Intro II Chemistry questions

Question

I'm reviewing for an exam, and I'm having trouble with these questions. I have an answer sheet for them, but not the solutions. Could you help me answer these questions? Please show as much work as you can. Formula's are very important.

Thank you.

1. The rate formation of oxygen in the reaction 2N2O5(g)->4NO2(g) O2(g)

is 2.28(mol )2)*L-1S-1. What is the rate at which N2O5 is used?

2. What is the expected pH of an aqueous solution containing 0.50M CH3COOH (Ka=1.8*10^-5)

3. given A B-> C deltaG=-56.0KJ/mol. What is the equlibrium constant for this reaction.

Answer 1

1. The rate formation of oxygen in the reaction 2N2O5(g)->4NO2(g) O2(

take the rate of formation of O2 & at ratio of 2 mol N2O5 / 1 mol O2 =

the rate of loss of N2O5 will be twice that rate

======================================...

2. What is the expected pH of an aqueous solution containing 0.50M CH3COOH (Ka=1.8*10^-5)

CH3COOH -->  H+  & CH3COO-

[0.50 - x]   ---->  x    &   x

K = [H+] [CH3COO-] / [CH3COOH]

1.8e-5 = [x] [x] / [0.5-x]

since the K is small , 0.50-x simplifies to 0.50 :

1.8e-5 = [x] [x] / [0.5]

x = 3.0e-3

============================

3. given A B-> C deltaG=-56.0KJ/mol. What is the equlibrium constant for this reaction.

dG = -RT lnK

-56,000 joules  = - (8.314)(assume 298Kelvin)(lnK)

lnK = 2.2603

e^x

K = 9.586

your answer is: 9.59