Question

what is the mass percent of water in calcium chloride dihydrate (cacl₂·2h₂o)?
12.25%
24.51%
27.23%
48.26%

Explanation:

Step1: Calculate molar mass of \(CaCl_2\cdot2H_2O\)

Molar mass of \(Ca = 40.08\space g/mol\), \(Cl = 35.45\space g/mol\), \(H = 1.008\space g/mol\), \(O = 16.00\space g/mol\)
Molar mass of \(CaCl_2\cdot2H_2O=40.08+(2\times35.45)+2\times(2\times1.008 + 16.00)=147.02\space g/mol\)

Step2: Calculate molar mass of water in \(CaCl_2\cdot2H_2O\)

Molar mass of \(2H_2O = 2\times(2\times1.008+16.00)=36.032\space g/mol\)

Step3: Calculate mass percent of water

Mass percent of water \(=\frac{36.032}{147.02}\times100\%\approx24.51\%\)

Answer:

24.51%