justify your answer using a short sentence. The photosynthesis of glucose inside the chloroplast of an old growth Coastal Redwood tree. ΔG<0 ΔG=0 ΔG>0 I don't understand why the answer isn't ΔG>0?
by Katherine Wu 1H
Sun Mar 01, 2020 11:50 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: calculating pH [ENDORSED]
Replies: 2
Views: 85

calculating pH [ENDORSED]

If cell potential is 0.67 V at 25 celsius, what is pH? [Fe^2+]=0.25M, [MnO4^-]=0.30 M, [Mn^2+]=0.01 M, [Fe^3+]=0.05M 5Fe^(2+)+MnO4^(-)+H^(+) → Mn^(2+)+4H2O+5Fe^(3+) E°=0.74 V The answer should be H^+=0.04347 and pH=1.36, however I get different numbers. Can someone tell me what I'm doing wrong? E=E°...
by Katherine Wu 1H
Sun Mar 01, 2020 11:00 pm
Forum: Balancing Redox Reactions
Topic: 6K.5 part b
Replies: 4
Views: 41

Re: 6K.5 part b

rxn of bromine w/ itself (disproportionation) in aqueous solution: Br2(l)→BrO3^-(aq)+Br^-(aq) Br2(l)+2e-→2Br^-(aq) (balanced half rxn) Br2(l)+6H2O(l)→2BrO3^-(aq) (O balanced) Br2(l)+6H2O(l)+12OH^-(aq)→2BrO3^-(aq)+12H2O(l) (H balanced) Br2(l)+12OH^-(aq)→2BrO3^-(aq)+6H2O(l)+10e- (e-s balanced, the H2O...
by Katherine Wu 1H
Tue Feb 25, 2020 9:32 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: what is value of E°?
Replies: 2
Views: 24

what is value of E°?

Consider the following unbalanced half reaction.
Ag(s)+I^-(aq) →AgI(s)+e-
E°=-0.15 V
AgCl(s)+e- →Ag(s)+Cl^-(aq)
E=+0.22V
What is value of E°?
E°=E°cath-E°anode

I'm confused as to whether it should be 0.22-(-0.15)=0.37V or 0.22-0.15=0.07V.
by Katherine Wu 1H
Tue Feb 25, 2020 9:26 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: predict std. rxn for this galvanic cell
Replies: 1
Views: 31

predict std. rxn for this galvanic cell

Predict the standard potential for the following galvanic cells: Cu(s)|Cu^2+(aq)||Au^2+(aq)|Au(s) Cu^2+(aq)+2e- → Cu(s) E°=0.34V Au^+(aq)+e- → Au(s) E°=1.69V 2Au^+(aq)+2e-→ 2Au(s) Cu(s) → Cu^2+(aq)+2e- E°=-0.34 V (e-s are cancelled out) 2Au^+(aq)+Cu(s) →2Au(s)+Cu^2+(aq) E°=E°cath-E°anode The solutio...
by Katherine Wu 1H
Tue Feb 25, 2020 9:15 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: determining unknown quantity in cell
Replies: 2
Views: 39

determining unknown quantity in cell

Determine the unknown quantity in the cell. E=0.050 V Pb(s)|Pb^2+(aq,?)|Ni^2+(aq, 0.20 mol/L)|Ni(s) Pb^2+(aq)+2e-→Pb(s) E°=-0.13 V Ni^2+(aq)+2e-→Ni(s) E°=-0.23 V Pb(s)→Pb^2+(aq)+2e- Ni^2+(aq)+2e-→Ni(s) e-s are cancelled out Pb(s)+Ni^2+(aq)→Pb^2+(aq)+Ni(s) E°cell=E°cath - E°anode =-0.23V-(+0.13V) =-0...
by Katherine Wu 1H
Sun Feb 23, 2020 3:24 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.7 C
Replies: 2
Views: 38

Re: 6L.7 C

Cd(OH)2(s)+2e- →Cd(s)+2OH^-(aq) E°(anode)=-0.81V Ni(OH)3(s)+e-→ Ni(OH)2(s)+OH^-(aq) E°(cathode)=+0.49V Reversing the anode rxn and multiplying the cathode rxn by 2 yields Cd(s)+2OH^-(aq)→Cd(OH)2(s)+2e- 2Ni(OH)3+2e-→2Ni(OH)2(s)+2OH^-(aq) then, upon addition, 2Ni(OH)2(s)+Cd(s)→Cd(OH)2(s)+2Ni(OH)2(s) o...
by Katherine Wu 1H
Sun Feb 23, 2020 3:16 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Textbook question 4.51
Replies: 1
Views: 36

