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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About Fundamental Concepts of Chemistry
Mole calculations connect mass, number of particles and Avogadro's number, while balanced equations provide the mole ratios used in stoichiometry. Questions cover limiting and excess reactants, theoretical yield and percentage yield, including identifying which reactant is consumed first and comparing the actual product with the maximum possible product.
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