CHEMISTRY COMMUNITY

Paige Lee 1A

For part C, could someone please explain why, as pH increases, [OH-] increases, so the reaction rate decreases? a) What is the overall reaction for the following mechanism? ClO2 1 H2O ∆ HClO 1 OH2 HClO 1 I2 ¡ HIO 1 Cl2 HIO 1 OH2 ∆ IO2 1 H2O (fast equilibrium) (very slow) (fast equilibrium) (b) Write...

Paige Lee 1A

For part E, could someone please explain why adding a catalyst to accelerate the 3rd step only would have no effect on overall reaction rate? Refer to the illustration below for the reaction A S D. (a) How many steps does this reaction have? (b) Which is the rate- determining step in this reaction? ...

Paige Lee 1A

Could someone please explain how to get part c, 10.9 grams? I got that 0.777mols/L remain, but I'm having trouble converting this to grams Sulfuryl chloride, SO2Cl2, decomposes by first-order kinetics, and kr 5 2.81 3 1023 min21 at a certain temperature. (a) Determine the half-life for the reaction....

Paige Lee 1A

For part C, could someone please explain how to get [A]= 0.085 mols/L? I understand how to get 0.068mols/L, but I don't understand why you subtract it from the starting amount 0.153mol/L for A concentration Determine the rate constant for each of the following first- order reactions, in each case ex...

Paige Lee 1A

For part c, I keep getting 2.85, instead of 2.85*10^-12. But I got the correct answer for part d using 2.85. Is there a typo in the textbook? The following data were obtained for the reaction A 1 B 1 C S products: Initial concentration, [J]initial/(mmol·L21) Initial rate/ Experiment A B C ((mmol)·L2...

Paige Lee 1A

Yes, I'm pretty sure there are other errors other than the ones that he listed in the document that he posted

Paige Lee 1A

If you use the equation Ecell = E°cell - RT/F * ln(10) * log[H+], then I don't think the number of moles of e- matters

Paige Lee 1A

Cathode: Ni2+(aq) + 2e- → Ni(s)
Anode: 2H2O(l) → O2(g) + 4H+ (aq) + 4e- (since the O in SO4 gets oxidized)
E°cell = E°cathode - E°anode
-0.23V - 1.23V = -1.46V

Paige Lee 1A

I'm pretty sure the anode is supposed to be the M2+/M

Paige Lee 1A

They are separated with a comma because they're both in the same phase

Paige Lee 1A

For this question, you would want to find the least reduction potential as that implies that it is better as an oxidizing agent and thus will be better at reducing other compounds. What was your method for trying to solve this problem? I arranged the metals in order of decreasing E/V according to a...

Paige Lee 1A

Could someone please explain how to do this problem? I'm mostly confused about which numbers to plug into which formulas.
What range (in volts) does a voltmeter need to have to measure pH in the range of 1 to 14 at 25 degreesC if the voltage is zero when pH =7?

Paige Lee 1A

Could someone please explain why you take the square root of K to get Ka?

Use the data in Appendix 2B and the fact that, for the half- reaction F2(g) 1 2 H1(aq) 1 2 e2 S 2 HF(aq), E8 5 13.03 V, to calculate the value of Ka for HF.

Paige Lee 1A

Could someone please explain why for part B, n=1 and not n=2? I got that the two half reactions were: H2(g)→2H+(aq)+2e- and 2H+(aq)+2e- →H2(g) Why is only 1 e- involved and not 2e-? Calculate Ecell for each of the following concentration cells: (b) Pt(s)|H2(g, 1 bar)|H1(aq, pH 5 4.0)||H1(aq, pH 5 3....

Paige Lee 1A

Could someone please explain for part C, how/why do you include the partial pressures of H2 and Cl2 gases in the lnQ?

Predict the potential of each of the following cells:
c. Pt(s)|Cl2(g, 250 Torr)|HCl(aq, 1.0 mol/L) || HCl(aq, 0.85 mol/L) | H2(g, 125 Torr)|Pt(s)

Paige Lee 1A

For this question, we are supposed to arrange the metals in order of decreasing E/V, right? For part A I keep getting Cu, Fe, Zn, Cr For part C I keep getting V, Ti, Al, U For part D I keep getting Au, Ag, Sn, Ni I'm not sure what I keep doing wrong? Arrange the following metals in order of increasi...

