Amount of Substance Questions
1.
Under suitable conditions magnesium will react with dilute nitric acid according to the
following equation.
Mg(s) + 2HNO3(aq) →Mg(NO3)2(aq) + H2(g)
A 0.0732 g sample of magnesium was added to 36.4 cm3 of 0.265 mol dm–3 nitric acid.
The acid was in excess.
(a)
(i)
Calculate the amount, in moles, of magnesium in the 0.0732 g sample.
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(1)
(ii)
Hence calculate the amount, in moles, of nitric acid needed to react
completely with this sample of magnesium.
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(1)
(iii)
Calculate the amount, in moles, of nitric acid originally added to this sample
of magnesium.
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(1)
(iv)
Hence calculate the amount, in moles, of nitric acid that remains unreacted.
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(1)
(b)
Concentrated nitric acid reacts with magnesium to form an oxide of nitrogen
which contains 30.4% by mass of nitrogen.
Calculate the empirical formula of this oxide of nitrogen. Show your working.
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Total 7 Marks
2.
(a)
(3)
Define the term relative atomic mass.
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(2)
(b)
How would you calculate the mass of one mole of atoms from the mass of a single
atom?
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(1)
(c)
Sodium hydride reacts with water according to the following equation.
NaH(s) + H2O(l)  NaOH(aq) + H2(g)
A 1.00 g sample of sodium hydride was added to water and the resulting solution
was diluted to a volume of exactly 250 cm3.
(i)
Calculate the concentration, in mol dm–3, of the sodium hydroxide solution
formed.
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(ii)
Calculate the volume of hydrogen gas evolved from the above reaction
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(iii)
Calculate the volume of 0.112 mol dm-3 hydrochloric acid which would
react exactly with a 25.0 cm3 sample of the sodium hydroxide solution.
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(8)
(Total 8 marks)
3.
(a)
Titanium(IV) chloride reacted with water as shown in the following equation.
TiCl4(l) + 2H2O(l)  4HCl(aq) + TiO2(s)
The reaction produced 200 cm3 of a 1.20 mol dm-3 solution of hydrochloric acid.
Calculate the number of moles of HCl in the solution and use your answer to
find the original mass of TiCl4
Moles of HCl...............................................................................................................
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Mass of TiCl4..............................................................................................................
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(4)
(b)
Calculate the volume of 1.10 mol dm-3 sodium hydroxide solution which would
be required to neutralise a 100 cm3 portion of the 1.20 mol dm-3 solution of
hydrochloric acid.
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(3) (Total 7 marks)
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