Question

1. Which of the following substances is a strong acid?

a. HCIO

b. HF

c. HNO₂

d. H₃PO₄

e. HNO₃

2. What is the pH of a 0.050 M solution of NaOH, a strong base?

a. 12.70

b. 7.00

c. 13.95

d. 0.05

e. 1.30

3. The K_a of acetic acid is listed at 1.8x10^-5 . What is the K_b of its conjugate base, acetate?

a. 1.8x10⁹

b. 1.8x10^-19

c. 5.56x10^-10

d. 5.56x10¹⁸

e. 1.00x10^-7

Answer 1

1. Which of the following substances is a strong acid?

a. HCIO -- weak acid

b. HF   -- weak acid

c. HNO2 -- weak acid

d. H3PO4  -- weak acid

e. HNO3 -- strong acid acid

Therefore option (e) is correct

2. What is the pH of a 0.050 M solution of NaOH, a strong base?

NaOH ---> Na⁺ + OH^-

[OH^-]=[NaOH] = 0.050 M

pOH = - log[OH^-]

= - log 0.05

= 1.3

We know that pH + pOH = 14

pH = 14 - pOH

= 14 - 1.3

= 12.70

Therefore option (a) is correct.

3. The K_a  of acetic acid is listed at 1.8x10^-5 . What is the K_b of its conjugate base, acetate?

We knon that K_a x K_b = K_w = 1.0x10^-14

So K_b = K_w / K_a

= (1.0x10^-14 )/ (1.8x10^-5 )

= 5.56x10^-10

Therfore option (c) is correct