Conductance, molar conductivity and its variation with concentration
- The conductivity of centimolar solution of KCl at 25°C is 0.0210 ohm^-1 cm^-1 and the resistance of the cell containing the solution at 25°C is 60 ohm. The value of cell constant is - Answer: 4. 1.26 cm ⁻¹ Key idea: Cell constant = kappa × R . G^* = 0.0210\ Ω⁻¹mathrmcm⁻¹ × 60\ Ω = 1.26\ mathrmcm⁻¹ . Option 4. 1
- The molar conductivity of 0.007 M acetic acid is 20 S cm^2 mol^-1. What is the dissociation constant of acetic acid ? Choose the correct option.^°_H^+ = 350 S cm^2 mol^-1, ^°_CH_3COO^- = 50 S cm^2 mol^-1 Answer: 3. 1.75×10⁻⁵ mol L ⁻¹ Key idea: α=Lambda_m/Lambda^°_m , and K_a=Cα²/1-α≈ Cα² . Lambda^°=350+50=400 ; α=20/400=0.05 . K_a≈0.007×(0.05... 1
- Ionic mobility of which of the following alkali metal ions is lowest when aqueous solution of their salts are put under an electric field ? Answer: 3. Li Key idea: in aqueous solution ionic mobility falls with greater hydration, and smaller ions hydrate more. Hydrated size order... 1
- The molar conductivity of a [obscured] solution of AgNO_3 with electrolytic conductivity of 5.76×10^-3 S cm^-1 at 298 K is Answer: 1. 11.52 S cm ² /mol Key idea: molar conductivity Lambda_m=kappa×1000/M (S cm ² mol ⁻¹ , kappa in S cm ⁻¹ , M in mol/L). Lambda_m=fr... 1