OCR Gateway GCSE Chemistry

Topic Questions

GCSEChemistryOCR GatewayTopic Questions5. Monitoring & Controlling Chemical Reactions5.1 Monitoring Chemical Reactions

5.1 Monitoring Chemical Reactions

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1
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Zinc nitrate thermally decomposes to give two gases.

2Zn(NO3)2 (s) → 2ZnO (s) + 4NO2 (g) + O2 (g)

A student heats 1.89 g of zinc nitrate until there is no further reaction.

What is the total volume of gas measured at room temperature and pressure, made in this reaction?

• Assume that one mole of gas occupies a volume of 24 dm3 at room temperature and pressure.

• The molar mass of zinc nitrate is 189 g/mol.

  • 0.12 dm3

  • 0.48 dm3

  • 0.60 dm3

  • 1.20 dm3

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2
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How much 0.2 mol / dm3 hydrochloric acid solution could you make from 100 cm3 of 1.0 mol / dm3 hydrochloric acid?

  • 20 cm3

  • 200 cm3

  • 500 cm3

  • 600 cm3

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31 mark

Higher Only

Which procedure is the most suitable for preparing a 0.10 mol / dm3 solution of sodium carbonate?

  • The relative formula mass, Mr, of sodium carbonate is 106.

  • Dissolving 10.6 g of sodium carbonate in water to make 1.0 dm3 of solution.

  • Dissolving 10.6 g of sodium carbonate in 0.10 dm3 of water.

  • Dissolving 10.6 g of sodium carbonate in 1.0 dm3 of water.

  • Dissolving 106 g of sodium carbonate in water to make 1.0 dm3 of solution.

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1
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A solution of CuSO4 has a concentration of 35 g/dm3.

What mass of CuSO4 would there be in 250 cm3 of the solution?

  • 140 g

  • 8.75 g

  • 7.14 g

  • 1.40 g

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2
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A student carrying out a titration finds that a 25.0 cm3 solution of 0.500 mol/dm3 hydrochloric acid neutralises 35.0 cm3 of sodium hydroxide. 

The balanced symbol equation for the reaction is:

NaOH + HCl  →    NaCl  + H2O

What is the concentration of the sodium hydroxide?

  • 0.15 mol/dm3

  • 0.36 mol/dm3

  • 0.72 mol/dm3

  • 1.00 mol/dm3

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3
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How much solute is present in 2 dm3 of a 0.5 mol/dm3 solution of potassium iodide?

  • 0.5 mol

  • 1.0 mol

  • 2.0 mol

  • 10 mol

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4
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In a titration 25.00 cm3 of 0.20 mol/dm3 sodium hydroxide reacted with 26.50 cm3 of hydrochloric acid.

HCl + NaOH  → NaCl + H2O

What is the concentration of the acid?

  • 0.19 mol/dm3

  • 0.23 mol/dm3

  • 0.55 mol/dm3

  • 0.82 mol/dm3

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5
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A student titrated 25.00 cm3 of 0.40 mol/dm3 potassium hydroxide solution against sulfuric acid and found that 23.55 cm3 of the acid was required to reach the end point.

H2SO4 + 2KOH  →  K2SO4 + 2H2O

What is the concentration of the sulfuric acid?

  • 0.42 mol/dm3

  • 0.105 mol/dm3

  • 0.35 mol/dm3

  • 0.21 mol/dm3

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6
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What is the volume occupied by 5.6 g of nitrogen gas at RTP?

Relative atomic masses (Ar): N = 14

  • 2.4 dm3

  • 4.8 dm3

  • 9.6 dm3

  • 12 dm3

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7
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The reaction between nitrogen and hydrogen produces ammonia.

N2 (g) + 3H2 (g) begin mathsize 14px style rightwards harpoon over leftwards harpoon end style  2NH3 (g)

What volume of ammonia is produced from 565 cm3 of hydrogen?

  • 1130 cm3

  • 377 cm3

  • 283 cm3

  • 847 cm3

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8
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Air bags contain sodium azide (NaN3) which decomposes on heating to form sodium and nitrogen.

2NaN3       →       2Na       +       3N2

What volume of nitrogen would be produced from 13 g of sodium azide?

Relative atomic mass (Ar): N = 14

Relative formula mass (Mr): NaN3 = 65

  • 4.8 dm3

  • 7.2 dm3

  • 48 dm3

  • 72 dm3

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9
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A gas cylinder has a volume of 264 dm3.   

What mass of hydrogen does it contain?

Relative atomic masses (Ar): H = 1

  • 22 g

  • 11 g

  • 24 g

  • 264 g

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10
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A student made zinc chloride by reacting 15.0 g of zinc carbonate with hydrochloric acid.