Paige Lee 1A

Could someone please explain for part C, how "KOH" got introduced into the cell diagram? It wasn't in the equation that was given. Write the half-reactions and devise a galvanic cell (write a cell diagram) to study each of the following reactions: C. Cd(s) + 2 Ni(OH)3 (s) → Cd(OH)2 (s) + 2...

Paige Lee 1A

Could someone please explain how to get the half reactions for part D of this question?

Write the half-reactions, the balanced equation for the cell reaction, and the cell diagram for each of the following skeletal equations:
D. Au+(aq) → Au(s) + Au3+(aq)

Paige Lee 1A

For part D, could someone please explain how to get the half reactions for this cell?

Write the half-reactions and the balanced equation for the cell reaction for each of the following galvanic cells:
D. Pt(s)|O2(g)|H+(aq)||OH-(aq)|O2(g)|Pt(s)

Paige Lee 1A

Could someone please explain why the correct answer is B? For the # of moles, I keep getting 0.1 moles in total for A, and then 0.2 moles in total for B, C, and D each Which combination of solutions of HCL and NaOH would produce the largest delta T? A. 50mL of 1M HCl with 50mL of 1M NaOH B. 50mL of ...

Paige Lee 1A

Could someone please explain why solids are included in the equilibrium constant equation for this problem? The drug amphetamine is usually marketed at hydrogen bromide salt because it is much more stable in this solid form. When the drug is ingested as a salt (solid form), it enters the stomach, wh...

Paige Lee 1A

What are the half reactions for part D? How do you get the oxidation reaction from just Cl2 on the reactants side? D. Cl2(g) → HClO(aq) + Cl2(g) Balance each of the following skeletal equations by using oxidation and reduction half-reactions. All the reactions take place in acidic solution. Identify...

Paige Lee 1A

Could someone please explain why the answer is -1?

At pH 6, what is the net charge for acetic acid, CH3COOH (pKa=4.75)?

Paige Lee 1A

Could someone please explain why the correct answer is B?

Which combination of solutions of HCL and NaOH would produce the largest delta T?
A. 50mL of 1M HCl with 50mL of 1M NaOH
B. 50mL of 2M HCl with 50mL of 2M NaOH
C. 100mL of 1M HCl with 50mL of 2M NaOH
D. 100mL of 1M HCl with 100mL of 1M NaOH

Paige Lee 1A

Could someone please explain why the concentrations of reactants and products approach their own respective equilibriums? Also, why in the answer key is I2 the product and I the reactant?

Depict the progress of the reaction graphically (as in Fig. 5G.1) for the reaction in Exercise 5G.13.

Paige Lee 1A

Work is negative when energy is leaving the system

Paige Lee 1A

Maximum potential difference occurs when very little current flows. As the current approaches 0, the maximum potential difference converges to E (electromotive force of cell)

Paige Lee 1A

Could someone please explain the answers for parts B and C?
Using values in Appendix 2A, calculate the standard Gibbs free energy for the vaporization of water at 25.0 8C, 100.0 8C, and 150.0 8C. (b) What should the value at 100.0 8C be? (c) Why is there a discrepancy?

Paige Lee 1A

Could someone please explain the "reference point" concept?

Some entries for Sm8 in Appendix 2A are negative. What is common about these entries, and why would the entropy be negative?

Paige Lee 1A

For part E, could someone please explain what the answer key means by "dispersal of matter?"
The question was "What is the driving force for the dissolution of KNO3?"

Paige Lee 1A

Find the amount of heat transferred to ice in 0.5hrs using q=mCdeltaT. You will get 3135J transferred in 0.5 hrs. Then use dimensional analysis to find how many joules are transferred in 10hrs. You get 62.7kJ transferred in 10hrs. Then divide 62.7kJ by 8.33 moles and get 7.53kJ/mol for enthalpy of f...

Paige Lee 1A

It's on north campus towards the back end of the sculpture garden. It's a big white colored building.