Re: Textbook question 4.51

b. the value at 100 celsius should be exactly 0, because this is the normal boiling point of water c. the discrepancy arises because the enthalpy and entropy values calculated from the tables are not rigorously constant with temperature. better values would be obtained using the actual enthalpy and ...
by Katherine Wu 1H
Sun Feb 23, 2020 3:03 pm
Forum: Balancing Redox Reactions
Topic: 6K.5 a
Replies: 1
Views: 30

Re: 6K.5 a

O3 (g) →O2(g) O3(g) →O2(g)+H2O(l) (balances O) 2H2O(l)+O3(g) →O2(g)+H2O(l)+2OH^-(aq) (balances H) H2O(l)+O3(g) →O2(g)+2OH^-(aq) (cancels H2O) H2O(l)+O3(g)+2e- →O2(g)+2OH^-(aq) (balances charge) Br^-(aq) →BeO3^-(aq) 3H2O(l)+Br^-(aq) →BrO3^- (balances O) 6OH^-(aq)+3H2O(l)+Br^-(aq) →BrO3^-(aq)+^H2O(l) ...
by Katherine Wu 1H
Sun Feb 23, 2020 2:51 pm
Forum: Balancing Redox Reactions
Topic: 6k. d
Replies: 1
Views: 20

Re: 6k. d

3[P4(s)+8OH-(aq) →4H2PO2^-(aq)+4e-]
P4(s)+12H2O(l)+12e- →4PH3(g)+12OH^-(aq)
4P4(s)+12H2O(l)+24OH^-(aq)+12e- →12H2PO2^-(aq)+4PH3(g)+12OH^-(aq)+12e-
4P4(s)+12H2O(l)+12OH^-(aq) →12H2PO2^-(aq)+4PH3(g)
or
P4(s)+3H2O(l)+3OH^-(aq) →3H2PO2^-(aq)+PH3(g)
P4(s) is both the oxidizing and the reducing agent.
by Katherine Wu 1H
Sun Feb 23, 2020 2:43 pm
Forum: Balancing Redox Reactions
Topic: 6K.3
Replies: 1
Views: 29

Re: 6K.3

Cl2 (g) +2e- → 2Cl^- (aq)
2H2O (l)+2Cl2(g) →2HOCl (aq) +2H^+(aq)+2e-
2H2O(l)+2Cl2(g)+2e- →2HOCl(aq)+2H^+(aq)+2Cl^-(aq)+2e-
or
H2O(l)+Cl2(g) →HOCl(aq)+H^+(aq)+Cl^-(aq)
Cl2 is both the oxidizing and the reducing agent.
by Katherine Wu 1H
Wed Feb 19, 2020 5:32 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: midterm Q4
Replies: 4
Views: 64

midterm Q4

The drug amphetamine, C6H5CH2CH(CH3)NH2 (pKb=3.11), is usually marketed as the hydrogen bromide salt, C6H5CH2CH(CH3)NH3^+Br^-, because it is more stable in this solid form. When the drug is ingested as a salt (solid form), it enters the stomach, which contains digestive fluids at pH=1.7. Will this d...
by Katherine Wu 1H
Wed Feb 19, 2020 5:24 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: midterm 3C
Replies: 4
Views: 66

midterm 3C

A buffer solution made with NH3 and NH4Cl has a pH of 10.1. Which procedure(s) could be used to lower the pH? 1.adding HCl 2. adding HN3 3. adding NH4Cl a. 1 only, b. 2 only, 3. 1 and 3 only, 4. 2 and 3 only I know HCl can be used but I'm a little confused as to why NH4Cl can be used? Does it have a...
by Katherine Wu 1H
Wed Feb 19, 2020 5:16 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: midterm Q1A
Replies: 7
Views: 72

midterm Q1A

2NO(g)+O2(g)⇄2NO2(g)
Does the equilibrium constant change if this reaction is heated, if so, how?
I'm confused as to why K would decrease in this case.
by Katherine Wu 1H
Wed Feb 19, 2020 4:58 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Textbook Problem 4J.17
Replies: 2
Views: 36

Re: Textbook Problem 4J.17

a. deltaH=2deltaH(BF3,g)+3deltaH(H2O,l)-(deltaH(B2O3)+6deltaH(HF,g)) =2(-1137kJ/mol)+3(-285.83kJ/mol)-((-1272.8kJ/mol)+6(-271.1kJ/mol)) =-232.1kJ/mol deltaS=2Sm(BF3,g)+3Sm(H2O,l)-(Sm(B2O3,s)+6Sm(HF,g) =2(254.12J/K.mol)+3(69.91J/K.mol)-(53.97J/K.mol+6(173.78J/K.mol)) =-378.68J/K.mol deltaG=-232.1J/K....
by Katherine Wu 1H
Mon Feb 17, 2020 10:54 pm
Forum: Van't Hoff Equation
Topic: 5.55b [ENDORSED]
Replies: 1
Views: 58

Re: 5.55b [ENDORSED]

