5.3.1.3 Mass changes when a reactant or product is a gas Quiz: AQA Combined Science, Unit 10

The 20 questions

1. Why does the measured mass increase when magnesium burns in open air?

   • Water evaporated
   • Gas escaped
   • Carbon lost
   • Oxygen added

2. During thermal decomposition of copper carbonate in an open tube, why does solid mass drop?

   • Copper was lost
   • Carbon dioxide escaped
   • Oxygen was absorbed
   • Water was added

3. What is the solid product when a metal carbonate decomposes on heating?

   • The metal oxide
   • Pure carbon
   • Carbon dioxide gas
   • The metal chloride

4. 50 g of calcium carbonate is heated in an open crucible: CaCO3 -> CaO + CO2. What mass of solid calcium oxide remains? (Mr CaCO3 = 100, CaO = 56)

   • 28 g
   • 50 g
   • 44 g
   • 22 g

5. In the same heating of 50 g of calcium carbonate in an open crucible, what mass of carbon dioxide escapes?

   • 44 g
   • 28 g
   • 22 g
   • 6 g

6. 6.0 g of magnesium burns completely in air to form magnesium oxide (Mr 40). What mass of MgO forms?

   • 6.0 g
   • 10.0 g
   • 16.0 g
   • 4.0 g

7. 6.0 g of magnesium forms 10.0 g of magnesium oxide in air. What mass of oxygen combined with it?

   • 10.0 g
   • 16.0 g
   • 4.0 g
   • 6.0 g

8. 84 g of magnesium carbonate (Mr 84) decomposes completely to magnesium oxide (Mr 40) and CO2. What mass of CO2 is released?

   • 40 g
   • 44 g
   • 124 g
   • 84 g

9. Why does heating copper carbonate in an open test tube cause the mass to decrease?

   • Atoms were completely destroyed
   • Solid turned into a liquid
   • Gas escaped into air
   • Heat added extra buoyancy

10. Why does a closed reaction flask show no change in total mass?

    • Energy conserved
    • Atoms destroyed
    • Gas escaped
    • Closed system

11. Using the particle model, why does mass drop when gas forms in an open container?

    • Molecules become smaller
    • Gas particles leave
    • Particles shrink
    • Atoms are destroyed

12. Which reaction type typically shows a mass increase in an open container?

    • Metal oxidation
    • Thermal cracking
    • Neutralisation
    • Thermal decomposition

13. What defines a non-enclosed chemical system?

    • Matter can escape
    • Temperature is constant
    • Energy is trapped
    • No mass changes

14. 10.8 g of aluminium reacts with oxygen and 20.4 g of aluminium oxide forms. What mass of oxygen combined?

    • 9.6 g
    • 20.4 g
    • 5.4 g
    • 10.8 g

15. 12.4 g of copper carbonate is heated in an open tube and the solid mass falls to 8.0 g. What mass of carbon dioxide was released? (Mr CuCO3 = 124, CuO = 80)

    • 20.4 g
    • 12.4 g
    • 4.4 g
    • 8.0 g

16. 25 g of zinc carbonate (Mr 125) decomposes in an open container to zinc oxide (Mr 81). What mass of solid zinc oxide remains?

    • 8.8 g
    • 16.2 g
    • 20.2 g
    • 25.0 g

17. Why might heating magnesium in an open crucible yield less mass than expected?

    • Water is added
    • Pressure drops
    • Oxygen is lost
    • Smoke escapes

18. Which equation involves a gaseous product escaping from an open container?

    • NaOH + HCl -> NaCl + H2O
    • 2Mg + O2 -> 2MgO
    • CaCO3 -> CaO + CO2
    • C + O2 -> CO2

19. How does a metal oxide's mass compare to the original metal?

    • Equal
    • Smaller
    • Greater
    • Zero

20. What happens to the measured mass when sodium carbonate reacts with acid in an open beaker?

    • Doubles
    • Stays constant
    • Increases
    • Decreases

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