Edexcel GCSE Chemistry: Combined Science

Topic Questions

GCSEChemistry: Combined ScienceEdexcelTopic Questions1. Atomic Structure1.6 Calculations Involving Masses

1.6 Calculations Involving Masses

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1a5 marks

Figure 13 shows a model of how particles are arranged in a solid.

fig-13-q8-1cho-1h-specimen-2018

Figure 13

 i)
State two ways in which this model fails to accurately represent a crystal of sodium chloride.

(2)

ii)
Magnesium oxide has a melting point of 2852 °C.
Explain why magnesium oxide has such a high melting point.

(3)

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1b
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i)
Carbon dioxide can be formed by the reaction of calcium carbonate, CaCO3 with dilute hydrochloric acid.

Write the balanced equation for this reaction.

(3)

ii)

The thermal decomposition of copper carbonate forms copper oxide and carbon dioxide.

CuCO3(s) → CuO(s) + CO2(g)

15.0 g of pure copper carbonate is decomposed completely.

Calculate the mass of solid produced.

(relative atomic masses: C = 12.0; O = 16.0; Cu = 63.5)

Give your answer to two significant figures.

(2)

mass of solid = ................................................................. g

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1c3 marks

Higher Only

Magnesium reacts with water in the form of steam as shown in the equation.

Mg + 2H2O → Mg(OH)2+ H2

2.4 g of magnesium reacts with sufficient steam for a complete reaction to form 5.8 g of magnesium hydroxide and 0.2 g of hydrogen.
Show, by calculation, that the law of conservation of mass applies to this reaction.
(relative atomic masses: H = 1.0, O = 16, Mg = 24)

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2
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2.7 g aluminium reacts with 38.1 g of iodine, I2, to make 40.8 g aluminium iodide, AlI3.

(Relative atomic masses:     Al = 27        I = 127

Relative formula mass:      AlI3 = 408)

What coefficients would balance the equation for the reaction?

  ☐ A 1 : 3 : 2
  ☐ B 2 : 1: 2
  ☐ C 2 : 3 : 2
  ☐ D 3 : 2 : 3

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3a4 marks

A student placed a piece of metal P in a test tube containing excess dilute sulfuric acid.
The student repeated this with three other metals, Q, R and S.
All the pieces of all four metals were the same size.

i)
The student recorded the observations until each metal had reacted with the acid for two minutes.
The observations are shown in Figure 9.

metal observations
P bubbles produced very slowly
some metal remained
Q bubbles produced quickly
no metal remained
R bubbles produced slowly
no metal remained
S bubbles produced very quickly
no metal remained

Figure 9

Use this information to put the four metals in order of reactivity from the least reactive to the most reactive.

(2)

least reactive         most reactive

ii)
Complete the diagram below to show how the student could add to the apparatus to measure the volume of gas produced in the two minutes.

(2)

fig-q9aii-1cho-1h-paper-1-june-2018

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3b
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When iron reacts with copper sulfate solution, solid copper is formed.
Two possible equations for this reaction are

A    CuSO4 + Fe → Cu + FeSO4
B    3CuSO4 + 2Fe →  3Cu + Fe2(SO4)3

It was found that 10.00 g of iron powder reacted with excess copper sulfate solution to produce 11.34 g of copper.
Carry out a calculation to decide which equation, A or B, represents the reaction taking place.

(relative atomic masses: Fe = 56.0, Cu = 63.5)

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3c2 marks

Higher Only

Acid solutions contain hydrogen ions.

Aluminium reacts with dilute hydrochloric acid to form a solution containing aluminium ions, Al3+.

Complete the balanced ionic equation for this reaction.


................... + .................. H+ rightwards arrow.................. AI3+ + ...................

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3d1 mark

Higher Only

The hydrogen ion concentration in a solution is decreased by a factor of 10.

State how the pH of this solution changes.

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3e
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Higher Only

Calculate the mass, in g, of a hydrogen atom, using the data below.
(relative atomic mass: H = 1.00;
Avogadro constant = 6.02 × 1023)

mass of hydrogen atom = ......................................g

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4a1 mark

Sodium hydroxide is added to sulfuric acid.

Name the type of reaction that takes place.

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4b1 mark

Complete the balanced symbol equation for the reaction.

2NaOH (aq) + H2SO4 (aq) → ………… (aq) + ………. (l)

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4c4 marks

Higher Tier Only

Calculate the mass of sodium hydroxide needed to add to 1 dm3 of water to make solution with a concentration of 0.2 mol dm-3.

Show your working out.

(relative atomic masses: Na = 23, O = 16, H = 1)

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4d4 marks

Higher Tier Only

Deduce which reactant is in excess when 100 cm3 of 0.2 mol dm-3 sodium hydroxide reacts completely with 50 cm3 of 0.5 mol dm-3 sulfuric acid.

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5a2 marks

A student reacted calcium carbonate with hydrochloric acid.
They wanted to investigate how the mass changed during the reaction.

Figure 1 shows the equipment they used.

edx-1-6h-paper-1-q5a-calcium-carbonate-and-acid-reaction

Figure 1

Give the function of the cotton wool.

