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## ACIDS II

### Resources:

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### Question 1

Suppose you have 0.6 M solution of acid HB. Suppose further that Ka >> 1 for this acid. Which of the following statements is true?

Strong and weak acid defined

Select one:

### Explanation

Ka = [H+][B-]/[HB]

Strong acids have large Ka and will fully dissociate into ions so the answer should be d as the HB should have fully dissociated

### Question 2

Suppose you have 0.6 M solution of acid HB. Suppose further that Ka << 1 for this acid. Which of the following statements is true?

Select one:

### Explanation

Weak acids have small Ka and will not fully dissociate so there should be very very little of the ions readily available in the solution

### Question 3

Find the pH of 0.15 M CH3COOH. Ka = 1.74 x 10-5M.

### Explanation

acetic acid is a weak acid

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

1.74e-5= x^2/(.15)

x=0.0016155

pH=-log(x)= 2.79

### Question 4

Find the pH of 0.161 M phenol, C6H5OH. The H bonded to the O is acidic, that is,

C6H5OH(aq) + H2O(l) ↔ H3O+(aq) + C6H5O-(aq). Ka = 1.0 x 10-10 M.

Use the same procedure as used in the last problem.

### Explanation

1e-10=x^2/.161

x=0.000004012

pH=-log(x)= 5.3965

### Question 5

Calculate the approximate [OH-] and [NH4+] in a 0.15 M ammonia solution, NH3(aq).

NH3(aq) + H2O(l) ↔ OH-(aq) + NH4+(aq). Kb = 1.75 x 10-5M.

Use the same procedure as used in the last 2 problems. Details for those who want a little extra help:

### Question 6

Calculate the pH of 0.029 M ammonia.

NH3(aq) + H2O(l) ↔ OH-(aq) + NH4+(aq) Kb = 1.75 x 10-5

### Explanation

1.75e-5 = x^2/0.029

x=0.00071239

pOH= -log(x)=3.1472

14-pOH= 10.85

### Question 7

Which of the following compounds are Bronsted-Lowry bases?

Bronsted-Lowry acids and bases

Select one or more:

### Question 8

Determine the conjugate base for the acid HF in ammonia.

HF + NH3 → NH4+ + F-

Select one:

### Question 9

Indicate whether the ion is acidic, basic, or neutral by writing A, B, or N, respectively.

F- (HF is not one of the 6 strong acids)

### Question 10

Cl-       (Is HCl one of the 6 strong acids?)

HNO3

NO3-

### Question 13

CH3COO- (the acetate ion)

### Question 14

HCOOH (formic acid)

### Question 15

HCOO- (formate ion)

### Question 16

Indicate whether the species is acidic, basic, or neutral by writing A, B, or N, respectively.

Ca2+

K+

### Question 18

CH3NH2 (like NH3 but one of the H is replaced with CH3)

CH3NH3+

### Question 20

Match strongest to weakest acid.

 acetic Choose...2nd strongest acidstrongest acid4th strongest acid3rd strongest acidweakest acid hydrocyanic Choose...2nd strongest acidstrongest acid4th strongest acid3rd strongest acidweakest acid hydrofluoric Choose...2nd strongest acidstrongest acid4th strongest acid3rd strongest acidweakest acid iodic Choose...2nd strongest acidstrongest acid4th strongest acid3rd strongest acidweakest acid phenol Choose...2nd strongest acidstrongest acid4th strongest acid3rd strongest acidweakest acid

### Explanation

Remember the larger Ka, the stronger the acid.

### Question 21

Match strongest to weakest conjugate base.

CH3COO-
CN-
F-
IO3-
C6H5O-

### Explanation

Remember the weaker the acid, the stronger the conjugate base.

### Question 22

Which of the following solutions are buffers?

Buffer solutions

Select one or more:

### Explanation

Remember, to prepare a buffer solution you must use a weak acid and its conjugate base or a weak base and its conjugate acid!

### Question 23

What is the pKa for phenol? Ka = 1.0 x 10-10.

Buffer calculation

### Explanation

pKa = -log(Ka)= -log(10e-10)

### Question 24

What is the pH of a buffer solution of phenol and its conjugate base. [C6H5OH] = 0.41 M and [C6H5O]- = 0.78 M.

### Explanation

pH= pKa +log ( CB/A)

=10 + log(.78/.41)

=10.279