5.20 x 10^3 g C x 1molC/12.011 g C = 433 mol C
125 g H2O x 1 mol H2O/18.016 g H2o = 6.94 mol H2O

H2O is limiting. Conc. of H2O = 6.94 mol/10 L = 0.694 mol/L

Kc=[CO][H2]/[H2O] = (x)(x)/(0.694-x)=0.403
x^2=0.280-0.403x
x^2+0.403x-0.280=0
x=+0.364 or -0.766
by Katherine Wu 1H
Mon Feb 10, 2020 3:40 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: q=mCdeltaT vs q=nCdeltaT
Replies: 2
Views: 18

Re: q=mCdeltaT vs q=nCdeltaT

use q=mCdeltaT when the mass is in grams. use q=nCdeltaT when mass is in moles.
by Katherine Wu 1H
Mon Feb 10, 2020 3:39 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: entropy change due to T
Replies: 1
Views: 32

entropy change due to T

Container A is filled with 1.0 mol of the atoms of an ideal monatomic gas. Container B has 1.0 mol of atoms bound together as diatomic molecules that are not vibrationally active. Container C has 1.0 mol of atoms bound together as diatomic molecules that are vibrationally active. The containers all ...
by Katherine Wu 1H
Mon Feb 10, 2020 3:28 pm
Forum: Calculating Work of Expansion
Topic: w=-nRT(ln V2/V1) Derivation
Replies: 3
Views: 31

Re: w=-nRT(ln V2/V1) Derivation

I don't think so, I believe the equations will be given.
by Katherine Wu 1H
Mon Feb 10, 2020 3:26 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Example 4.c.1
Replies: 2
Views: 24

Re: Example 4.c.1

I'm pretty sure you use Cv = 3/2R and Cp=5/2R if it's an ideal gas (monatomic) and you use Cp=7/2R and Cv=5/2R if it's diatomic.
by Katherine Wu 1H
Mon Feb 10, 2020 12:54 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: heat capacity question
Replies: 1
Views: 18

heat capacity question

The enthalpy of combustion of benzoic acid, C6H5COOH, which is often used to calibrate calorimeters, is -3227 kJ/mol. When 1.453 g of benzoic acid was burned in a calorimeter, the temperature increased by 2.265 celsius. What is the heat capacity of the calorimeter? The answer says to use q=CΔT to so...
by Katherine Wu 1H
Mon Feb 10, 2020 12:38 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: q=CΔT
Replies: 5
Views: 42

q=CΔT

Is the specific heat capacity used primarily for calorimeter calculations?
by Katherine Wu 1H
Fri Jan 31, 2020 11:46 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4D.21 c.
Replies: 1
Views: 11

Re: 4D.21 c.

delta H= delta H[K2S + 2(H2O)] - delta H[H2S + 2(KOH)]
=[-417.5kJ/mol+2(-285.83kJ/mol)] - [-39.7kJ/mol + 2(-482.37 kJ/mol)]
by Katherine Wu 1H
Fri Jan 31, 2020 11:42 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4E.5
Replies: 3
Views: 31

Re: 4E.5

For the benzene ring, you are supposed to use the single/double resonance bond enthalpy (518 kJ) for all six of the bonds.
by Katherine Wu 1H
Fri Jan 31, 2020 11:40 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Homework 4C.9
Replies: 2
Views: 24

Re: Homework 4C.9

The heat change will be made up of two terms: one term to raise the temperature of the copper and the other to raise the temperature of the water:
q=(400.0g)(4.18J/celsius.g)(100.0celsius - 22.0celsius) + (500.0g)(0.38J/celsius.g)(100.0celsius-22.0celsius)
by Katherine Wu 1H
Fri Jan 31, 2020 11:38 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Test 1
Replies: 1
Views: 42

Re: Test 1

I think the tests for slightly different depending on what discussion you were in. This is #5 on my test. The pKb of fluoride is 10.8. A 0.12 M solution of hydrogen fluoride was made for silicon wafer processing. What is the pOH of this solution at equilibrium? HF(aq)+H2O⇋F^-(aq)+H3O^+ pKa=14 - 10.8...
by Katherine Wu 1H
Fri Jan 31, 2020 11:28 pm
Forum: Phase Changes & Related Calculations
Topic: 4C.13
Replies: 2
Views: 37

Re: 4C.13

The heat gained by the water in the ice cube will be equal to the heat lost by the initial sample of hot water. The enthalpy change for the water in the ice cube will be composed of two terms: the heat to melt the ice at 0 celsius to the final temperature. heat (ice cube) = (50g/18.02 g.mol^-1)(6.01...
by Katherine Wu 1H
Fri Jan 31, 2020 5:14 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4A.11
Replies: 3
Views: 22