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5b2 marks

The symbol equation for the reaction is:

CaCO3 (s) + 2HCl (aq) → CaCl2 (aq) + CO2 (g) + H2O (l)

Calculate the relative formula mass of calcium carbonate.

(relative atomic masses: Ca = 40, C = 12, O = 16)

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5c3 marks

Higher Tier Only

They used 0.25 mol of hydrochloric acid.

Calculate the minimum mass of calcium carbonate that must be added to react with all the hydrochloric acid.

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5d4 marks

The student measures the mass of the contents of the flask at the start and end of the reaction.

i)
Describe one way they could tell the reaction was over.

[1]

ii)
Explain why the results from this experiment do not appear to support the law of conservation of mass.

[3]

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11 mark

The diagram shows the displayed formula of succinic acid. 

2-1-displayed-formula-of-succinic-acidWhat is the empirical formula for this compound?

  ☐ A C4H6O4
  ☐ B CH2O
  ☐ C C2H3O2
  ☐ D CHO

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2a4 marks

The apparatus in Figure 7 shows a piece of magnesium ribbon being heated.

fig-7-q6-1cho-1f-specimen-2018

Figure 7

During the heating, the magnesium reacts with oxygen from the air. The lid of the crucible was raised slightly from time to time. Magnesium oxide was formed as a white powder. The experiment was repeated with different masses of magnesium.
The results are shown in Figure 8.

experiment mass of magnesium
used/g		 mass of magnesium
oxide formed/g		 mass of oxygen in
magnesium oxide/g
1 0.10 0.16 0.06
2 0.15 0.24 0.09
3 0.25 0.40 0.15
4 0.30 0.48 0.18
5 0.35 0.49 0.14
6 0.50 0.80 0.30

Figure 8

i)
Draw a graph of the mass of oxygen in magnesium oxide against the mass of magnesium used.
fig--q6ai-1cho-1f-specimen-2018
(3)
ii)
The result for experiment 5 is anomalous.
The masses were all measured accurately.

Suggest a reason for this anomalous result.

(1)

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2b1 mark

Balance the equation for the reaction of magnesium with oxygen to form magnesium oxide.

....................... Mg + ....................... O2→ ........................ MgO

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2c
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Calcium nitrate contains calcium ions and nitrate ions.

Calculate the relative formula mass of calcium nitrate, Ca(NO3)2.
(relative atomic masses: Ca = 40, N = 14, O = 16)

relative formula mass = .....................................................

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2d
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Two oxides of lead, R and S, were analysed.

The empirical formula of oxide R was found to be PbO.

The results of the analysis of oxide S showed it contained 0.207 g of lead combined with 0.032 g of oxygen.

Show, by calculation, that the two oxides had different empirical formulae.
(relative atomic masses: O = 16, Pb = 207)

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3
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A company produces tin from an ore called cassiterite, which is mainly tin oxide.

What is the relative formula mass (Mr) of tin oxide, SnO2?

Relative atomic masses (Ar):   Sn= 119 O= 16

  ☐ A 135
  ☐ B 151
  ☐ C 270
  ☐ D 1904

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41 mark

Higher Only

Avogadro's constant has a value of 6.02 x 1023.

How many hydrogen atoms are in 0.05 moles of hydrogen molecules?

  ☐ A 3.01 x 1022
  ☐ B 3.01 x 1023
  ☐ C 6.02 x 1022
  ☐ D 6.02 x 1024

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5a1 mark

The molecular formula of butene is C4H8.

Which of the following is the empirical formula of butene?

 
  ☐ A CH
  ☐ B CH2
  ☐ C C4H8
  ☐ D (CH2)4

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5b2 marks

Calculate the relative formula mass of butene, C4H8.

(relative atomic masses: H = 1, C = 12)

relative formula mass ................................

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5c1 mark

When burnt completely in air, butene forms carbon dioxide and water.

i)
Balance the equation for this reaction by putting numbers in the spaces provided.

C4H8 + 6O2 rightwards arrow ................ CO2 + ................ H2O
(2)
ii)
Describe the test to show that a gas is carbon dioxide.
(2)

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5d1 mark

Substance X is a gas at room temperature.
It is a simple molecular, covalent substance.

Which row of the table shows the properties that substance X is most likely to have?

  boiling point
in °C		 relative solubility
in water
square  A –6 low
square  B 600 high
square  C –6 high
square  D 600 low

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5e1 mark

Diamond has a giant covalent structure.

State one property of diamond that is the result of its giant covalent structure.

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61 mark

A piece of iron wool is left in moist air and goes rusty.

Which graph shows how the mass of the iron wool changes? 3-1-q-4-mass-changes

  ☐ A  
  ☐ B  
  ☐ C  
  ☐ D  

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7
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A student wanted to make 15.0 g of zinc chloride. The equation for the reaction is:

ZnCO3 + 2HCl →  ZnCl2 + CO2 + H2O

What mass of zinc carbonate should the student add to the hydrochloric acid to make 15.0 g of zinc chloride?

Relative atomic masses (Ar): C = 12    Zn = 65   O= 16    Cl = 35.5     H= 1

  ☐ A 11.0 g
  ☐ B 13.8 g
  ☐ C 15.0 g
  ☐ D 22.0 g

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