The resistance of a 0.10 M weak acid HA in a conductivity cell is 2.0xx10^(3)ohm. The cell constat of the cell is 0.78 cm^(-1) and wedge_(0) of the acid is 390 S cm^(2)mol^(-1). Consider the following statements: 1. pH of the acid solution=3 2. pK_(a) of the acid=5 3. Degree of dissociation the acid=0.01 Which of the statements given above are correct?

The resistance of a 0.10 M weak acid HA in a conductivity cell is 2.0x

1.	The resistance of a 0.10 M weak acid HA in a conductivity cell is 2.0xx10^(3)ohm. The cell constat of the cell is 0.78 cm^(-1) and wedge_(0) of the acid is 390 S cm^(2)mol^(-1). Consider the following statements: 1. pH of the acid solution=3 2. pK_(a) of the acid=5 3. Degree of dissociation the acid=0.01 Which of the statements given above are correct?
Answer» 1 AD 2 only 1 and 3 only 2 and 3 only 1,2 and 3 Solution :`kappa="Conductance (G)"xx"Cell CONSTANT "(G^(**))` `=(1)/(2.0xx10^(3))xx0.78=3.9xx10^(-4)Omega^(-1)cm^(-1)` `wedge=(1000kappa)/("Molarity")=(1000xx3.9xx10^(-4))/(0.10)` `=3.9" S "cm^(2)MOL^(-1)`. `thereforealpha=(wedge)/(wedge_(m))=(3.9)/(390)=10^(-2)=0.01` `HA hArr H^(+)+A^(-)` `[H^(+)]=Calpha(0.10)(10^(-2))=10^(-3)M` `K_(a)=([H^(+)][A^(-)])/([HA])=(10^(-3)xx10^(-3))/(0.1)=10^(-5)` `pK_(a)=5`.