Calculations Involving Masses (Edexcel GCSE Chemistry)

Exam Questions

3 hours32 questions
1a1 mark

This question is about relative formula mass.

What is the relative atomic mass of a sodium atom?
You will need to use a Periodic Table.

A 11
B 12
C 23
D 46
1b3 marks

Draw one straight line from each formula to its relative formula mass.

(relative atomic masses: H = 1, C = 12, O = 16)

edx-1-6-easy-paper-1-q1b

1c1 mark

Put these molecules in order of relative formula mass, lowest first.

Ammonia (NH3), nitrogen monoxide (NO), water (H2O)

(relative atomic masses: H = 1, N = 14, O = 16)

1d1 mark

Calculate the relative formula mass of a nitrogen molecule.

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2a1 mark

In an experiment, 3.5 g of lithium reacted with 4.0 g of oxygen to form a compound.

Complete the word equation for this reaction to show the name of the compound.

Lithium + oxygen → …………………….

2b3 marks

Calculate the empirical formula of this compound. 
(relative atomic masses: Lithium = 7, Oxygen = 16)

You must show your working.

2c1 mark

Complete this sentence to describe the law of conservation of mass:

The total mass of the reactants in a chemical reaction is equal to the total mass of the ……..

2d1 mark

All of the lithium reacts.

Calculate the mass of the compound formed.

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3a1 mark

A student burns some carbon in air.

The word equation for the reaction is:

Carbon + oxygen → carbon dioxide

Why does the mass of carbon decrease as it is burnt?

A The carbon atoms are disappearing
B The carbon atoms are forming a gas
C The carbon atoms are burning
D The carbon atoms are getting smaller
3b2 marks

The symbol equation for the reaction is:

C + O2 → CO2

State if this equation is balanced.

Explain your answer.

3c1 mark

 How many atoms are in one molecule of carbon dioxide?

3d2 marks

Calculate the mass of carbon dioxide that can be made by completely burning 6 g of carbon in oxygen.

(relative atomic mass of C: 12, relative formula mass of CO2: 44)

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4a1 mark

In an experiment 24.5 g of lead nitrate solution (Pb(NO3)2) is mixed with 25.3 g of potassium iodide solution (KI).

The products of the reaction are potassium nitrate solution (KNO3) and lead iodide (PbI2).

The equation for the reaction is:

Pb(NO3)(aq)  +  KI (aq)   → KNO(aq)  +    PbI(s)

Which substance in the reaction is a precipitate?

4b2 marks

The potassium iodide solution was made by adding 50 g of potassium iodide to 0.5 dm3 of water.

Calculate the concentration of the solution in g dm-3.
Use the formula: concentration (g dm-3) = mass (g) / volume (dm-3)
Show your working out.

4c1 mark

State how many atoms are present in Pb(NO3)2

4d1 mark

Calculate the total mass of the products.

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5a2 marks

Figure 2 shows information about different molecules.

Molecule

Structural formula

Relative formula mass

Molecular formula

Empirical formula

Water

 edx-1-6-easy-paper-1-q5a1

18

H2O

H2O

Hydrogen peroxide

 edx-1-6-easy-paper-1-q5a2

 

H2O2

 

Ethane

edx-1-6-easy-paper-1-q5a3

30

 

 

Figure 2

Calculate the relative formula mass of hydrogen peroxide.

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

5b1 mark

Explain why water has the same empirical and molecular formula.

5c1 mark

State the empirical formula of hydrogen peroxide.

5d2 marks

State the:

i)
Molecular formula of ethane

[1]

ii)
Empirical formula of ethane

[1]

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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)

2b1 mark

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

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

2c
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2 marks

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 = .....................................................

2d
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3 marks

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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1 mark

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

5b2 marks

Calculate the relative formula mass of butene, C4H8.

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

relative formula mass ................................
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)
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
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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1 mark

Higher Only

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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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)

1b
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5 marks
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

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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1 mark

Higher Only

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

3b
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2 marks

Higher Only

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)

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+ + ...................
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.

3e
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3 marks

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.

4b1 mark

Complete the balanced symbol equation for the reaction.

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

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)

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.

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)

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.

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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