A Level Official Exam Material
FREE Past Paper Questions by Topic
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Unit 1: Structure, Bonding and Introduction to Organic Chemistry
Topic 1: Formulae, Equations and Amount of Substance
For both AS and A Level students
Q1. How many atoms are there in 36.0 g of water?
[Avogadro constant = 6.02 × 1023 mol−1 ] (1)
A 3.010 × 1023
B 1.204 × 1024
C 2.408 × 1024
D 3.612 × 1024
(Total for question = 1 mark)
Q2. Calcium reacts with dilute nitric acid to form calcium nitrate and hydrogen.
Which is the balanced equation for this reaction?
A Ca + 2HNO3 → Ca(NO3)2 + H2
B Ca + H2NO3 → CaNO3 + H2
C Ca + 2H2NO3 → Ca(NO3)2 + 2H2
D 2Ca + 2HNO3 → 2CaNO3 + H2
(Total for question = 1 mark)
Q3. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross . Ammonium iron(II) sulfate, (NH4)2Fe(SO4)2·6H2O, is a double salt that is used as a source of iron(II) ions.
(a) What is the relative formula mass of the double salt?
[Ar values: H = 1.0 N = 14.0 O = 16.0 S = 32.1 Fe = 55.8] (1)
A 277.9
B 284.0
C 392.0
D 447.8
(b) Ammonium sulfate is used in the preparation of the double salt.
What types of bond are present in ammonium sulfate? (1)
A ionic only
B covalent and ionic only
C dative covalent and ionic only
D ionic, covalent and dative covalent
(c) What is the total number of ions present in 0.1 mol of the double salt?
[Avogadro constant (L) = 6.02 × 1023 mol−1 ] (1)
A 1.80 × 1023
B 2.41 × 1023
C 3.01 × 1023
D 6.62 × 1023
(Total for question = 3 marks)
Q4. This question is about iron and some of its compounds.
(a) A sample of iron contains the following isotopes.
Calculate the relative atomic mass of this sample of iron.
Give your answer to three significant figures. (2)
(b) Magnesium reacts with aqueous iron(II) sulfate in a displacement reaction.
Write the ionic equation for this reaction. Include state symbols. (2)
(c) 25.00 g of a compound contains 6.98 g of iron and 6.03 g of sulfur.
The remaining mass is oxygen. Calculate the empirical formula of this compound.
[Ar values: O = 16.0 S = 32.1 Fe = 55.8] (3)
(d) When 6.95 g of FeSO4.xH2O is heated, 2.00 g of iron(III) oxide, 0.80 g of sulfur dioxide and 1.00 g of sulfur trioxide are produced.
The only other product is water. Deduce the overall equation for the reaction using these data. State symbols are not required.
You must show your working.
[Ar values: H = 1.0 O = 16.0 S = 32.1 Fe = 55.8] (5)
Q5. This question is about compounds containing chlorine.
(a) A precipitate of silver chloride is formed when silver nitrate solution reacts with sodium chloride solution.
A student wrote an ionic equation for the reaction. Ag2+(l) + 2Cl– (l) → AgCl2(s)
Explain why this equation is incorrect, even though it is balanced. (2)
(b) A sample of a compound is analysed and found to contain only 3.09 g carbon, 0.26 g hydrogen and 9.15 g chlorine.
The molar mass of the compound is 97.0 g mol–1 .
Calculate the molecular formula of this compound.
You must show your working. (3)
(Total for question = 5 marks)
(e) A sample of gaseous cyclopentane with a volume of 25 cm3 was mixed with 250 cm3 of oxygen (an excess) and the mixture was ignited.
Only gaseous products were formed. 2C5H10(g) + 15O2(g) → 10CO2(g) + 10H2O(g)
Calculate the volume of each gas remaining after the reaction.
All the gas volumes were measured at the same temperature and pressure. (3)
Airbags protect occupants by inflating when a car crashes.
Airbags rely on chemical reactions to produce large volumes of gases quickly.
In some airbags, solid sodium azide (NaN3) decomposes forming nitrogen gas and sodium as the only products.
(a) Write an equation for the decomposition of sodium azide.
State symbols are not required. (1)
Q6. This question is about the compound ammonium dichromate(VI), (NH4)2Cr2O7.
(a) (NH4)2Cr2O7 breaks down at around 180 °C, producing an oxide of chromium, nitrogen and water as the only products. (i) Write an equation for the reaction.
State symbols are not required. (2)
(ii) Give a name for this type of reaction. (1)
Q7. This question is about atomic structure and gases.
(iii) A sample of chlorine contains 75.53 % of chlorine-35 atoms.
Calculate the relative atomic mass of this sample of chlorine.
Give your answer to two decimal places. (2)
(iv) Calculate, using the ideal gas equation, the volume in cm3 occupied by 0.0200 mol of ClF3 gas at a temperature of 60 °C and a pressure of 1.28 × 105 Pa.
Give your answer to an appropriate number of significant figures. [ pV = nRT R = 8.31 J mol−1 K −1 ] (4)
Q8. This question is about nitrogen.
(ii) Calculate the number of nitrogen atoms in 5.60 g of nitrogen gas.
