pH of acids, bases and salts

Exercise 21

    

The $pH$ of the stomach is about $1.5$ a) Calculate the value of the ratio $\frac{[HNO_2]}{[No_2 ^ -]}$ after eating a sausage treated with sodium nitrite. The latter substance is a food additive (unfortunately carcinogenic!) It is used fo preserving meat and give it an appetizing red by interaction with hemoglobin. b) Calculate the value of of the ratio $\frac{[C_6H_5COOH]}{[C_6H_5COO ^ -]}$ after eating pickles treated with sodium benzoate. The latter substance is a preservative with antimicrobial properties.

$HNO_2, \;C_6H_5COOH $: weak acids $\frac{[HB]}{[B]}$ $=$ $\frac{[H_3O^+]}{K_a}$ a) $\frac{[HNO_2]}{[NO_2^-]}$ $=$ $\frac{10^{-1,5}}{10^{-3,30}}$ = 63.1 b) $\frac{[C_6H_5COOH]}{[C_6H_5COO^-]}$ $=$ $\frac{10^{-1,5}}{10^{-4,20}}$ = 501.187