Question

Which of the following mixtures will be a buffer when dissolved in a liter of water?

0.1 mol Ca(OH)2 and 0.3 mol HI 0.3 mol NaCl and 0.3 mol HCl 0.4 mol NH3 and 0.4 mol HCl 0.2 mol HBr and 0.1 mol NaOH 0.2 mol H3PO4 and 0.1 mol NaOH

Answer 1

a. 0.1 mol Ca(OH)2 and 0.3 mol HI

Buffer is a combination of weak acid and its conjuage base or vice versa.

Here HI is astrong acid and Ca(OH)2 is strong base.

The combination of strong acid and base can not make a buffer .

b. 0.3 mol NaCl and 0.3 mol HCl

HCl is a strong acid. and NaCl is a neutral salt.

The combination can not make buffer

c. 0.4 mol NH3 and 0.4 mol HCl

HCl completely reaction with 0.4 mol nH3 and produce 0.4 mol NH4Cl

NH3 (aq) + HCl ----- > NH4Cl (aq)

after reaction only NH4Cl will present. so it is not a Buffer

d. 0.2 mol HBr and 0.1 mol NaOH

Both are strong acid and strong base

so they can not make buffer

e. 0.2 mol H3PO4 and 0.1 mol NaOH

so Answer is

0.2 mol H3PO4 and 0.1 mol NaOH