4A.11

A calorimeter was calibrated with an electric heater, which supplied 22.5 kJ of energy as heat to the calorimeter and increased the temperature of the calorimeter and its water bath from 22.45 celsius to 23.97 celsius. What is the heat capacity of the calorimeter? The answer says to use: C = 22.5 kJ...
by Katherine Wu 1H
Fri Jan 31, 2020 12:57 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reversible Reactions
Replies: 5
Views: 40

Re: Reversible Reactions

I think a reversible reaction is a reaction where the products are able to react together to form the reactant and vice versa.
by Katherine Wu 1H
Fri Jan 31, 2020 12:50 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: benzene mean bond
Replies: 1
Views: 16

benzene mean bond

Does the 518 kJ/mol bond enthalpy for the carbon double/single apply for only benzene or does it also apply for other possible structures?
by Katherine Wu 1H
Fri Jan 31, 2020 12:29 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.9
Replies: 2
Views: 36

4D.9

The enthalpy of formation of trinitrotoluene (TNT) is -67 kJ/mol, and the density of TNT is 1.65 g/cm^-3. In principle, it could be used as a rocket fuel, with the gases resulting from its decomposition streaming out of the rocket to give the required thrust. In practice, of course, it would be extr...
by Katherine Wu 1H
Thu Jan 30, 2020 9:51 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Ka and percent ionization problem
Replies: 2
Views: 26

Ka and percent ionization problem

The pH of a 0.010 M solution of hydrofluoric acid is 2.63. What are Ka and percent ionization? [H^+]=10^-2.63= 2.344 x 10^-3 HF + H2O ⇋ F^- +H3O^+ I 0.010 / 0 0 C 0.010 - 2.344 x 10^-3 / E 7.656 x 10^-3 / 2.344x10^-3 Ka = (2.344 x 10^-3)^2/(7.656x10^-3) =7.18x10^-4 % ionization: (2.344x10^-3)^2/(7.6...
by Katherine Wu 1H
Thu Jan 16, 2020 8:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: equilibrium concentration
Replies: 1
Views: 17

equilibrium concentration

A reaction mixture is prepared by mixing 0.100 mol SO2, 0.200 mol NO2, 0.100 mol NO, and 0.150 mol SO3 in a 5.00 L reaction vessel. The reaction SO2 (g) + NO2 ⇌ NO(g) + SO3 (g) if allowed to reach equilibrium at 460 celsius, when Kc = 85.0. What is the equilibrium concentration of each substance? Th...
by Katherine Wu 1H
Wed Jan 15, 2020 5:53 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: solubility
Replies: 3
Views: 36

solubility

How do you use equilibrium constants to predict solubility?
by Katherine Wu 1H
Wed Jan 15, 2020 5:52 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: biological examples
Replies: 2
Views: 43

biological examples

What do we need to know about the biological examples: osmotic pressure and ATP hydrolysis?
by Katherine Wu 1H
Wed Jan 15, 2020 5:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: effect on K
Replies: 3
Views: 17

effect on K

Calculate the effect on K of multiplying the chemical equation by a factor.
I'm confused as to what this is asking about/referring to?
by Katherine Wu 1H
Wed Jan 15, 2020 5:47 pm
Forum: Ideal Gases
Topic: approximate ideal gas law
Replies: 3
Views: 35

approximate ideal gas law

Identify reactions where the ideal gas law can be used as an approximation.
I'm a bit confused as to what this is referring to?
by Katherine Wu 1H
Fri Jan 10, 2020 9:43 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: predicting effects
Replies: 9
Views: 121

predicting effects

The two air pollutants SO2 and NO2 can react in the atmosphere as follows: SO2 (g) + NO2 (g) ⇌ SO3 (g) + NO (g) Predict the effect of the following changes to the amount of NO when the reaction above has come to equilibrium in a stainless steel bulb equipped with entrants for chemicals. i. the amoun...
by Katherine Wu 1H
Thu Jan 09, 2020 3:58 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: equilibrium and forming/decomposing
Replies: 2
Views: 20

equilibrium and forming/decomposing

The equilibrium constant, Kp, for the reaction SO2 (g) + O2 (g) ⇌ SO3 (g) at 700 K is 3 x 10^4. A mixture of SO2, O2, and SO3, each at 65 bars was introduced into a container at 700 K. Is the reaction at equilibrium? If not, does SO3 tend to form or decompose? I'm a little confused as to how to dete...
by Katherine Wu 1H
Thu Jan 09, 2020 3:47 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: determining shift in equilibrium
Replies: 4
Views: 35

determining shift in equilibrium

Determine the shift in equilibrium position, if any, which will occur when the temperature is increased. The hydrolysis of ATP: ATP(aq) + H2O (l) ⇌ ADP + PO4^-2(aq) delta H°= -30 kJ/mol The answer says that it shifts to the left. Do I just take into account the delta to determine the shift? Also, in...
by Katherine Wu 1H
Thu Jan 09, 2020 3:39 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: calculating the equilibrium concentrations of products and reactants
Replies: 1
Views: 51

