Author: nashton
Company: RM plc

F321 module 1 Practice 3:
1.	Barium metal can be extracted from barium oxide, BaO, by reduction with aluminium.
	6BaO + 2Al → 3Ba + Ba_3Al_2O_6
Calculate the mass of barium metal that could be produced from reduction of 500 g of barium oxide using this method.
answer = ............................... g
[Total 4 marks]

2.	Magnesium exists naturally as a mixture of its isotopes, ^24Mg, ^25Mg and ^26Mg.
The isotopes in magnesium can be separated by mass spectrometry. The diagram below shows a mass spectrometer.
(i)	Complete the table below to show the composition of the ^25Mg and ^26Mg isotopes.
protons | neutrons | electrons
^25Mg | | |
^26Mg | | |
[2]
 
(ii)	Complete the electronic configuration of an atom of ^24Mg.
1s^2 ....................................................................................................................
[1]

(iii)	Results from the mass spectrum of a sample of magnesium are shown below.
isotope | ^24Mg | ^25Mg | ^26Mg
relative isotopic mass | 24.00 | 25.00 | 26.00
% abundance | 78.60 | 10.11 | 11.29
Calculate the relative atomic mass of the sample of magnesium.
Give your answer to two decimal places.
answer ...............................
[2]
[Total 5 marks]

3.	Magnesium reacts with oxygen to form magnesium oxide.
2Mg(s) + O_2(g) → 2MgO(s)
(i)	Use oxidation numbers to show that oxygen has been reduced in its reaction with magnesium.
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[2]
(ii)	Draw a ‘dot-and-cross’ diagram to show the arrangement of electrons in magnesium oxide. Show outer electron shells only and include any charges.
[2]
[Total 4 marks]

4.	Old samples of magnesium oxide become contaminated with magnesium carbonate.
(i)	Suggest how this contamination takes place.
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[1]
 
(ii)	A student added an excess of hydrochloric acid to an old sample of magnesium oxide that is contaminated with magnesium carbonate.
State two observations that the student would make.
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[2]
 
(iii)	Explain, with the aid of equations, why the resulting solution contained only one dissolved compound of magnesium.
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[3]
[Total 6 marks]

5.	Water, ammonia and sulphur dioxide react together to form a compound A which has the following percentage composition by mass:
N, 24.12%;
H, 6.94%;
S, 27.61%;
O, 41.33%.
(i)	Calculate the empirical formula of compound A.
[2]

(ii)	Suggest a balanced equation for the formation of compound A from the reaction of water, ammonia and sulphur dioxide.
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[1]
[Total 3 marks]

6.	A student carried out two experiments using chlorine gas, Cl_2(g).
(a)	In the first experiment, the student bubbled chlorine through 120 cm^3 of an aqueous solution of 0.275 mol dm^–3 sodium hydroxide, NaOH(aq).
The equation for this reaction is shown below.
Cl_2(g) + 2NaOH(aq) → NaCl(aq) + NaClO(aq) + H_2O(l)
Under the reaction conditions, 1 mole of Cl_2(g) occupies 24.0 dm^3.
 
(i)	What is meant by the term the mole?
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[1]
 
(ii)	How many moles of NaOH were in the 120 cm^3 volume of NaOH(aq)?
answer ....................... mol
[1]
(iii)	Calculate the volume of Cl_2(g) that was needed to react with the NaOH(aq) used.
answer ...............................
[2]
(iv)	What is a common use for the solution that the student prepared?
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[1]
 
(b)	In the second experiment, the student repeated the procedure in (a) but with hot concentrated sodium hydroxide. A different reaction took place in which sodium chlorate (V) was formed instead of NaClO.
Suggest the formula of sodium chlorate (V).
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[1]
[Total 6 marks]

7.	Both calcium carbonate, CaCO_3, and calcium oxide, CaO, are white solids.
Dilute hydrochloric acid, HCl, can be used to identify whether a sample of white solid is CaCO_3 or CaO.
(i)	Write equations, including state symbols, for the reaction of HCl with CaCO_3 and the reaction of HCl with CaO.
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[3]
 
(ii)	How would observation of the reactions with hydrochloric acid allow the identification of the white solid?
CaCO_3 .............................................................................................................
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CaO ................................................................................................................
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[1]
[Total 4 marks]

8.	Antimony, Sb, is a metal used in alloys to make lead harder. Bullets contain about 1% of antimony for this reason.
Antimony has two main isotopes.
(i)	What do you understand by the term isotopes?
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[1]
 
(ii)	Complete the table below to show the properties of particles that make up isotopes.
proton | neutron | electron
relative mass | | |
relative charge | | |
[2]
[Total 3 marks]

9.	Relative atomic mass, A_r, can be used to compare the masses of atoms of different elements.
(i)	Explain what you understand by the term relative atomic mass.
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[3]

(ii)	The antimony in a bullet was analysed by a forensic scientist to help solve a crime. The antimony was found to have the following percentage composition by mass: ^121Sb, 57.21%; ^123Sb, 42.79%.
	Calculate a value for the relative atomic mass of the antimony. Give your answer to 4 significant figures.
A_r ...................................
[2]
[Total 5 marks]

10.	Antimony is found naturally in a number of minerals including stibnite. Stibnite typically contains 5% of Sb_2S_3. Antimony can be obtained by reducing Sb_2S_3 with scrap iron.
		Sb_2S_3 + 3Fe → 2Sb + 3FeS
(i)	How many moles of Sb_2S_3 are in 500 kg of a typical sample of stibnite containing 5% by mass of Sb_2S_3?
molar mass of Sb_2S_3 = 340 g mol^–1; relative atomic mass of Sb = 122
……………… mol
[2]
 
(ii)	Calculate the mass of antimony that could be obtained by processing 500 kg of stibnite.
mass = ……………… kg
[2]
[Total 4 marks]

The King's CE School