Question

What will be the pH of 1.0 M ammonium formate solution, if Ka = 1 *10^-4 acid Kb = 1 *10^-5:

Answer 1

Answer: pH pf ammonium formate solution will be 6.5

Explanation: Ammonium formate is a salt of weak acid (formic acid) and strong base (ammonia). We can calculate pH by using the formula:

$pH=\frac{1}{2}(pK_w+pK_a-pK_b)$

We are given values of $K_a\text{ and }K_b$

$K_a=1\times10^{-4}\\K_b=1\times10^{-5}$

Relation between $pK_a\text{ and }K_a$ is

$pK_a=-logK_a$

$pK_a=-log(0.0004)$

$pK_a=4$

similarly, $pK_b=5$

and $pK_w=14$  (known)

Putting values in equation 1, we get

$pH=\frac{1}{2}(14+4-5)$

pH = 6.5

Answer 2

Answer:

6.5

Explanation:

ph = 7 + 0.5pka - 0.5pkb