The Language of Chemistry — Question 34

(a) Percentage composition of Calcium Chloride:

Chemical Formula of Calcium Chloride = CaCl₂

Mol. wt. of calcium chloride = At. wt. of Ca + 2(At. wt. of Cl)
= 40 + 2(35.5)
= 40 + 70
= 110

110 g of CaCl₂ contains 40 g of Calcium,

∴ 100 g of CaCl₂ will contain $\dfrac{40}{110}$ x 100 % = 36.36% of Calcium [percentage].

Similarly, 110 g of CaCl₂ will contain 70 g of Chlorine,

∴ 100 g of CaCl₂ will contain $\dfrac{70}{110}$ x 100 % = 63.64% of Chlorine.

Hence, Calcium Chloride contains 36.36% of Calcium and 63.64% of Chlorine.

(b) Percentage composition of Calcium Nitrate:

Chemical Formula of Calcium Nitrate = Ca(NO₃)₂

Mol. wt. of Calcium Nitrate = At. wt. of Ca + 2[At. wt. of N] + 6[At. wt. of O]
= 40 + 2(14) + 6(16)
= 40 + 28 + 96
= 164

164 g of Ca(NO₃)₂ contains 40 g of Calcium,

∴ 100 g of Ca(NO₃)₂ will contain $\dfrac{40}{164}$ x 100 % = 24.39% of Calcium.

Similarly, 164 g of Ca(NO₃)₂ will contain 28 g of Nitrogen,

∴ 100 g of Ca(NO₃)₂ will contain $\dfrac{28}{164}$ x 100 % = 17.07% of Nitrogen.

Similarly, 164 g of Ca(NO₃)₂ will contain 96 g of Oxygen,

∴ 100 g of Ca(NO₃)₂ will contain $\dfrac{96}{164}$ x 100 % = 58.54% of Oxygen.

Hence, Calcium Nitrate contains 24.39% of Calcium, 17.07% of Nitrogen and 58.54% of Oxygen.