11. Which of the following will produce a buffer solution when mixed in equal volumes?

(1) 0.1 mol dm-3 NH4OH and 0.1 mol dm-3 HCl

(2) 0.05 mol dm-3 NH4OH and 0.1 mol dm-3 HCl

(3) 0.1 mol dm-3 NH4OH and 0.05 mol dm-3 HCl

(4) 0.1 mol dm-3 CH3COONa and 0.1 mol dm-3 NaOH

HINT-Weak base and its salt with strong acid forms buffer when both are present together in solution
 
EXPLAINATION(3) When the concentration of NH4OH (weak base) is higher than the strong acid (HCl), a mixture of weak base and its conjugate acid is obtained, which acts as basic buffer
InitiallyAfter reaction NH4OH0.1 M0.05 M+HCl0.05M0NH4Cl00.05 M+H2O