What volume of 0.1 M HCOONa solution should be added to 50 ml of 0.05 M formic acid to produce a buffer solution of pH =4.0, p K a of formic acid =3.7 ?

Question

What volume of 0.1 M HCOONa solution should be added to 50 ml of 0.05 M formic acid to produce a buffer solution of pH =4.0, p K a of formic acid =3.7 ? (A) 50 ml (B) 40 ml (C) 30 ml (D) 60 ml

Tardigrade Admin · Accepted Answer

Let V ml of 0.1 M HCOONa be mixed to 50 ml of 0.05 M HCOOH in mixture [ HCOONa ]=(0.1 × V/(V+50)) [ HCOOH ]=(50 × 0.05/(V+50)) ∴ pH =- log K a + log ([ text Salt ]/[ text Acid ]) 4.0 =3.7+ log ((0.1 × V) /(V+50)/2.5 /(V+50)) V=50 ml

Q. What volume of 0.1MHCOONa solution should be added to 50ml of 0.05M formic acid to produce a buffer solution of pH=4.0,pKa​ of formic acid =3.7 ?

50 ml

40 ml

30 ml

60 ml

Let V ml of 0.1MHCOONa be mixed to 50ml of 0.05MHCOOH in mixture [HCOONa]=(V+50)0.1×V​ [HCOOH]=(V+50)50×0.05​ ∴pH=−logKa​+log[ Acid ][ Salt ]​ 4.0=3.7+log2.5/(V+50)(0.1×V)/(V+50)​ V=50ml

Q. What volume of $0.1 M H COON a$ solution should be added to $50 m l$ of $0.05 M$ formic acid to produce a buffer solution of $p H = 4.0, p K_{a}$ of formic acid $= 3.7$ ?