Paige Lee 1A

Given the main reaction, find the sum of the entropies, enthalpies, etc. of the reactants and products

Paige Lee 1A

Could someone please explain why for B and C you know that the reactions are spontaneous everywhere and nonspontaneous everywhere respectively? Why don't you calculate the maximum temperature cut off? Why are parts B and C different from part A of this question? Assume that DH8 and DS8 are independe...

Paige Lee 1A

Could someone please explain why the deltaH for part A is subtracts the Hf of products minus reactants? Why don't we add them together? Why is the correct answer -196.1kJ/mol and not -947.22kJ/mol? Calculate the standard reaction entropy, enthalpy, and Gibbs free energy for each of the following rea...

Paige Lee 1A

For parts A and D, why must w=0 in an adiabatic process?

Paige Lee 1A

I'm not entirely sure if this answers your question, but the problem did say that no heat is lost to the surroundings

Paige Lee 1A

The internal energy of a system increased by 982 J when it was supplied with 492 J of energy as heat. (a) Was work done by or on the system? (b) How much work was done? For part b, I keep getting 490J, but the answer key in the back of the book says 90*10^2J? Could someone please explain how to get ...

Paige Lee 1A

A constant-volume calorimeter was calibrated by carrying out a reaction known to release 3.50 kJ of heat in 0.200 L of solu- tion in the calorimeter (q 5 23.50 kJ), resulting in a temperature rise of 7.32 8C. In a subsequent experiment, 100.0 mL of 0.200 m HBr(aq) and 100.0 mL of 0.200 m KOH(aq) wer...

Paige Lee 1A

Could someone please explain why part c is 8J and not 28J? Also how do you get 8J? Air in a bicycle pump is compressed by pushing in the handle. The inner diameter of the pump is 3.0 cm and the pump is depressed 20. cm with a pressure of 2.00 atm. (a) How much work is done in the compression? (b) Is...

Paige Lee 1A

Calculate the standard enthalpy of formation of dinitro- gen pentoxide from the following data: 2 NO(g) 1 O2(g) ¡ 2 NO2(g) ¢H° 5 2114.1 kJ 4 NO2(g) 1 O2(g) ¡ 2 N2O5(g) ¢H° 5 2110.2 kJ and from the standard enthalpy of formation of nitric oxide, NO (see Appendix 2A). Could someone please explain why ...

Paige Lee 1A

Could someone please explain how to get the correct answers for this question? For part a, I keep getting 330K and for part b, I keep getting 343K 4C.3 Calculate the final temperature and the change in enthalpy when 765 J of energy is transferred as heat to 0.820 mol Kr(g) at 298 K and 1.00 atm (a) ...

Paige Lee 1A

That is correct the O2 and N2 are diatomic gases in their most stable form and thus their standard enthalpy of formation is zero. Using the enthalpies of formation we calculate that CO2 requires -393.51 kJ/mol while H20 requires -241.82. Given TNT's enthalpy of formation we calculate: 28(-393.51 kJ...

Paige Lee 1A

Something that might help is writing down what you are given from the problem and what you are trying to solve for. This may help you decide which formula to use and which units to try to get

Paige Lee 1A

Could someone please explain how to get the correct answer? The enthalpy of formation of trinitrotoluene (TNT) is 267 kJ?mol21, and the density of TNT is 1.65 g?cm23. In princi- ple, it could be used as a rocket fuel, with the gases resulting from its decomposition streaming out of the rocket to giv...

Paige Lee 1A

Could someone please explain how to get the correct answer for part b? I keep getting 2.06kJ The reaction of 1.40 g of carbon monoxide with excess water vapor to produce carbon dioxide and hydrogen gases in a bomb calorimeter causes the temperature of the calorimeter assembly to rise from 22.113 deg...

Paige Lee 1A

What are the correct answers for this question? The answer key just says the answer is 373K, but there are four parts to this question. 4C.3 Calculate the final temperature and the change in enthalpy when 765 J of energy is transferred as heat to 0.820 mol Kr(g) at 298 K and 1.00 atm (a) at constant...

