Question

Which of the following pairs of substances can be used to make a buffer system? Choose all that apply. a) H2CO3 and Na2CO3 b) H2C2O4 and Na2C2O4 c) NH4Cl and NH3 d) H3PO4 and NaH2PO4 e) H3PO4 and Na2HPO4

Answer 1

acidic buffer is formed by weak acid and salt of weak acid

basic buffer is formed by weak base and salt of weak base

a)

H2CO3 is acid

Its conjugate base would be NaHCO3 which is not present

So, it can’t be a buffer

b)

H2C2O4 is acid

Its conjugate base would be NaHC2O4 which is not present

So, it can’t be a buffer

c)

NH3 is base

Its conjugate acid would be NH4Cl which is present

So, it is a basic buffer

d)

H3PO4 is acid

Its conjugate base would be NaH2PO4 which is present

So, it is an acidic buffer

e)

H3PO4 is acid

Its conjugate base would be NaH2PO4 which is not present

So, it can’t be a buffer

Answer: c and d