Conservation of Mass and Balanced Equations Quiz
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5 questions, one answer each
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1. What does the law of conservation of mass state?
- A. Mass can be created but not destroyed in a reaction
- B. No atoms are lost or made during a chemical reaction, so mass of products equals mass of reactants
- C. Gases have no mass
- D. Mass always increases during a chemical reaction
2. Which part of a balanced equation can be changed to balance it?
- A. The subscripts within formulae
- B. The multipliers placed in front of formulae
- C. The state symbols
- D. The element symbols
3. A student heats calcium carbonate in an open test tube and finds the solid remaining weighs less than the starting carbonate. What best explains this?
- A. Mass has been destroyed, breaking the law of conservation of mass
- B. Carbon dioxide gas has escaped into the air, so the measured mass of the solid decreases even though total mass is conserved
- C. The balance used was faulty
- D. Calcium carbonate has no measurable mass when heated
4. Magnesium is burned in air and the solid product has a greater mass than the original magnesium. Why?
- A. The law of conservation of mass has been broken
- B. Oxygen from the air has combined with the magnesium, adding mass to the solid product
- C. Magnesium gains electrons from the air, which have significant mass
- D. The balance was reading incorrectly
5. A reaction produces 4.4 g of CO2 (Mr = 44) and 1.8 g of H2O (Mr = 18) from the combustion of a hydrocarbon. Using moles, what is the simplest whole number mole ratio of CO2 to H2O produced?
- A. 1:1
- B. 1:2
- C. 1:1 (0.1 mol : 0.1 mol)
- D. 2:1