Paige Lee 1A

Ka and Kb are specific to a reaction at a specific temperature

Paige Lee 1A

I think you should try to exclude the x value if K is slightly less than 10^-3. But still make sure to check that the percent ionization is less than 5% for a valid approximation

Paige Lee 1A

I like to do the quadratic equation in small, separate parts to make sure I don't mess up. The first calculations I do are the b^2 and 4ac. The second set of calculations I do is solving for what is inside the radical and then taking the square root of it. After that, I add/subtract -b to/from that ...

Paige Lee 1A

Rank the following solutions in order of increasing pH: (a) 1.0 3 1025 m HCl(aq); (b) 0.20 m CH3NH3Cl(aq); (c) 0.20 m CH3COOH(aq); (d) 0.20 m C6H5NH2(aq). Justify your ranking.

Paige Lee 1A

Hemoglobin (Hb) molecules in blood carry O2 molecules from the lungs, where the concentration of oxygen is high, to the tissues where it is low (see the Interlude following Focus 5). In the tissues the equilibrium H3O1(aq) 1 HbO22 (aq) ∆ HHb(aq) 1 H2O(l) 1 O2(aq) releases oxygen. When muscles work h...

Paige Lee 1A

Could someone please explain the reasoning behind part A in question 6.19?

Paige Lee 1A

Could someone please explain how to find the pH for parts a and d?
What are the correct pHs for parts a and d?

Paige Lee 1A

For part d for the percent protonation, I got 1.49% instead of 2.5%
I got the correct values for the pOH and pH though
Could someone please explain how to get 2.5%?

Paige Lee 1A

I found on the internet that the Kc value for the forward rxn is actually 5.9*10^-3. So, for the reverse rxn, the Kc value would be 1.69*10^2
Using these values, I got pretty similar values of concentrations as the solution manual

Paige Lee 1A

Could someone please explain how to get the answers to parts a.ii and b?
I understand how to get part a.i

Paige Lee 1A

Could someone please explain how to fill in the table for solutions 1 and 2?
I got that the concentrations were 1.50mol/L and 6.67*10^-15
I got that the pHs and pOHs for these two solutions were -0.18 and 14.18

Paige Lee 1A

100g of C is 8.326 moles of C Set up an ICE table Initial C: 8.326/50 = 0.16652 Initial H2O: 2.5/50 = 0.05 Initial CO: 0 Initial H2: 0 Change: -x for C and H2O, +x for CO and H2 Equilibrium C: 0.16652-x Equilibrium H2O: 0.05-x Equilibrium CO and H2: both are x, which is given to be 0.04 Plug x=0.04 ...

Paige Lee 1A

For part A, I found the equilibrium concentrations when V=1L.
For part B, I found the equilibrium concentrations when V=0.5L.

For part A I got 0.01 for x instead of 0.0065
For part B I got 0.02 for x instead of 0.015

I'm not sure where I went wrong?

Paige Lee 1A

Could someone please explain how to get the correct answers for parts a and b?

Paige Lee 1A

Could someone please explain how we know that the reaction in part B is endothermic?

Paige Lee 1A

Could someone please explain why parts D and E have different answers? Why is part E not "no change" also?

Paige Lee 1A

A mixture of 2.5 moles H2O and 100 g of C are placed in a 50 L container and allowed to come to equilibrium subject to the following reaction: C(s) + H2O (g) ⇌ CO (g) + H2 (g). The equilibrium concentration of hydrogen is found to be [H2] = 0.040 M. Calculate the equilibrium constant Kc of this reac...

Paige Lee 1A

Could someone please explain how to get the answer for part C?

Paige Lee 1A

Could someone please explain how to find the equilibrium concentration of H2S? Why isn't is 0.2mols/L also?

Paige Lee 1A

Could someone please explain how to get the correct answers for parts b and c?

Paige Lee 1A

For this example, how do you know to find the partial pressures and not the concentrations at equilibrium?

