Practical work 1: the halogens
Answers are for parents and teachers.
1
Write the molecular and net ionic equations for NaBr solution with AgNO₃.
NaBr + AgNO₃ → AgBr↓ + NaNO₃; Ag⁺ + Br⁻ → AgBr↓
2
Mass of ZnCl₂ from 130 g (2 mol) Zn? M(ZnCl₂) = 136 g/mol.
272 g
3
Write in 3 steps a plan to prove that a seawater sample contains chloride ions (only the teacher does the experiment).
1) filter the sample; 2) add a few drops of HNO₃ and AgNO₃; 3) a white curdy AgCl precipitate that does not dissolve in nitric acid shows Cl⁻.
4
Why does adding HNO₃ to the precipitate help tell AgCl from other silver salts?
AgCl does not dissolve in acid, while salts such as silver carbonate do.
5
Why are solutions taken in small amounts in practical work?
Risk and waste are reduced, the reaction is easy to watch, material is saved.