Question

Rank the following compounds from greatest to least conductivity: 0.05M CH3COOH, 0.05M NaCl, and 0.05M sucrose. b) explain the ranking. c) Why do we clean glassware with DI water instead of tap?

Answer 1

a) 0.05 M NaCl > 0.05 M CH₃COOH > 0.05 M Sucrose

b) Conductivity of substance depends on number of ions present in the solution.

i e Conductivity Number of ions present in the solution.

NaCl is ionic compound. It dissociates completely when dissolved in water.

NaCl (s) Na ⁺ (aq) + Cl ^- (aq)

one mole of NaCl produces two moles of ions.

Therefore, 0.05 mole NaCl will produce 0.10 mole ions.

Acetic acid is weak acid. It dissociates partially when dissolved in water.

Sucrose is molecular compound. It do not dissociate into ions. Therefore, it does not conduct electricity.

Therefore, order of conductivity is 0.05 M NaCl > 0.05 M CH₃COOH > 0.05 M Sucrose.

C)

Tap water contain metal ions , carbonates , bicarbonates and chlorides. Due to these ions, tap water conductivity is high as compared to distilled water.

If glassware were washed by distilled water , there is no chance for error in conductivity measurement. But if we use tap water , there is chance for error in conductivity measurement as tap water contain ions.

Hence, to minimize error in conductivity measurement , we use distilled water to wash glassware.