會考急問chem mc 問題 謝幫忙

The answer is B.
This is because propanoic acid is a weak acid, which is partly ionized in water. In room temperature, less than 5% of propanoic acid is ionized in water to give H+(aq) and CH3CH2COO-(aq) ions (i.e. the concentrations of H+(aq) and CH3CH2COO-(aq) are less than 2 x 5% = 0.1 M).

A is incorrect.
This is because glucose cannot be ionized in water, and it is NOT an electrolyte.

C is incorrect.
NH4Cl is completely dissociated in water to give NH4+(aq) and Cl-(aq) ions. The solution contains 0.5 M NH4+(aq) and 0.5 M Cl-(aq) ions. C is a stronger electrolyte than B, because C contains more mobile ions.

D is incorrect.
Na2CO3 is completely dissociated in water to give Na+(aq) and CO32--(aq) ions. The solution contains 0.4 M Na+(aq) and 0.2 M CO32-(aq) ions. D is a stronger electrolyte than B, because D contains more mobile ions.

2008-03-01 12:27:43 補充：
Glucose solution is NOT an electrolyte. Therefore, it is NOT a weak electrolyte.
A weak electrolyte MUST BE an electrolyte.

應該係 a (0.1M glucose solution)
因為glucose唔係ionic，無法拆成ionic
相對地，其他三隻都係ionic solution

D 0.2M sodium carbonate solution