Reacting Masses Quiz
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5 questions, one answer each
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1. What does the law of conservation of mass state about a chemical reaction?
- A. Mass is always lost during a reaction
- B. The total mass of products always equals the total mass of reactants
- C. Mass increases if the reaction is exothermic
- D. Mass can only be conserved in reactions involving gases
2. What is the correct order of steps for calculating a reacting mass from a balanced equation?
- A. Convert to moles, apply mole ratio, convert back to mass
- B. Apply mole ratio to masses directly
- C. Convert to mass, apply mole ratio, convert to moles
- D. Multiply masses of reactants together
3. In the reaction N2 + 3H2 → 2NH3, how many moles of hydrogen are needed to react completely with 2 moles of nitrogen?
- A. 2 mol
- B. 3 mol
- C. 6 mol
- D. 1 mol
4. Calculate the mass of carbon dioxide produced when 10 g of calcium carbonate decomposes: CaCO3 → CaO + CO2 (Ar: Ca = 40, C = 12, O = 16).
- A. 4.4 g
- B. 44 g
- C. 10 g
- D. 1.0 g
5. A student calculates a theoretical yield of 5.0 g of product but only obtains 4.2 g in the experiment. Which of the following is the most likely explanation?
- A. Extra atoms were created during the reaction
- B. Some product was lost during separation from the reaction mixture
- C. The balanced equation used was incorrect and cannot be trusted
- D. The law of conservation of mass does not apply to this reaction