calculating the equilibrium concentrations of products and reactants

A vial of SO2 (0.522 mol/L) and O2 (0.633 mol/L) react and reach equilibrium. Calculate the equilibrium concentrations of the products and reactants given that Kc= 5.66 x 10^-10 for this reaction: 2SO2 (g) + O2 (g) ⇌ 2SO3 (g) concentration SO2 O2 SO3 initial 0.522 0.633 0 change -2X -X +2X equilibri...
by Katherine Wu 1H
Thu Jan 09, 2020 3:28 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: calculating reaction quotient
Replies: 3
Views: 29

calculating reaction quotient

Calculate the reaction quotient, Qc, from the following equilibrium data collected in a 3.00 L sealed reaction vessel for the reaction: AsH3 = 5.55 x 10^-4 mol, As= 3.31 x 10^-3 mol, H2= 1.23 x 10^-3 mol. I keep getting the wrong answer when I try to solve this problem. Can someone show me how to ac...
by Katherine Wu 1H
Wed Nov 27, 2019 11:25 pm
Forum: Lewis Acids & Bases
Topic: Conjugates
Replies: 3
Views: 29

Re: Conjugates

the more electroneg. it is, the more acidic it tends to be
by Katherine Wu 1H
Wed Nov 27, 2019 11:23 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate
Replies: 3
Views: 39

Re: Polydentate

polydentate lignads can occupy more than one binding site simultaneously
by Katherine Wu 1H
Wed Nov 27, 2019 11:10 pm
Forum: Amphoteric Compounds
Topic: distinguishing oxides
Replies: 2
Views: 41

distinguishing oxides

State whether the following oxides are acidic, basic, amphoteric: (a) BaO; (b) SO3; (c) As2O; (d) Bi2O3.
I'm not sure how to distinguish between the three?
by Katherine Wu 1H
Tue Nov 26, 2019 10:46 pm
Forum: Lewis Acids & Bases
Topic: writing chemical equation
Replies: 1
Views: 35

writing chemical equation

Either the cation or anion is a weak acid or weak base in water. Write the chemical equation for the proton transfer equation of the cation or anion with water: c. C5H5NHCl The answer says that C5H5NH + H2O ➔ C5H5N +H3O. I'm guessing the forgotten Cl would remain part of the C5H5NH? So, C5H5NHCl + H...
by Katherine Wu 1H
Mon Nov 25, 2019 10:09 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: coordination number
Replies: 3
Views: 39

coordination number

Determine the coordination number of the metal ion in each of the following complexes:
a.[PtCl2(en)2]^2+ and b.[Cr(edta)]^+
The answer for a. is 6 (en is bidentate) and b. is 6 (EDTA is hexadentate). I don't understand how it results in six?
by Katherine Wu 1H
Mon Nov 25, 2019 5:58 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: polydentate
Replies: 2
Views: 36

polydentate

Would something that is polydentate mean that it would have a lot of lone e- pairs?
So between HN(CH2CH2NH2)2, CO3^-2, oxalate, the polydentates would be CO3^-2 and oxalate?
by Katherine Wu 1H
Mon Nov 25, 2019 5:45 pm
Forum: Naming
Topic: ferrate
Replies: 4
Views: 37

ferrate

Writing the formula of this compound: sodium bisoxalato (diaqua) ferrate (III)
What does ferrate refer to?
by Katherine Wu 1H
Mon Nov 25, 2019 5:41 pm
Forum: Naming
Topic: -ide naming
Replies: 1
Views: 27

-ide naming

chloride and bromide mean that they're Cl2 and Br2 right?
by Katherine Wu 1H
Mon Nov 25, 2019 5:36 pm
Forum: Naming
Topic: OH2 naming
Replies: 4
Views: 37

OH2 naming

For [Co(CN)5(OH2)]^-2, would the OH2 be named aqua or would it remain hydroxide?
So, would the name be penta cyano hydroxide cobalt (II) or penta cyano aqua cobalt (II)?
by Katherine Wu 1H
Mon Nov 25, 2019 5:24 pm
Forum: Naming
Topic: roman numerals
Replies: 7
Views: 63

roman numerals

I'm confused to what the roman numeral refers to.
In [Ni(CN)4]^-2, the name is tetracyanonickelate (II), so I'm guessing it refers to the -2?
by Katherine Wu 1H
Sun Nov 17, 2019 9:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: bond angles
Replies: 1
Views: 35

bond angles

In a hydromium ion, I think it would be T-shaped w/ bond angles of <90?
However, the answer is <120, did I identify the shape wrong?
If I did, what is the actual shape and what does it look like?
by Katherine Wu 1H
Sat Nov 16, 2019 11:03 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: identifying pi & sigma bonds
Replies: 3
Views: 51

identifying pi & sigma bonds

How do I tell if a bond is a sigma or pi bond?
by Katherine Wu 1H
Sat Nov 16, 2019 10:56 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR notation
Replies: 8
Views: 73

VSEPR notation

For NO3-, would the VSEPR notation be AX3 or AX4 and why?
by Katherine Wu 1H
Sat Nov 16, 2019 10:54 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR notation
Replies: 6
Views: 83

VSEPR notation

In CH2Cl2, would the VSEPR notation would be AX4?

