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A mixture of CaCl2 and NaCl with a combined mass of 4.44 g is processed so that all the calcium precipitates as CaCO3, which is then heated and fully converted to CaO. The mass of CaO obtained is 1.12 g. Using atomic weights Ca = 40, Na = 23, Cl = 35.5, select the correct statement(s).

1. The mixture contains 40% NaCl by mass
2. The mixture contains 60% CaCl2 by mass
3. The mass of CaCl2 in the mixture is 2.22 g
4. The mass of CaCl2 in the mixture is 1.11 g

Correct answer: The mass of CaCl2 in the mixture is 2.22 g

Solution

From 1.12 g of CaO (molar mass 56), we get 0.02 mol Ca, hence 0.02 mol CaCl2 with mass 0.02 x 111 = 2.22 g. This leaves 4.44 - 2.22 = 2.22 g NaCl, which is 50% of the total, so CaCl2 is also 50%.

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