11 mark
Which equation is not a neutralisation reaction?
Ca (s) + 2HCl (aq) → CaCl2 (aq) + H2 (g)
H+ (aq) + OH– (aq) → H2O (l)
K2CO3 (s) + 2HNO3 (aq) → 2KNO3 (aq) + H2O (l) + CO2 (g)
NH3 (aq) + HCl (aq) → NH4Cl (aq)
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Acid-base & Redox Reactions (OCR AS Chemistry)
Exam Questions
3 hours44 questions2
1 mark
1 markWhat is the oxidation number of nitrogen in Mg(NO3)2?
-3
+2
+5
+6
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31 mark
Which equation represents a redox reaction?
Mg + 2HCl
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MgCl2 + H2MgO + 2HCl
H2O + MgCl2MgCO3+ 2HCl
CO2 + H2O + MgCl2Mg(OH)2 + 2HCl
MgCl2 +2H2O
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41 mark
Which reaction shows oxidation of sulfur?
2HBr + H2SO4 → SO2 + 2H2O + Br2
SO2 + 2NaOH → Na2SO3 + H2O
8HI + H2SO4 → 4I2 + H2S + 4H2O
H2S + Cl2 → 2HCl + S
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51 mark
What is the oxidation number of Mn in K2MnO4?
+4
+5
+6
+7
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61 mark
Which are the correct common oxidation states of fluorine, oxygen and hydrogen in compounds?
| Fluorine | Oxygen | Hydrogen | |
| A | -1 | -2 | +1 |
| B | -7 | -1 | -1 |
| C | +1 | +2 | +1 |
| D | +7 | -1 | -1 |
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71 mark
The heptahydrate mineral of magnesium sulfate is used in Epsom Salts for preparing therapeutic baths. Magnesium sulfate is also used in some medical applications.
What is the overall oxidation state of MgSO4?
-2
+2
+7
0
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81 mark
Europium metal reacts with sulfuric acid to form europium(III) sulfate and hydrogen gas.
What is the formula of europium(III) sulfate?
EuSO4
Eu(SO4)2
Eu2(SO4)3
Eu3(SO4)2
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91 mark
A reaction occurs between aqueous calcium hydroxide and nitric acid.
Which is the correct ionic equation for the reaction?
Ca(OH)2 + 2HNO3 → Ca(NO3)2 + H2O
H+ + OH- → H2O
Ca2+ + 2NO3- → Ca(NO3)2
CaOH + HNO3 → CaNO3 + H2O
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11 mark
Titanium dioxide can be obtained from the ore ilmenite, Fe(II)TiO3.
FeTiO3 → TiO2
What is the change in the oxidation number of titanium in the reaction?
+3 to +4
+4 to +5
+6 to +4
No change in oxidation number occurs
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21 mark
What is the oxidation number of Cr in Cr(H2O)63+?
0
+1
+2
+3
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31 mark
1 mark25.0 cm3 of hydrochloric acid solutions reacts with 36.2 cm3 of 0.225 mol dm-3 sodium hydroxide solution.
What is the concentration of the acid?
0.326 mol dm-3
8.15 x 10-3 mol dm-3
1.55 x 10-4 mol dm-3
0.65 mol dm-3
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41 mark
1 markWhen a sample of sodium hydroxide, NaOH, is dissolved in 250 cm3 of distilled water. 25.0 cm3 of this solution is titrated against sulfuric acid with a concentration of 2.00 mol dm-3. Complete neutralisation takes place with 15.0 cm3 of sulfuric acid.
2NaOH + H2SO4 → Na2SO4 + 2H2O
What is the mass of the original sample of sodium hydroxide dissolved in 250 cm3 of distilled water?
1.20 g
12.0 g
2.40 g
24.0 g
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51 mark
Which of the following represents a redox reaction?
Fe + 2HCl → FeCl2 + H2
2NH3 + HNO3 → NH4NO3
K2CO3 + 2CH3COOH → 2CH3COOK + CO2 + H2O
ZnO + H2SO4 → ZnSO4 + H2O
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61 mark
In which reaction does hydrogen behave as an oxidising agent?
H2 + CuO → Cu + H2O
2Na + H2 → 2NaH
H2 + Cl2 → 2HCl
C2H4 + H2 → C2H6
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71 mark
Which reaction shows the species in bold acting as an oxidising agent?