In PCl3, would the VSEPR notation would be AX3E?

If not, please explain.
by Katherine Wu 1H
Sat Nov 16, 2019 10:11 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: sigma and pi bonds
Replies: 2
Views: 31

sigma and pi bonds

What are sigma and pi bonds and how do I label them?
by Katherine Wu 1H
Mon Nov 11, 2019 2:46 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: hydrogen bonding
Replies: 1
Views: 25

hydrogen bonding

Suggest, giving reasons, which substances in each of the following pairs is likely to have the higher normal melting point (Lewis structure may help your arguments): (c) C2H5OC2H5 (diethyl ether) or C4H9OH (butanol) The answers says that butanol has a higher normal melting point due to hydrogen bond...
by Katherine Wu 1H
Mon Nov 11, 2019 1:43 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: shape of molecule/intermolecular forces
Replies: 3
Views: 36

shape of molecule/intermolecular forces

Account for the following observations in terms of the type and strength of the type and strength of intermolecular forces. (c) The boiling point of pentane, CH3(CH2)CH3, is 36.1 degrees celsius, whereas that of 2,2-dimethylpropane (aka neopentane) C(CH3)4 is 9.5 degrees celsius. The answer says tha...
by Katherine Wu 1H
Mon Nov 11, 2019 12:57 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: intermolecular forces/polarity
Replies: 2
Views: 34

intermolecular forces/polarity

Explain the difference in the boiling points of AsF3 (63 celsius) and AsF5 (-53 celsius).
The answer says that it is clear that AsF3 is a polar molecule while AsF5 is not from the Lewis structures. How do you tell whether a structure is polar or not?
by Katherine Wu 1H
Mon Nov 11, 2019 12:54 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: types of intermolecular forces
Replies: 5
Views: 27

types of intermolecular forces

Identify the types of attractive intermolecular interactions that might arise between molecules of each of the following substances: (a) NH2OH; (b) CBr4; (c) H2SeO4; (d) SO2.

I'm not sure how to know whether or not a molecule has dipole-dipole intermolecular forces.
by Katherine Wu 1H
Tue Nov 05, 2019 4:41 pm
Forum: Lewis Structures
Topic: 7 lewis structure
Replies: 1
Views: 47

7 lewis structure

How important is a 7 lewis structure for CO2 where there's one triple bond and one single bond to the actual structure of CO2?

I don't understand what the question os asking for?
by Katherine Wu 1H
Tue Nov 05, 2019 4:28 pm
Forum: SI Units, Unit Conversions
Topic: converting J to kJ/mol
Replies: 2
Views: 126

converting J to kJ/mol

converting 4.89x10^-17 J to kJ/mol

first convert J to kJ by multiplying by 0.001.
I'm not sure how to do the next part? Do I divide or multiply the number by avogadro?
by Katherine Wu 1H
Tue Nov 05, 2019 4:19 pm
Forum: Photoelectric Effect
Topic: binding energy
Replies: 3
Views: 163

binding energy

An x-ray photon of wavelength 0.989 nm strikes a surface. The emitted electron has a kinetic energy of 969 eV. (1 eV = 1.602 10^-19 J)

Is the binding energy in the question referring to the electron's threshold energy or something else?
by Katherine Wu 1H
Sun Nov 03, 2019 4:40 pm
Forum: Dipole Moments
Topic: drawing dipole moments
Replies: 5
Views: 64

drawing dipole moments

how do you find a dipole moment and how would you draw it?
by Katherine Wu 1H
Sun Nov 03, 2019 4:10 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: polarizing power
Replies: 3
Views: 39

polarizing power

How do you figure out which ion has the most ion polarizing power? For example, with Li^+, Na^+, K^+.
by Katherine Wu 1H
Tue Oct 29, 2019 8:07 pm
Forum: Ionic & Covalent Bonds
Topic: finding chemical formula based on charges of ions
Replies: 1
Views: 29

finding chemical formula based on charges of ions

On the basis of the expected charges on the monatomic ions, give the chemical formula of each of the following compounds.
a. magnesium sulfide
b. indium (III) sulfide
c. aluminum hydride
d. hydrogen telluride
e. bismuth (III) fluoride

I'm confused on where to start.
by Katherine Wu 1H
Fri Oct 25, 2019 9:00 pm
Forum: Ionic & Covalent Bonds
Topic: ion charge
Replies: 3
Views: 29

