Question

When mixed together, all of the following pairs can form buffers EXCEPT a. H3PO4 and NaH2PO4. b. HCl and NaCH3CO2. c. CH3CO2H and NaOH. d. NaI and NaOH. e. NaH2PO4 and Na2HPO4

Answer 1

a. H3PO4 and NaH2PO4.

H3PO4 is weak acid and H2PO4- is conjugate base.

So, this will form buffer

b. HCl and NaCH3CO2.

CH3CO2- is conjugate base of CH3COOH.

CH3COO- can react with HCl and form CH3COOH if HCl is in less amount.

Then final solution will be CH3COOH and CH3COONa

So, this will form buffer

c. CH3CO2H and NaOH.

CH3CO2H can react with NaOH and form CH3COONa

Then final solution will be CH3COOH and CH3COONa

So, this will form buffer

d. NaI and NaOH.

NaI is salt and NaOH is base.

They will not form buffer

e. NaH2PO4 and Na2HPO4

H2PO4- is acid and HPO42- is its conjugate base.

So, this will form buffer

Answer: d