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CGB IGCSE Chemistry
Practice Problems Quantitative Chemistry
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Practice Problems
Answers to Practice Problems

Quantitative Chemistry
1.  Find the relative Atomic Mass (Ar) for the following elements.
  • O
  • C
  • S
  • P
  • Mg
  • Fe

2.  Find the relative formula mass (Mr) for the following compounds.

  • H2O
  • H2SO4
  • CaCO3
  • MgO
  • Na2CO3
  • Mg(NO3)2
  • FeCl3
  • H3PO4
  • C6H8O7
  • KNO3

2.  Find the percentage of oxygen in the following compounds.  Which compound has the greatest percentage of oxygen? 

  • CaO
  • HNO3
  • C2H5OH
  • C6H12O

3.  Find the percentage of carbon in the following compounds.  Which compound has the least percentage of carbon?

  • CO2
  • C2H2
  • MgCO3

4. Sebastian needs to make 20 g of ZnCl2.  He knows he can make ZnCl2 by reacting Zn with HCl acid.

  • Balance the equation

              Zn + HCl --> ZnCl2 + H2

  • Determine the relative atomic masses and the relative formula masses for the reactants and the products.
  • Determine the ratio of Zn to ZnCl2
  • Determine the ratio of HCl to ZnCl2
  • Determine how much Zn and HCl you need to form 20 g of ZnCl2.

5.  Jane wants to make 100 g of Hg.  To do this she is going to heat HgO to form Hg and O2.

  • What type of reaction is this?
  • Balance the equation

               HgO --> Hg + O2

  • Determine the relative formula and relative atomic masses of the reactants and of the products.
  • Determine the ratio of HgO to Hg
  • Determine how much HgO Jane needs to heat to form 100g of Hg.

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