Question

Calculate the percent water in ZnSO4.7 H20. Show your work.

Answer 1

Answer:

43.8%

Explanation:

Find the sum of the relative atomic mass of all the elements constituting the compound, which is known as the relative formula mass;

$M_{r} = Relative \ formula \ mass \\\\M_{r} \ of \ ZnSO_{4} = 65.4 + 32.1 + 4(16) \\\\M_{r} \ of \ ZnSO_{4} = 97.5 + 64 \\\\M_{r} \ of \ ZnSO_{4} = 161.5 \\\\M_{r} \ of \ H_{2}O = 18 \\\\M_{r} \ of \ ZnSO_{4}.7H_{2}O = 161.5 + 7(18) \\\\M_{r} \ of \ ZnSO_{4}.7H_{2}O = 287.5$

Then, divide the relative formula mass of all the water by that of the whole compound

w = % water

$w = \frac{7(18)}{287.5} * 100 \\\\w = 0.43826... * 100\\\\w = 43.826...$

w = 43.8%