✔ 最佳答案
1.
Add separately each of the two substances to dilute sodium hydroxide solution in a test tube. Warm each mixture.
Ammonium chloride : A colourless gas is given off which turns moist red litmus paper to blue.
Potassium chloride : No observable change.
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2.
If the substances are in solid state, dissolve separately each of the four substances in distilled water to give a solution.
Put separately 2 cm³ of each of the four solutions in a test tube, and add dilute sodium sulphate solution.
Only Pb(NO3)2 solutions gives a white precipitate.
The other three solutions give no observable change.
Put separately 2 cm³ of each of the rest three solutions in a test tube, and add dilute sodium hydroxide solution, firstly dropwise and then in excess.
NaCl solution gives no observable change.
ZnCl2 and Mg(NO3)2 solutions give white precipitates.
For ZnCl2 solution, the precipitate re-dissolves to give a colourless solution.
For Mg(NO3)2 solution, the precipitate remains unchanged when excess sodium hydroxide solution is added.