GCSEChemistry: Combined ScienceOCR GatewayExam Questions3. Chemical Reactions3.1 Introducing Chemical Reactions

 Introducing Chemical Reactions (OCR Gateway GCSE Chemistry: Combined Science)

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3.1 Introducing Chemical Reactions

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3.1 Introducing Chemical Reactions

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11 mark

A student reacts calcium carbonate with hydrochloric acid.

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

What physical state does (g) represent in the balanced symbol equation?

  • Aqueous

  • Gas

  • Liquid

  • Solid

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21 mark

Look at the balanced symbol equation.


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


What does the symbol (s) represent in the balanced symbol equation?

  • Solid

  • Solute

  • Solution

  • Substance

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31 mark

The symbol of an aluminium ion is Al3+.

The symbol of an oxide ion is O2−.

What is the formula of aluminium oxide?

  • AlO

  • Al2O

  • Al3O2

  • Al2O3

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41 mark

The accurate relative atomic mass of aluminium is 26.9815385.

What is this number to 5 significant figures?

  • 26.98153

  • 26.981

  • 26.98154

  • 26.982

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51 mark

Which results show that the pH of a solution is acidic?

  • pH = 3, Universal indicator colour = orange 

  • pH = 10, Universal indicator colour = blue

  • pH = 3, Universal indicator colour = blue

  • pH = 10, Universal indicator colour = orange 

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61 mark

Why can the mass of a reaction in an open conical flask decrease?

  • One of the products is a gas.

  • One of the products is a solid.

  • One of the reactants is a liquid.

  • One of the reactants is a solid.

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71 mark

63.5g of copper reacts to make 134.5g of copper chloride, CuCl2

Cu + Cl2 → CuCl2


How much copper chloride will be made from 0.635g of copper?

  • 0.001345 g

  • 0.1345 g

  • 1.345 g

  • 13.45 g

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81 mark

Calcium carbonate, CaCO3, thermally decomposes to make calcium oxide, CaO, and carbon dioxide.

CaCO3 → CaO + CO2

5.0 g of calcium carbonate makes 2.8 g of calcium oxide.

How much carbon dioxide is made?

  • 2.2 g

  • 2.8 g

  • 4.4 g

  • 7.8 g

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11 mark

The formula of an iron(III) ion is Fe3+ and the formula of the sulfate ion is SO42-.

What is the formula of iron(III) sulfate?

  • Fe2SO4

  • Fe3(SO4)2

  • Fe2(SO4)3

  • (Fe)2(SO4)3

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21 mark

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

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

  • 3.01 x 1022

  • 3.01 x 1023

  • 6.02 x 1022

  • 6.02 x 1024

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31 mark

Which equation shows the formation of a Group 5 non-metal ion?

X represents a Group 5 non-metal and e- represents an electron.

  • X + e- → X-

  • X + 3e- → X3-

  • X  → X3-+ 3e-

  • X + 5e- → X5-

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41 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_q4-ocr-gcse-chemistry-mcq

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    5
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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

    • 11.0 g

    • 13.8 g

    • 15.0 g

    • 22.0 g

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    61 mark

    Symbol equations always need to have the same number of atoms on both sides.

    Which equation is correctly balanced?

    • H2SO4   +   2NaOH    →   Na2SO4   +   H2O

    • Ca(OH)2   +   2HCl    →    CaCl2   +   H2O­

    • 4Na   +   O­2­    →   2Na­2­O

    • 2Cu   +   8HNO3     →      2Cu(NO3)2  + 2NO +  4H2

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    7
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    How many moles are present in 9 kg of glucose, C6H12O6?

    Relative formula mass (Mr):       C6H12O6 = 180

    • 0.02 mol

    • 0.05 mol

    • 20 mol

    • 50 mol

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    8
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    What is the mass of 0.25 moles of hydrated copper(II) sulfate, CuSO4.5H2O?

    Relative formula mass (Mr):  H2O = 18  CuSO4 = 160

    • 40.0 g

    • 44.5 g

    • 62.5g

    • 1000 g

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    9
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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 (Ar):     Al = 27        I = 127

    Relative formula mass (Mr):      AlI3 = 408

    What coefficients would balance the equation for the reaction?

    • 1 : 3 : 2

    • 2 : 1 : 2

    • 2 : 3 : 2

    • 3 : 2 : 3

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    10
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    Nitrogen and hydrogen react together to make ammonia.

    N2 + 3H2  → 2NH3

    If 2.0 g of hydrogen is added to 12.0 g of nitrogen which substance is the limiting reactant and how much of the excess reactant remains?

    Relative atomic masses (Ar): H = 1    N = 14

      Limiting Reactant Mass of excess reactant
    A nitrogen 2.0 g
    B nitrogen 10.0 g
    C hydrogen 2.7 g
    D hydrogen 9.3 g

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      11
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      When 12 g of carbon (C) burns in oxygen (O2), 44 g of carbon dioxide (CO2) is formed.

      What mass of C would burn to form 11 g of CO2?

      • 3 g

      • 4 g

      • 11 g

      • 12 g

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      121 mark

      Lead nitrate contains lead ions, Pb2+, and nitrate ions, NO3-.

      What is the formula for lead nitrate?

      • PbNO3

      • Pb(NO3)2

      • Pb2NO3

      • Pb2(NO3)2

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      13
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      Hydrogen gas can be made by reacting methane and steam (H2O).