Paige Lee 1A

Could someone please explain how to get part a? I keep getting 13.9 instead of 6.9

Paige Lee 1A

Could someone please explain how to get the correct answer?
I keep getting 4.21*10^-6 mols/L

Paige Lee 1A

Could someone please explain how to find the value of R in this example?
I understand how to get that T=673K, K=3.1*10^4, and Δnt= -1

Paige Lee 1A

Is it possible to problem 5G.11 without having read section 5G.4? Because the syllabus says to omit section 5G.4

Paige Lee 1A

Could someone please explain the reasoning behind the correct answer for part C?

Paige Lee 1A

For #1c on mini marshmallow, how do you know to choose NH4+ and not NO3- for the net ionic equation? Since they're both weak acids and bases

Paige Lee 1A

a. K3[Cr(CN)6]
b. [Co(NH3)5SO4]Cl
c. [Co(NH3)4(OH2)2]Br3
d. Na[Fe(C2O4)2(OH2)2]

Paige Lee 1A

Using En=-hR/n^2, write this expression twice, and make one nfinal and one ninitial. Then, switch to the form E=R{1/n1^2 - 1/n2^2}. To solve for n2^2, divide both sides by R, subtract 1/n1^2, multiply by -1, take square root

Paige Lee 1A

KF has F- (conjugate base of weak acid) which forms basic solutions
KBr has Br- (anion of strong acid) which has no significant effect on pH of solutions

Paige Lee 1A

I think he said weak acids and bases do affect pH

Paige Lee 1A

Could someone please explain how you know to use pKa1, pKa2, pKa3, etc. to find the pH?
Will you always be given these values, or do you need to know how to solve for pKa values?

Paige Lee 1A

For part b, why is formic acid stronger than acetic acid?

Paige Lee 1A

Why is the pH of acid #1 0.176? Why isn't it -0.176?
Isn't the formula for pH: -log[H3O+] ? So why isn't the pH negative after you plug in 1.50mols/L for the [H3O+]?

Paige Lee 1A

I understand how to get 1.6 for part A, but how do you get 1.7 for part B?

Paige Lee 1A

Could someone please explain why part d is amphoteric? Isn't Bi a metal, so why isn't it basic?

Paige Lee 1A

When do you write "ferrate," "ferrous," and "iron(oxidation state)" ?

Paige Lee 1A

Could someone please explain why the coordination number of [Co(Ox)3]3- is 6?
If "ox" represents EDTA, which is hexadentate, why isn't the coordination number 18 because there are three Oxs?

Paige Lee 1A

Could someone please explain to determine the denticity of a ligand based on its Lewis structure?

Paige Lee 1A

pKa represents various Ka values on a logarithmic scale, where pKa=-log[Ka] and p=-logbase 10

Paige Lee 1A

If the overall charge is negative, put the ion in front of the [] brackets
If the overall charge is positive, put the ion after the [] brackets

Paige Lee 1A

Do we need to know how to write net ionic equations?

Paige Lee 1A

Could someone please explain why the coordination number for part d is 6?

Paige Lee 1A

Could someone please explain how to determine which ligands are polydentate? I drew out all the Lewis structures for this question, but I don't know where to go from there

Paige Lee 1A

Could someone please explain the reasoning behind the name "aquapentacyanocolbaltate(III)" for part c?

Paige Lee 1A

What do we need to know for "lone pairs and the reason for their locations"? I'm not sure what this is referring to

Paige Lee 1A

The size of the molecule affects intermolecular forces. If the molecule is large, it will have more attractive intermolecular forces, which can cause it to change phase and become more condensed (liquid, solid).

Paige Lee 1A

The higher polarizability of a molecule, the stronger intermolecular forces/attractions there will be, so it will be harder to break bonds. Which means its melting point and boiling point will be high.

Paige Lee 1A

I am almost positive that yes, they are all weighed equally in character

Paige Lee 1A

I think you are just supposed to memorize that the bond angles are less than 90 and less than 120

Paige Lee 1A

Could someone please explain why the bond angle for b is 109.5 degrees? Why isn't it 180 degrees/linear?

Paige Lee 1A

Could someone please explain why angle c is 120 degrees? Why isn't it 180 degrees?

Paige Lee 1A

I'm still confused, what about trigonal planar molecules? Don't they have 120 degree bond angles, but no lone pairs?

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