11 mark
A molecule contains carbon, hydrogen and oxygen. For every carbon atom there are twice as many hydrogen atoms but the same number of oxygen atoms.
What is the formula of the molecule?
C2H6O
C2H4O2
C4H8O2
C2H2O2
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Formulae (Cambridge O Level Chemistry)
Exam Questions
3 hours40 questions21 mark
Theobromine is a stimulant found in chocolate and in tea leaves and is closely related to caffeine, the stimulant found in coffee.
What is the formula of theobromine?
C6H5N4O2
C7H8N4O2
C7H8N3O2
C7H7N4O2
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31 mark
Hydrogen reacts with elements from Group VII to produce compounds called hydrogen halides. An example is when a molecule of hydrogen reacts with a molecule of fluorine to produce hydrogen fluoride.
What is the correct equation for the reaction?
2 H + 2 F → 2 HF
H2 + F2 → H2F2
2 H + 2 F → H2F2
H2 + F2 → 2 HF
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41 mark
Separate: Chemistry and Extended Only
Substance X was analysed and found to contain 40.00% carbon, 6.67% hydrogen and 53.33% oxygen by mass.
What is the empirical formula of X?
C4H8O4
C6H12O8
C2H4O2
CH2O
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11 mark
What is the balanced equation for the reaction of methane and oxygen?
CH4(g) + 2 O2(g) → CO2(g) + H2O(g)
CH4(g) + O2(g) → CO2(g) + 2 H2O(g)
2 CH4(g) + 4 O2(g) → 2 CO2(g) + H2O(g)
CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g)
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21 mark
A compound contains two atoms of oxygen and one atom of calcium. It also contains hydrogen in sufficient amounts so that the overall charge of the molecule is neutral.
What is the molecular formula for the compound?
Ca(OH)4
Ca(OH)2
H4CaO2
CaO2H2
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31 mark
Dilute sulfuric acid and barium chloride solution react to produce barium sulfate and hydrochloric acid, as shown in the reaction below:
H2SO4 + BaCl2 → BaSO4 + 2 HCl
Which row represents the correct state symbols for the reaction?
| H2SO4 | BaCl2 | BaSO4 | HCl | |
| A | (aq) | (l) | (s) | (aq) |
| B | (l) | (aq) | (aq) | (l) |
| C | (aq) | (aq) | (s) | (aq) |
| D | (l) | (aq) | (aq) | (l) |
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41 mark
The formula and charge for positive and negative ions are shown.
| cation | anion |
| Al3+, Mg2+, Cu2+, Fe2+, Li+ | F-, CO32-, NO3-, S2-, SO42- |
The table shows the name and formula of common ionic compounds formed from the ions. Which row is not correct?
| name | formula | |
| A | lithium sulfide | Li2S |
| B | iron(II) fluoride | Fe2F3 |
| C | aluminium sulfate | Al2(SO4)3 |
| D | magnesium nitrate | Mg(NO3)2 |
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51 mark
A substance was analysed and found to contain 26.57 % potassium, 35.36 % chromium, and 38.07 % oxygen by mass.
What is the empirical formula of the substance?
KCr2O7
K2CrO7
K2Cr2O5
K2Cr2O7
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61 mark
Substance X was analysed and found to contain 40.00 % carbon, 6.67 % hydrogen and 53.33 % oxygen by mass. The compound has a relative molecular mass of 60.0 g mol-1.
What is the molecular formula of X?
C4H8O4
C6H12O8
C2H4O2
CH2O
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71 mark
The empirical formula of compound X is CH2 and the relative molecular mass, Mr, of X is 70.
What is the molecular formula of X?
CH2
C2H4
C5H10
CnH2n
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81 mark
How many elements combine to form the compound ammonium sulfate?
2
4
10
15
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91 mark
The equation for the reaction between ethyne, C2H2, and oxygen is shown.
2C2H2(g) + xO2(g) → yCO2(g) + zH2O(g)
When the equation is balanced, what is x?
2
3
4
5
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11 mark
The left hand side for the reaction between ammonia and copper(II) oxide is shown. What are the products of the balanced equation?
3 CuO + 2 NH3 →
3 Cu + 2 N + 3 H2O
3 Cu + 3 HNO3
3 Cu + N2 + H2O
3 Cu + N2 + 3 H2O
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21 mark
What is the balanced equation for the reaction between aqueous NaOH and Fe2(SO4)3?
Fe2(SO4)3 (aq) + 6 NaOH (aq) → 2 Fe(OH)3 (s) + 3 Na2SO4 (aq)
Fe2(SO4)3 (aq) + 2 NaOH (aq) → Fe(OH)3 (s) + Na2SO4 (aq)
2 Fe2(SO4)3 (aq) + 4 NaOH (aq) → Fe(OH)3 (s) + Na2SO4 (aq)
3 Fe2(SO4)3 (aq) + 6 NaOH (aq) → 3 Fe(OH)3 (s) + 2 Na2SO4 (aq)
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31 mark
Magnesium nitrate and sodium carbonate react as shown.
Mg(NO3)2(aq) + Na2CO3(aq) → MgCO3(s) + 2 NaNO3(aq)
Which row describes the spectator ions and the net ionic equation for the reaction?
| spectator ions | net ionic equation | |
| A | Mg2+ and CO32- | Mg2+(aq) + CO32-(aq) → MgCO3(s) |
| B | NO3- and Na+ | NO3-(aq) + Na+(aq) → NaNO3(aq) |
| C | Mg2+ and CO32- | NO3-(aq) + Na+(aq) → NaNO3(aq) |
| D | NO3- and Na+ | Mg2+(aq) + CO32-(aq) → MgCO3(s) |
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41 mark
Nitric acid and potassium hydroxide react in a neutralisation reaction to produce salt and water, as shown by the equation below:
HNO3(aq) + KOH(aq) → KNO3(aq) + H2O(l)
Which row describes the spectator ions and the net ionic equation for the reaction?
| spectator ions | net ionic equation | |
| A | NO3- and K+ | NO3-(aq) + K+(aq) → KNO3(aq) |
| B | H+ and OH- | NO3-(aq) + K+(aq) → KNO3(aq) |
| C | NO3- and K+ | H+(aq) + OH-(aq) → H2O(l) |
| D | H+ and OH- | H+(aq) + OH-(aq) → H2O(l) |
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