      CH4 + H2O rightwards arrow3H2 + CO

      6 g of hydrogen gas can be made from 18 g of steam, H2O.

      How much hydrogen gas can be made from 3.6 g of steam, H2O?

      • 0.4 g

      • 0.6 g

      • 1.2 g

      • 6.8 g

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      141 mark

      Ethanol, C2H5OH, burns in oxygen. Carbon dioxide and water are made.

      Which equation for this reaction is correctly balanced?

      • C2H5OH + O2 → CO2 + H2O

      • C2H5OH + 3O2 → 2CO2 + 3H2O

      • C2H5OH + 2O2 → 3CO2 + 2H2O

      • 2C2H5OH + 7O2 → 4CO2 + 6H2O

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      151 mark

      Oxygen reacts with 1.20 g of carbon. 4.40 g of carbon dioxide forms.

      C + O2 → CO2

      What mass of oxygen is used in this reaction?

      • 0.80 g

      • 1.60 g

      • 3.20 g

      • 5.60 g

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      161 mark

      The formula of a magnesium ion is Mg2+.

      The formula of a nitrate ion is NO3-.

      What is the formula of magnesium nitrate?

      • MgNO3

      • Mg2NO3

      • Mg(NO3)2

      • Mg2(NO3)3

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      17
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      Higher Only

      Urea, (NH2)2CO, is a fertiliser.

      A student makes 1 mole of urea from 2 moles of ammonia.

      What is the mass of urea that the student makes?

      • 43.0 g

      • 44.0 g

      • 58.0 g

      • 60.0 g

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      181 mark

      Magnesium reacts with chlorine. Magnesium chloride is made.

      What is the balanced symbol equation for this reaction?

      • Mg + Cl → MgCl

      • Mg + Cl2 → MgCl2

      • 2Mg + Cl2 → 2MgCl

      • 2Mg + Cl2 → Mg2Cl2

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      191 mark

      Which of these shows the balanced symbol equation for the reaction between potassium and chlorine to make potassium chloride?

      • K + Cl2 ➞ KCl2

      • P + Cl2 ➞ PCl2

      • 2K + Cl2 ➞ 2KCl

      • 2P + Cl2 ➞ 2PCl

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      201 mark

      Magnesium is heated in a crucible.

      q11-paper-3-june-2018-ocr-gcse-chem

      The mass of the crucible and magnesium increases.

      Which statement is the best explanation for this?

      • Oxygen is given off.

      • The magnesium melts.

      • The magnesium is oxidised to magnesium oxide.

      • The magnesium reacts to make magnesium carbonate.

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      211 mark

      Higher Only

      A student neutralises nitric acid with potassium hydroxide solution.

      Which equation shows the ionic equation for neutralisation?

      • HNO3 + KOH → KNO3 + H2O

      • H+ + OH– → H2O

      • NO3 – + K+ → KNO3

      • H+ + NO3 – → HNO3

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      22
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      What is the amount, in mol, of 15 g of carbonate ions, CO32-?

      • 0.18

      • 0.25

      • 4.0

      • 5.6

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      231 mark

      Look at the diagram.

      q15-paper-3-specimen-2016-ocr-gcse-chem

      It shows how the reaction between hydrochloric acid and marble chips (calcium carbonate) can be monitored.

      The reading on the balance decreases during the reaction.

      Which statement is the best explanation?

      • Acid escapes from the flask.

      • Carbon dioxide gas is made which leaves the flask.

      • Hydrogen gas is made which leaves the flask.

      • The temperature in the laboratory changes.

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      24
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      How many moles are in 30g of nitrogen, N2?

      Relative atomic mass (Ar): N = 14.0

      • 0.47mol

      • 0.93mol

      • 1.07mol

      • 2.14mol

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      1
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      Avogadro’s constant has a value of 6.02 × 1023.

      How many oxygen atoms are in 0.25 moles of oxygen molecules?

      • 1.204 × 1024

      • 1.505 × 1023

      • 3.010 × 1023

      • 6.020 × 1023

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      2
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      Avogadro’s constant has a value of 6.02 × 1023.

      What is the number of atoms in 0.5 mol of water?

      • 2.00 × 1023

      • 3.01 × 1023

      • 6.02 × 1023

      • 9.03 × 1023

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      3
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      Methane burns in oxygen to form carbon dioxide and water.

      CH4 + 2O2 → CO2 + 2H2O

      Calculate the amount of carbon dioxide made when 6.4 g of methane is burnt.

      • 2.8 g

      • 4.4 g

      • 14.4 g

      • 17.6 g

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      4
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      Sodium hydroxide reacts with hydrochloric acid. Sodium chloride and water are made.

      NaOH + HCl → NaCl + H2O

      What mass of sodium hydroxide would be needed to make 46.8 g of sodium chloride?

      • 16 g

      • 32 g

      • 50 g

      • 64 g

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      51 mark

      Phosphoric acid contains phosphate ions, PO subscript 4 superscript 3 minus end superscript

      Phosphoric acid is completely neutralised by sodium hydroxide.

      What is the formula of the salt that is made?

      • Na2PO4

      • Na3PO4

      • Na(PO4)3

      • Na2(PO4)3

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      61 mark

      Calcium phosphate contains the ions Ca2+ and PO43–.

      What is the formula for calcium phosphate?

      • CaPO4

      • Ca2PO4

      • Ca2(PO4)3

      • Ca3(PO4)2

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