# Alevel chemistry question help

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#1
Zinc chloride can be prepared in the laboratory by the reaction between zinc and hydrogen chloride gas. An impure sample of zinc powder with a mass of 5.68g was reacted with hydrogen chloride gas until the reaction was complete. The zinc chloride produced had a mass of 10.7g. Calculate the percentage purity of the zinc metal.

I got a value of 87.5 from working out the moles of HCl then subtracting it from the total vale of ZnHCl produced divided by the total times a hundred
0
3 years ago
#2
(Original post by Me123456789)
Zinc chloride can be prepared in the laboratory by the reaction between zinc and hydrogen chloride gas. An impure sample of zinc powder with a mass of 5.68g was reacted with hydrogen chloride gas until the reaction was complete. The zinc chloride produced had a mass of 10.7g. Calculate the percentage purity of the zinc metal.

I got a value of 87.5 from working out the moles of HCl then subtracting it from the total vale of ZnHCl produced divided by the total times a hundred
You know that the balanced equation between reacting zinc metal and hydrogen chloride gas is:

Zn + 2HCl ---> ZnCl2 + H2

1) Now calculate the moles of zinc chloride produced (use mol = mass/mr)

2) Then look up at the molar ratio between zinc chloride and zinc metal.

(By comparing the stoichiometric ratio you should be able to find the actual moles of zinc metal that reacted)

3) Given that you now know the moles of zinc metal, find the mass of zinc by multiplying Ar and mol value of zinc

4) Once you have done that, the percentage purity of zinc metal can be found, using x/y *100 = % purity

Where 'x' in this case is the actual mass of zinc metal obtained in step 3 and 'y' is the impure zinc mass i.e. 5.68 g.
2
1 year ago
#3
This explained it so well thankss
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