The difference samples A and B of Zinc oxide we're obtained from different sources when heated in a stream of hydrogen they were reduced to yield the following results

Question

ZnO. Mass of sample. Mass of Zn red.
Sample. A 10.0g. 8.11g
Sample B 13.2g. 10.70
Show that the figures above illustrate the law of constant composition?

Answer 1

I am sure you meant "were" and not "we're".
Also I interpret your problem to mean mass Zn produced by reduction.
Sample A.
mass ZnO = 10.0
mass Zn = 8.11
mass O = 10.0 - 8.11 = 1.89. Then
mols Zn = 8.11/65.38 = 0.124
mols O = 1.89/16 = 0.118. Reduce these to a whole number to make it easier to compare.
Zn = 0.124/0.118 = 1.05
O = 0.118/0.118 = 1.00 and this ratio is essentially 1 to 1; hence the formula of ZnO.

I won't do the sample B part but it's done the same way and you should end up with similar ratio which proves the question.
Post your work if you get stuck.

Answer 2

Am stuck I don't know how to do b

Answer 3

Mass ZnO=13.2
Mass Zn=10.70
Mass O=13.2-10.70=2.5
Mols ZnO=10.70/65.38=0.1636
Mols O =2.5/16=0.156
Zn=0.1636/0.156=1.05
O=0.156/0.156=1.00

Answer 4

What is the formula for Zno