Re: ion charge

For d. Ga, I don't understand why the answer is Ga^3+?
the ground state configuration I got was [Ar]3d^10 4s^2 4p^1, so I assumed that it would be best to just get rid of the 4p^1, so that it would be [Ar]3d^10 4s^2 and the charge would be Ga^+.
by Katherine Wu 1H
Fri Oct 25, 2019 8:05 pm
Forum: Ionic & Covalent Bonds
Topic: ion charge
Replies: 3
Views: 29

ion charge

Write the most likely charge for the ions formed by each of the following elements:
a. S
b. Te
c. Rb
d. Ga
I don't know where to start.
by Katherine Wu 1H
Thu Oct 24, 2019 10:04 pm
Forum: Ionic & Covalent Bonds
Topic: ground-state configuration of ions
Replies: 4
Views: 48

ground-state configuration of ions

Give the ground-state electron configuration expected for each of the following ions: a. Cu^+ b. Bi^3+ c. Ga^3+ d. Tl^3+ For a, I got [Ar]3d^9 4s^2, which becomes [Ar]3d^10 4s^1. I don't understand why the answer is just [Ar]3d^10? As for b, the answer is [Xe}4f^14 5d^10 6s^2. I'm not sure how to ge...
by Katherine Wu 1H
Thu Oct 24, 2019 4:27 pm
Forum: Ionic & Covalent Bonds
Topic: valence electrons
Replies: 6
Views: 80

valence electrons

Give the number of valence electrons (including d electrons) for each of the following elements:
a. Sb b. Si c. Mn d. B

I think I understand how to find the valence electrons for b, c, and d. Si: 4, Mn: 7, B: 3. I don't understand how the answer for a. (5 electrons) came to be?
by Katherine Wu 1H
Thu Oct 17, 2019 10:26 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: heisenberg, calculating uncertainty in speed
Replies: 1
Views: 35

heisenberg, calculating uncertainty in speed

You are caught in a radar trap and hope to show that the speed measured by the radar gun is in error due to the Heisenberg uncertainty principle. If you assume that the uncertainty in your position +/- 5m when your speed was measured, and that the car has a mass of 2150 kg, what is your calculated u...
by Katherine Wu 1H
Thu Oct 17, 2019 10:05 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: heisenberg, calculating kinetic energy
Replies: 3
Views: 44

heisenberg, calculating kinetic energy

Use the uncertainty in velocity (3.4x10^10 m/s) to calculate the electron's uncertainty in kinetic energy. Then calculate the uncertainty in kinetic energy per mole of electrons (that is, per mole of hydrogen atoms). I'm not quite sure where to start. I tried plugging the velocity and mass of electr...
by Katherine Wu 1H
Thu Oct 17, 2019 9:57 pm
Forum: DeBroglie Equation
Topic: deBroglie, finding wavelike properties
Replies: 2
Views: 43

deBroglie, finding wavelike properties

Calculate the wavelength of a 275 kg single-seat electric car traveling at a speed of 125 km/hr. Do electric cars have wavelike properties? The first thing I do is convert 125 km/hr to m/s. 125 km/hr x 1000m/1km x 1 hr/60s = 2083.33 m/s lambda= (6.63x10^-34 Js)/((275 kg)(2083.33m/s) At the end, I ge...
by Katherine Wu 1H
Thu Oct 17, 2019 9:42 pm
Forum: Properties of Light
Topic: atomic spectra
Replies: 2
Views: 30

atomic spectra

In 1.0 s, a 60 W bulb emits 11 J of energy in the form of infrared radiation (heat) of wavelength 1850 nm. What is the energy per photon of light emitted? How many photons of infrared radiation does the lamp generate in 1.0 s?

I have no idea where to begin/which equations to use.
by Katherine Wu 1H
Thu Oct 17, 2019 9:37 pm
Forum: Properties of Light
Topic: atomic spectra module
Replies: 1
Views: 30

atomic spectra module

The meter was defined in 1963 as 1,650,763.73 wavelengths of radiation emitted by krypton-86 (it has since been redefined). What is the wavelength of this krypton-86 radiation? What is the wavelength of this krypton-86 radiation? To what region of the electromagnetic spectrum does this wavelength co...
by Katherine Wu 1H
Sun Oct 13, 2019 10:42 pm
Forum: Properties of Electrons
Topic: E(photon) equation help
Replies: 2
Views: 39

Re: E(photon) equation help

So after I convert 1509.6 kJ/mol to 150600 J/mol, I convert J/mol to 2.5008 x 10^-19 J.
However when I plug the numbers into the equation,
E(photon)-2.5008x10^-19=1.99x10^-19, I end up with 4.4908x10^-19 J, which is different from the answer 2.501x10^-19 J.
Am I doing something incorrect?
by Katherine Wu 1H
Sun Oct 13, 2019 9:00 pm
Forum: Properties of Light
Topic: photoelectric effect
Replies: 3
Views: 48

photoelectric effect

Which one of following is not describing the photoelectric effect?
A. E (photon) – E (remove e-) = E (excess)