[Avogadro constant = 6.02 × 1023 mol–1 ] (2)
(iii) A sample of nitrogen gas occupied 108 cm3 at a temperature of 25 °C and a pressure of 1.36 × 105 Pa.
Using the ideal gas equation, calculate the number of moles of nitrogen gas in this sample.
[pV = nRT R = 8.31 J mol–1 K –1 ] (4)
Q9. Magnesium is a metal in Group 2 of the Periodic Table.
It reacts with chlorine to form the salt magnesium chloride, MgCl2.
(c) Magnesium chloride can also be made by reacting magnesium oxide with dilute hydrochloric acid.
MgO(s) + 2HCl(aq) → MgCl2(aq) + H2O(l)
(i) Write the ionic equation, including state symbols, for this reaction. (1)
(ii) Calculate the minimum volume of 2.00 mol dm−3 hydrochloric acid needed to completely react with 2.45 g of magnesium oxide. (3)
Minimum volume of hydrochloric acid = ........................................................... cm3
(d) A further method for making magnesium chloride is by reacting magnesium carbonate with dilute hydrochloric acid.
MgCO3(s) + 2HCl(aq) → MgCl2(aq) + H2O(l) + CO2(g)
Calculate the maximum mass of magnesium chloride that could be formed when 2.25 g of magnesium carbonate is added to excess dilute hydrochloric acid. (2)
Maximum mass magnesium chloride = ........................................................... g
(e) Explain why the reaction to make magnesium chloride from magnesium oxide has a higher atom economy than the reaction using magnesium carbonate.
No calculation is required. (2)
............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(Total for question = 8 marks)
Q10. Alkanes and alkenes are obtained from crude oil. (e)
(i) Butane is used as a fuel. The equation for the complete combustion of butane is shown.
2C4H10(g) + 13O2(g) → 8CO2(g) + 10H2O(l)
35.0 cm3 butane is completely burned in 300 cm3 oxygen.
Calculate the final total volume of gas in cm3 .
All volumes are measured at the same temperature and pressure. (3)
(Total for question = 3 marks)
Q11. This question is about phosphorus and some of its compounds.
(d) In an experiment, 8.00 cm3 of 0.250 mol dm−3 sodium hydroxide, NaOH, reacted completely with 10.0 cm3 of 0.100 mol dm−3 phosphoric acid, H3PO4 .
Use these data to deduce the balanced equation for this reaction. You must show your working. (3)
(e) Hydrated magnesium phosphate has the formula Mg3(PO4)2.yH2O .
A sample of this compound contains 78.5% by mass of anhydrous magnesium phosphate.
Deduce the value of y. You must show your working.
[Molar mass of anhydrous magnesium phosphate, Mg3(PO4)2 = 262.9 g mol−1 ] (2)
(Total for question = 5 marks
Q12. (a) The relative atomic masses of elements can be determined using a mass spectrometer.
(i) Define the term relative atomic mass. (3) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(ii) Describe fully how positive ions are formed from gaseous atoms in a mass spectrometer. (2) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
Q13. Phenol, C6H5OH, is converted into trichlorophenol (known as TCP), C6H2Cl3OH, according to the equation below. C6H5OH + 3Cl2 → C6H2Cl3OH + 3HCl If 50.0 g of phenol produces 97.6 g of TCP,
what is the percentage yield of the TCP? [
Molar masses: phenol = 94 g mol−1 ; TCP = 197.5 g mol−1 ]
A 47.6%
B 49.4%
C 51.2%
D 92.9%
(Total for question = 1 mark)
Q14. This question is about a preparation of hydrated zinc sulfate crystals.
An excess of powdered zinc is added to 20 cm3 of 1.00 mol dm–3 sulfuric acid. (a)
(i) State two observations you would make during this reaction. (2) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(ii) Write the ionic equation for this reaction. Include state symbols. (2)
(b) When the reaction is complete, a solution of zinc sulfate is formed.
Some unreacted zinc is left.
Describe how pure dry crystals of hydrated zinc sulfate may be obtained from this mixture. (4) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(c) (i) The formula of the hydrated zinc sulfate crystals is ZnSO4.7H2O.
Calculate the molar mass of ZnSO4.7H2O. (1)
(ii) Calculate the number of moles of sulfuric acid in 20.0 cm3 of a 1.0 mol dm–3 solution. (1)
(iii) 4.00 g of hydrated zinc sulfate crystals form.
Calculate the percentage yield of hydrated zinc sulfate.
Give your answer to two significant figures. (2)
(Total for question = 12 marks)
Q15. A hydrocarbon contains, by mass, 82.7% carbon and 17.3% hydrogen.
The molecular formula of the hydrocarbon is
A CH3
B C2H6
C C2H5
D C4H10
(Total for question = 1 mark)
Q16. 2000 g of a solution contains 0.015 g of solute.
In the solution, the concentration of the solute in parts per million (ppm) is
A 3.0
B 7.5
C 30
D 75
(Total for question = 1 marks)
If you need the markscheme, including the examiners' reports for each question, and more exam and teaching materials on this topic, contact me through the contact page