GRADE 9 INTEGRATED SCIENCE SUMMARY AND EXERCISE
CHEMISTRY MOLE AND CHEMICAL EQUATIONS
Name : ________________
I.
Date : _______________
CALCULATING MOLAR MASS FROM SINGLE COMPOUND
𝑚𝑎𝑠𝑠 = 𝑛𝑜. 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠 𝑥 𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠
Mass
No. of
Molar
𝑛𝑜. 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠 =
Moles
Mass
𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 =
𝑀𝑎𝑠𝑠
𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠
𝑚𝑎𝑠𝑠
𝑛𝑜.𝑜𝑓 𝑚𝑜𝑙𝑒𝑠
Example as exercise :
1. How many moles are there in 60g of sodium hydroxide?
Step 1 : calculate the molar mass of sodium hydroxide (NaOH)
Step 2 : calculate the moles by following the formula.
2. What is mass of 0.8 moles of copper (ii) sulfate crystals?
Step 1 : calculate the molar mass of copper(ii) sulfate crystals ( this is
a solution, therefore there are molecules of copper sulfate and water)
CuSO4 + 5H2O
Step 2 : calculate the mass by following the formula.
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3. Find the mass of 3 moles of ethanol, C2H5OH.
Step 1 :
Step 2 :
4. How many moles of molecules are there in:
a. 18 grams of hydrogen
Step 1 :
Step 2 :
b. 54 grams of water?
Step 1 :
Step 2 :
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5. How many moles of Fe2O3 are there in 32 kg of iron(III) oxide? (1kg=
1000 g.)
Step 1 :
Step 2 :
II.
CALCULATING MOLAR MASS FROM A CHEMICAL EQUATION
 You need to consider the conservation of mass ( the mass of reactants
are equal to the mass of the product.)
Example as exercise :
1. When iron react with sulfur.
o Write the chemical equation for the reaction and write each of
their relative atomic mass. (the result will be the ratio of the
reaction)
o If 5g of sulfur react with 5.6 of iron. How many gram of sulfur will
be unreacted?
o How many gram of iron oxide produced when 19.6g of iron reacts
completely with sulfur?
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2. The reaction between magnesium and oxygen is:
2Mg (s) + O2 (g) → 2MgO (s)
a. How many moles of magnesium atoms react with 1 mole of oxygen
molecules?
b. The Ar values are: Mg = 24, O = 16.
i.
What is the ratio of the equation ?
ii.
How many grams of oxygen react with:
- 48 g of magnesium?
- 12 g of magnesium?
3. Copper(II) carbonate breaks down on heating, like this:
CuCO3 (s) → CuO (s) + CO2 (g)
a. Find the mass of 1 mole of each substance taking part in the reaction.
(Ar : Cu = 64, C = 12, O = 16.)
b. Ratio for the reaction
c. When 31 g of copper(II) carbonate is used:
i.
How many grams of carbon dioxide form?
ii.
What mass of solid remains after heating?
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4. Mercury(II) oxide breaks down on heating:
2HgO (s) → 2Hg (l) + O2 (g)
a. Calculate the mass of 1 mole of mercury(II) oxide. (Ar : O2 : 16,
Hg = 201)
b. Write the ratio for the reaction
c. How much mercury and oxygen could be obtained from 21.7 g of
mercury(II) oxide?
5. 27 gram of aluminium burns in chlorine to form 133.5 gram of aluminium
chloride (Ar : Al = 27. Cl= 35.5)
a. Write balance equation for this reaction.
b. What is the ratio for the reaction?
c. What mass of chlorine is present in 133.4g or aluminium chloride?
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