3 Amount o substance
OCR Chemistry A Exam-style questions
1 A popular children s breakfast cereal is 35% sugar. A recommended portion si e
is 30 g. This sugar is called sucrose and has a chemical formula of C12H22O11.
a What mass of sugar is found in one portion of cereal?
(1 mark)
b Determine the relative molecular mass of sucrose.
(1 mark)
c How many moles of sugar are found in one portion of cereal?
(1 mark)
d Calculate the number of sucrose molecules in one portion of cereal.
Give your answer to three significant figures.
Number of sucrose molecules (1 mark)
2 9.72 g of magnesium reacts completely with oxygen to produce magnesium
oxide according to the following reaction:
2Mg O2 2MgO Reaction 2.1
a i Calculate the number of moles of magnesium used.
Number of moles of magnesium (1 mark)
ii Calculate the maximum mass of magnesium oxide that could be
produced in this reaction.
Maximum mass of magnesium oxide (2 marks)
, 3 Amount o substance
OCR Chemistry A Exam-style questions
iii The actual mass of magnesium oxide produced was 11.90 g. Calculate
the percentage yield. Give your answer to three significant figures.
Percentage yield % (1 mark)
b Magnesium oxide is also made by the following reaction:
Mg CuO MgO Cu Reaction 2.2
i Determine the atom economy for the production of magnesium oxide
using Reaction 2.2.
Atom economy % (1 mark)
ii Which method of making magnesium oxide will have the higher atom
economy out of Reaction 2.1 and Reaction 2.2? Explain your answer.
(1 mark)
3 When magnesium reacts with acid the reaction is exothermic it gives out heat.
Magnesium reacts with hydrochloric acid according to the following reaction:
Mg 2HCl MgCl2 H2 Reaction 3.1
The following apparatus was set up to measure the volume of gas evolved:
a 0.73 g of magnesium was added to excess hydrochloric acid.
i What is the purpose of having the magnesium inside the test tube within
the conical flask?
(1 mark)
OCR Chemistry A Exam-style questions
1 A popular children s breakfast cereal is 35% sugar. A recommended portion si e
is 30 g. This sugar is called sucrose and has a chemical formula of C12H22O11.
a What mass of sugar is found in one portion of cereal?
(1 mark)
b Determine the relative molecular mass of sucrose.
(1 mark)
c How many moles of sugar are found in one portion of cereal?
(1 mark)
d Calculate the number of sucrose molecules in one portion of cereal.
Give your answer to three significant figures.
Number of sucrose molecules (1 mark)
2 9.72 g of magnesium reacts completely with oxygen to produce magnesium
oxide according to the following reaction:
2Mg O2 2MgO Reaction 2.1
a i Calculate the number of moles of magnesium used.
Number of moles of magnesium (1 mark)
ii Calculate the maximum mass of magnesium oxide that could be
produced in this reaction.
Maximum mass of magnesium oxide (2 marks)
, 3 Amount o substance
OCR Chemistry A Exam-style questions
iii The actual mass of magnesium oxide produced was 11.90 g. Calculate
the percentage yield. Give your answer to three significant figures.
Percentage yield % (1 mark)
b Magnesium oxide is also made by the following reaction:
Mg CuO MgO Cu Reaction 2.2
i Determine the atom economy for the production of magnesium oxide
using Reaction 2.2.
Atom economy % (1 mark)
ii Which method of making magnesium oxide will have the higher atom
economy out of Reaction 2.1 and Reaction 2.2? Explain your answer.
(1 mark)
3 When magnesium reacts with acid the reaction is exothermic it gives out heat.
Magnesium reacts with hydrochloric acid according to the following reaction:
Mg 2HCl MgCl2 H2 Reaction 3.1
The following apparatus was set up to measure the volume of gas evolved:
a 0.73 g of magnesium was added to excess hydrochloric acid.
i What is the purpose of having the magnesium inside the test tube within
the conical flask?
(1 mark)