B. E (photon) – E (remove e-) = EK (e-)

C. hv - work function = 1/2mv2

D. λv = c

E. None of the above
I don't understand which of these are not describing the effect and why.
by Katherine Wu 1H
Sun Oct 13, 2019 8:48 pm
Forum: Properties of Electrons
Topic: kinetic energy help
Replies: 1
Views: 35

kinetic energy help

If molybdenum is irradiated with 194 nm light, what is the maximum possible kinetic energy of the emitted electrons?
min. freq.: 1.09x10^15 Hz
min. energy: 7.22x10^-19 J

I don't have a clue where to start from this.
by Katherine Wu 1H
Sun Oct 13, 2019 8:34 pm
Forum: Properties of Electrons
Topic: E(photon) equation help
Replies: 2
Views: 39

E(photon) equation help

How much energy is required to remove an electron from one sodium atom? velocity of ejected electron: 6.61x10^5 m/s work function of sodium: 150.6 kJ/mol kinetic energy of ejected electron: 1.99x10^-19 J I assume that the equation to use is E(photon)-work function=KE(ejected e-) So, E(photon)-150.6 ...
by Katherine Wu 1H
Sun Oct 13, 2019 7:21 pm
Forum: Properties of Electrons
Topic: kinetic energy equation help
Replies: 2
Views: 36

kinetic energy equation help

Light hits a sodium metal surface and the velocity of the ejected electron is 6.61 x 105 m.s-1. The work function for sodium is 150.6 kJ.mol-1. Answer the following three questions. What is the kinetic energy of the ejected electron? I know to use the kinetic energy equation KE=1/2mv^2 but I'm not s...
by Katherine Wu 1H
Sat Oct 05, 2019 7:08 pm
Forum: Molarity, Solutions, Dilutions
Topic: Solution problem
Replies: 3
Views: 50

Re: Solution problem

molarity=moles of solute/volume of solution

the moles of solute would be the numerator, volume would be denominator
by Katherine Wu 1H
Sat Oct 05, 2019 7:05 pm
Forum: Molarity, Solutions, Dilutions
Topic: Molarity and Dilution G23
Replies: 3
Views: 105

Re: Molarity and Dilution G23

just assume that NaCl and KCl are the only two you're using
by Katherine Wu 1H
Sat Oct 05, 2019 6:56 pm
Forum: SI Units, Unit Conversions
Topic: How units of mass effect Scientific notation
Replies: 3
Views: 42

Re: How units of mass effect Scientific notation

if you are converting to grams, then it should be 10^3
by Katherine Wu 1H
Sat Oct 05, 2019 2:45 pm
Forum: Significant Figures
Topic: Sig Figs When Adding and Subtracting
Replies: 3
Views: 62

Re: Sig Figs When Adding and Subtracting

For example, let's say these three numbers: 34.07 g, 70 g, and 60.0 g create the number 7070.3 g 34.07 g has 4 sig figs 70 g has 1 sig fig 60.0 g has 3 sig figs 7070.3 g would be rounded down to 7000 g because you always want to choose the number that has the least amount of sig figs. In this case, ...
by Katherine Wu 1H
Sat Oct 05, 2019 2:40 pm
Forum: Properties of Light
Topic: Electrical Field
Replies: 1
Views: 28

Re: Electrical Field

the electrical field corresponds to the amplitude; as the frequency decreases the waves broaden and the extent of the change (slope of the wave) decreases
by Katherine Wu 1H
Sat Oct 05, 2019 12:47 pm
Forum: Properties of Light
Topic: Classical Mechanics vs. Quantum Mechanics
Replies: 4
Views: 41

Re: Classical Mechanics vs. Quantum Mechanics

In classical mechanics the events tend to be continuous, which is to say they move in smooth, orderly and predictable patterns. In quantum mechanics, the events are unpredictable, which is to say "jumps" occur that involve seemingly random transitions between states.
by Katherine Wu 1H
Sat Sep 28, 2019 10:48 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Molar Mass
Replies: 2
Views: 101

Re: Molar Mass

Subtract the molar mass of the (OH)2 from the metal hydroxide.
74.1 g/mol - 34.02 g/mol = 40.08 g/mol
You get the molar mass of Ca. This is the metal.
So, the molar mass of calcium sulfide (CaS) = 72.15 g/mol
by Katherine Wu 1H
Sat Sep 28, 2019 8:03 am
Forum: Administrative Questions and Class Announcements
Topic: Formatting homework
Replies: 12
Views: 197

Re: Formatting homework

I'm just writing down my answers onto a piece of binder paper. As long as you indicate which question is which, I think that's fine.

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