NPS International School
Name: _____________________
Subject: Chemistry
Date: _________________
Grade:
IX IGCSE
Metal Extraction and Stoichiometry
1
In the water treatment process, hexafluorosicilic acid, H2SiF6, is used as a disinfectant
to remove unpleasant taste and odour. One of the methods of producing
hexafluorosicilic acid, is shown by the unbalanced equation below.
Na2SiO3 (s) + HF (aq) → H2SiF6 (aq) + NaF (aq) + H2O (l)
(a)
(b)
(c)
(d)
(e)
(f)
2
Write down the balanced chemical equation of the reaction.
Calculate the percentage by mass of silicon in hexafluorosicilic acid.
The aqueous solution of the reactant HF, is formed by dissolving 1.80 dm3 of
gas in 50.0 cm3 of water. Calculate the concentration of HF in
(i) mol/dm3
(ii) g/dm3
How many moles of HF are needed to react with 0.300 mol of Na2SiO3?
Calculate the mass of NaF formed when 0.500 mol of HF reacts with excess
Na2SiO3?
Calculate the mass of Na2SiO3 that can react with 0.800 g of HF?
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[3]
The Ostwald process is used to manufacture nitric acid in a multi-step procedure. In
the first step, ammonia gas is oxidized to form nitrogen monoxide and water vapour.
(a)
(b)
(c)
Write a balanced chemical equation for the first step.
1.0 mol of ammonia is allowed to react with 1.0 mol of oxygen.
(i) Identify the limiting reactant?
(ii) How many moles of nitrogen monoxide are formed?
(iii) Calculate the volume of water vapour formed?
In the final step, nitrogen dioxide is mixed with air and then dissolved in water
to produce a solution of nitric acid.
(i)
a 2balanced
4NO2 Write
(g) + O
(g) + 2Hchemical
4HNO3 for
(aq)the final step.
2O (l) →equation
(ii) What is the percentage by mass of NO2 in HNO3?
(iii) Calculate the volume of oxygen gas, measured at room temperature and
pressure, needed to react with 240 dm3 of nitrogen dioxide.
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NPS International School
100 cm of 2.0 mol/dm sulfuric acid was mixed with 50 cm3 of 1.0 mol/dm3 sulfuric
acid.
(a) What is the total volume of the resulting mixture
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(b) Calculate the total number of moles of acid in the resulting mixture.
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(c) Hence, calculate the concentration of the resulting mixture.
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3
In the blast furnace extraction of iron, raw materials, haematite, coke and substance D
are added from the top. The haematite ore is mixed with carbon monoxide at high
temperatures to extract elemental iron, which can be tapped off near the bottom of the
furnace, together with substance G.
(a)
(b)
(c)
(d)
(e)
(f)
Name substance D.
Explain the purpose of adding substance D.
Write down the balanced chemical equation of the reaction between haematite
ore is mixed with carbon monoxide
A mass of 16 kg of iron ore is added to the furnace and is made to react with
1200 dm3 of carbon monoxide.
(i) Identify the excess reactant.
(ii) Calculate the volume of carbon dioxide formed.
(iii) At the end of the process, the mass of iron collected was 1.35 kg. Calculate
the percentage yield of iron.
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Give the chemical name of substance G.
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Another metal, lead can also be extracted from an ore, which contains mainly
lead(II) sulfide, by a 2-step process.
Step 1 : The ore is first heated in air to produce lead(II) oxide and sulfur dioxide.
Step 2 : The lead(II) oxide produced is then reduced with carbon.
(i) Write a balanced chemical equation for each of the 2 steps.
(ii) How does your equation in step 2 show that lead(II) oxide is reduced?
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