50 gram of calcium carbonate was completely burnt in air. What is the weight (in grams) of the residue:
Correct answer: A. 28.
- A. 28.
- B. 46.
- C. 2.8.
- D. 4.8.
Explanation
When calcium carbonate is burnt in air it decomes to calciumoxide and carbondioxide as follows: CaCO3 (s) CaO + CO2 Molar mass of CaCO3=100.1gmol No. of moles = mass in grams /molar mass =50/100.1 =0.5 moles According to balanced euation one mole of calcium carbonate produces 1 mole of calciumoxide and carbondioxide similarly 0.5 moles of calcium carbonate will produce 0.5 moles of CaO and CO2 so, Molar mass of CaO=56g/mol Mass in grams of residue= 0.5*56g/mol = 28g.
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