Download - Stoichiometry
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STOICHIOMETRY
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Example 1:2Mg + O2 2MgO
0.025 mol 0.025 mol
What is the mass of the oxide formed if 0.6 g of magnesium is burnt in excess oxygen?
Number of moles of Mg = =0.025 mol
0.6
24
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Stoichiometry:
From the equation :2 moles of magnesium, Mg produce 2 moles of magnesium oxide, MgO
From the calculation :0.025 mole of magnesium, Mg produce 0.025 mole of magnesium oxide, MgO
Therefore, mass of MgO Mass = 0.025 x 40 = 1.0 g
n =_mass___ molar mass
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Example 2:CaCO3 + 2HCl CaCl2 + H2O + CO2
0.05 mol 0.05 mol
What is the volume of carbon dioxide released when 5 g of calcium carbonate reacts with hydrochloric acid at room condition?
Number of moles of CaCO3 = =
5.0
1000.05 mol
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Stoichiometry:
From the equation :1 mole of calcium carbonate, CaCO3 produce
1 mole of carbon dioxide, CO2
From the calculation :0.05 mole of calcium carbonate, CaCO3 produce0.05 mole of carbon dioxide, CO2
Therefore, volume of CO2: Volume = 0.05 x 24
= 1.2 dm¯³
n =_volume__ molar volume
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Example 3:5.0 g of hydrated copper(II) sulphate, CuSO4.5H2O is heated to remove its water vapour. Calculate the mass of water vapour removed.
CuSO4.5H2O CuSO4 + 5H2O
Number of moles of CuSO4.5H2O = =
6
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Stoichiometry:
From the equation :
..................................................................................
..................................................................................
..................................................................................
.................................From the calculation :
………………………………………………………………………………………………………………………………………………………………………………………………………………
Therefore, mass of water vapour : Mass == 7
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Example 4
3.1 g of sodium oxide is formed when the sodium metal is burnt completely in oxygen at STP. Calculate the volume used.
4Na + O2 2Na2O
Number of moles of Na2O = =
8
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Stoichiometry:
From the equation :
………………………………………………………………………………………………………………………………………………………………………………
From the calculation :.………..……………………………………………………………………………………………………………………………………………………………………Therefore, volume of oxygen:
9