Question

Which of the following gives a buffer solution when equal volumes of the two solutions are mixed?

(a) 0.10 MHF and 0.10 MNaOH​

(b) 0.20 MHF and 0.10 MNaOH​

(c) 0.10 MHCl and 0.20 MNaF

(d) 0.10 MHF and 0.10 MNaF

Answer 1

ANSWER :

(b) 0.20 M HF and 0.10 M NaOH​

(c) 0.10 MHCl and 0.20 M NaF

(d) 0.10 M HF and 0.10 M NaF

explanation:

(a) 0.10 MHF and 0.10 MNaOH​ : in this case total acid and base consumed so only salt is formed

(b) 0.20 MHF and 0.10 MNaOH​ :

suppose volume = 10 mL each

millimoles of HF = 10 x 0.2 = 2

millimoles of NaOH = 10 x 0.1 = 1

HF + NaOH ------------------> NaF + H2O

2            1                                 0           0

1            0                                  1            1

HF + NaF remains so it is buffer

(c) 0.10 MHCl and 0.20 MNaF :

suppose HCl volume = 10

millimoles HCl = 10 x 0.1 = 1

NaF millimoles = 0.20 x 10 = 2

NaF + HCl --------------> HF + NaCl

2          1                          0         0

1           0                          1        1

NaF + HCl remains . so it is buffer

(d) 0.10 MHF and 0.10 MNaF : this is also buffer