Question

Cu (II) sulfate exists as a hydrate. It has many practical uses including use as a fungicide and pesticide. When mixed with chromium and arsenic it forms the wood preservative called CCA. CCA was used in pressure treated wood to protect wood from rotting due to insects and microbial agents. Because CCA treated wood contains toxic heavy metals, its use has been discontinued for home use and children’s play sets. 1. A chemist is given a sample of the CuSO4 hydrate and asked to determine the empirical formula of it. The original sample weighed 42.75 g. After heating to remove the waters of hydration, the sample weighed 27.38 g. Determine the formula for this hydrate.

Answer 1

Answer:

CuSO4.5H2O

Explanation:

Recall that;

mass of anhydrous salt/ molar mass of anhydrous salt  = mass of hydrated salt/molar mass of hydrated salt

mass of anhydrous salt =  27.38 g

mass of hydrated salt = 42.75 g

molar mass of anhydrous salt = 160 g/mol

molar mass of hydrated salt = 160 + 18x

27.38 g/160 g/mol = 42.75 g/160 + 18x

27.38 (160 + 18x) =160 * 42.75

4380.8 + 492.84x = 6840

492.84x = 6840 - 4380.8

492.84x = 2459.2

x = 2459.2/492.84

x = 5

Hence the formula of the hydrate is; CuSO4.5H2O