Few chemistry tasks that I don't understand at all

[Vichy]

1. Here are few chemistry tasks,I need your help!



2.
4.120g 15% BaCl2 solution is added to 800ml 0,2mol/L Iron (III) sulphate solution.How many g of precipitate formed?Which and how much of material did not react?
5. 5g of solution,which consists of copper and zinc,is affected by solution of H2SO4. 0,05 mol of gas formed.Calculate W% of copper in the solution.
6.How many g of Fe(sawdust of Fe) will react when added to 50ml 20% HCl solution which has density of 1,1g/cm3 ?
7.What density of 20% HCl(density-1,1g/cm3) solution is needed to dissolve 30g Iron (III) oxide,which has 20% of addition?
8.How many g of salt will form,if 20g of Fe which has 10% of addition,will be affected by solution of H2SO4?



3. As I mentioned I can't understand this at all so I didn't make any attempts on solving these tasks.If you see any grammar mistakes-I'm sorry for that,English isn't my native language.

 

[Borek]

Each time you need to start with reaction equation(s).