10 g of carbon burns, giving 11.2 litres of CO₂ at STP. After combustion, the amount of unburnt carbon is:
Correct answer: C. 4 g
- A. 2.5 g
- B. 3 g
- C. 4 g
- D. 6 g
Explanation
The 11.2 L of CO₂ produced at STP corresponds to 0.5 moles. According to the reaction C + O₂ → CO₂, this means 0.5 moles of carbon reacted. The mass of carbon that is burned is 0.5 mol × 12 g/mol = 6 g. Therefore, the unburnt carbon is 10 g - 6 g = 4 g.
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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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