WAEC Chemistry 2013 Objective — Question 21
Question 21 of 50 from the West African Examinations Council (WAEC) Chemistry 2013 Objective paper, with the correct answer and a full explanation.
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The percentage by mass of calcium in Ca(OCl)2 is [Ca = 40.0; Cl = 35.5; O = 16.0]
- A. 28.0%Correct
- B. 31.6%
- C. 43.8%
- D. 44.5%
Explanation
Molar mass of Ca(OCl)2 = 40+2(16+35.5) = 40+2(51.5) = 40+103 = 143 g/mol. (% of calcium) = (Mass of Ca/Molar mass)×100% = (40/143)×100% = 28%.
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