ZnCO3 + 2HCl →  ZnCl2 + CO2 + H2O

The percentage yield of zinc chloride was 82.4%.

Calculate the mass of zinc chloride the student actually produced.

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

  • 13.4 g

  • 15.0 g

  • 16.3 g

  • 12.4 g

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11
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A student made magnesium oxide by reacting 2.4 g of magnesium with steam:

Mg (s) + H2O (g)  → MgO (s) + H2 (g)

She calculated the theoretical yield should be 4.0 g of magnesium oxide, but she only obtained 3.2 g.

What was the percentage yield for the experiment?

  • 60%

  • 70%

  • 75%

  • 80%

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12
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An equation for the reaction between copper(II) oxide and carbon is:

2CuO + C  → 2Cu + CO2

What is the percentage atom economy for the reaction to produce copper metal?

Relative atomic masses (Ar):     C = 12        Cu = 64

Relative formula mass (Mr):       CuO = 80

  • 64%

  • 59.3%

  • 74.4%

  • 92%

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131 mark

Which of these is/are a factor(s) in choosing a reaction pathway?

  Atom economy Percentage yield Rate of reaction
A ✔    
B ✔ ✔  
C   ✔ ✔
D ✔ ✔ ✔

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141 mark

Which statement describes the atom economy of a reaction?

  • A measure of how many atoms in the reactants form the waste products.

  • A measure of how many atoms in the reactants form the desired product.

  • A measure of the actual yield of product compared to the predicted yield of product.

  • A measure of how many atoms form waste products compared to desired products.

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151 mark

Hydrogen gas, H2, reacts with oxygen gas, O2, to make water, H2O.

2H2 + O2 → 2H2O

What is the atom economy for this reaction?

Mr : H2 = 2, O2 = 32, H2O = 18.

  • 50%

  • 53%

  • 89%

  • 100%

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161 mark

Which statement about atom economy is correct?

  • A reaction that has only one product has a higher atom economy than a reaction that has two products, one of them being a waste product.

  • A reaction with a low atom economy is more sustainable than a reaction with a high atom economy.

  • A reaction with a low atom economy will usually produce less waste products than a reaction with a high atom economy.

  • To calculate the atom economy of a reaction you need to know the expected yield and the actual yield of the products.

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17
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A student is making a fertiliser called potassium nitrate, KNO3.

Look at the equation for the reaction she uses.

KOH + HNO3 ➞ KNO3 + H2O

The relative formula masses, Mr, of each compound are shown in the table.

Compound Formula Relative formula mass
potassium hydroxide KOH 56.1
nitric acid HNO3 63.0
potassium nitrate KNO3 101.1
water H2O 18.0

What is the atom economy for the reaction to make potassium nitrate?

Assume that water is a waste product.

  • 15.1%

  • 47.1%

  • 52.9%

  • 84.9%

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18
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In the Haber process, nitrogen reacts with hydrogen to make ammonia.

N2 (g) + 3H2 (g) ⇌ 2NH3 (g)

What is the maximum volume of ammonia, NH3, that can be made from 150 cm3 of hydrogen, H2?

  • 50 cm3

  • 100 cm3

  • 225 cm3

  • 450 cm3

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191 mark

Higher Only

Which is the correct expression for calculating the concentration of a solution in g / dm3?

  • Concentration = fraction numerator volume space of space solution space in space dm cubed over denominator mass space of space solute space in space straight g end fraction

  • Concentration = fraction numerator amount space of space solute space in space mol over denominator mass space of space solute space in space straight g end fraction

  • Concentration = fraction numerator mass space of space solute space in space straight g over denominator volume space of space solution space in space cm cubed space cross times space 1000 end fraction

  • Concentration = fraction numerator mass space of space solute space in space straight g over denominator volume space of space solution space in space dm cubed end fraction

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201 mark

Higher Only

Chemists often have a choice of reaction pathway when making a new product.

Which factor do chemists consider when choosing a reaction pathway?

  • Disposal of product

  • Price they can charge for the product

  • Rate of reaction

  • Usefulness of waste reactants

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211 mark

Higher Only

Which of the following is the expression used to calculate concentration in g/dm3?

  • Concentration space equals space fraction numerator mass space of space solute space in space straight g over denominator volume space of space solution space in space dm cubed end fraction

  • Concentration space equals space fraction numerator mass space of space solvent space in space straight g over denominator volume space of space solution space in space dm cubed end fraction

  • Concentration space equals space mass space of space solute space in space straight g space cross times space volume space of space solution space in space dm cubed

  • Concentration space equals space fraction numerator mass space of space solute space in space straight g space cross times space volume space of space solution space in space dm cubed over denominator 1000 end fraction

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