2MnO4- + 5SO32- + 6H+ → 2Mn2+ + 3H2O + 5SO42-
Fe2O3 + 3CO → 2Fe + 3CO2
Mg + Fe2+ → Mg2+ + Fe
Cl2 + 2Br- → 2Cl- + Br2
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81 mark
The following reaction can be used to determine the mass of titanium dioxide in an ore.
3TiO2 + 4BrF3 → 3TiF4 + 2Br2 + 3O2
Which element decreases in oxidation state in this reaction?
Oxygen
Fluorine
Bromine
Titanium
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91 mark
1 markA student titrate as a solution of strontium hydroxide, Sr(OH)2 (aq), with hydrochloric acid, HCl (aq). 25.00 cm3 of 0.055 mol dm-3 Sr(OH)2 was needed to neutralise 24.80 cm3 of HCl (aq).
What is the concentration of the acid?
0.03 mol dm-3
1.38 x 10-3 mol dm-3
0.11 mol dm-3
0.06 mol dm-3
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101 mark
What is the oxidation state of Cl in Cl2O7?
+14
+5
+7
0
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11 mark
1 markWhich reagent would exactly neutralise 100 cm3 of 1.00 mol dm–3 H2SO4 (aq)?
0.100 mol Al(OH)3
0.100 mol NH3
0.100 mol Ba(OH)2
0.100 mol NaOH
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21 mark
1 markIn the compound [ICl2]+ [SbCl6]- the oxidation number of chlorine is –1.
What are the oxidation numbers of I and Sb in the compound?
| I | Sb | |
| A | +1 | +5 |
| B | +1 | +7 |
| C | +3 | +5 |
| D | +3 | +7 |
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31 mark
A solution containing both bromine and chlorine will produce bromate ions, BrO3–.
The reactions leading to the production of BrO3– ions are:
Reaction 1: Br2 + H2O → HBr + HBrO
Reaction 2: 3HBrO + Cl2 → 2Cl – + BrO3– + Br2 + 3H+
Which statements about these reactions are correct?
| Chlorine is reduced in reaction 2 | Bromine is reduced in both reaction 1 and reaction 2 | Bromine is oxidised in both reaction 1 and reaction 2 | |
| A | ✓ | X | X |
| B | ✓ | ✓ | X |
| C | X | ✓ | ✓ |
| D | ✓ | ✓ | ✓ |
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41 mark
If a dilute acid is added to an aqueous solution containing nitrite ions, NO2–, two different nitrogen compounds are released as gases.
2H+ (aq) + 2NO2– (aq) → H2O (l) + NO (g) + NO2 (g)
Which of the three statements below correctly describe the process?
| The H+ (aq) ion is oxidised by NO2- (aq) | Some nitrogen atoms are oxidised, and some nitrogen atoms are reduced | The H+ (aq) ion acts as a catalyst | |
| A | ✓ | ✓ | X |
| B | X | ✓ | X |
| C | X | ✓ | ✓ |
| D | ✓ | ✓ | ✓ |
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51 mark
What are the correct oxidation numbers for the elements in Fe3O4?
| Fe | O | |
| A | +3 and +4 | -1 |
| B | +2.67 | -2 |
| C | +2 and +3 | -2 |
| D | +4 | -3 |
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61 mark
1 markA student performed a titration. The burette readings from one titration are shown below.
| Final reading / cm3 | 28.65 |
| Initial reading / cm3 | 7.25 |
The burette the student used has an uncertainty of ±0.05 cm3.
What is the percentage uncertainty of the resulting titre?
0.17%
0.23%
0.35%
0.47%
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71 mark
1 markA student titrated 25.0 cm3 of 0.30 mol dm-3 of aqueous potassium hydroxide, KOH (aq), with 0.10 mol dm-3 of aqueous phosphoric(V) acid, H3PO4 (aq). The equation for the reaction is shown below.
H3PO4 (aq) + 3KOH (aq) → K3PO4 (aq) + 3H2O (l)
Which statement is correct?
If the concentration of H3PO4 (aq) is doubled, the volume of KOH (aq) required to reach the end point will be halved.
The end point is reached when 25.0 cm3 of H3PO4 (aq) has been added.
Once the titration is complete, 0.00750 mol of H2O is present.
The end point is reached when 75.0 cm3 of H3PO4 (aq) has been added.
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81 mark
1 markA solution of an unknown carbonate, X2CO3, was prepared by dissolving 3.63 g in 250 cm3 of distilled water in a volumetric flask.
25.0 cm3 of the solution was titrated with 0.20 mol dm-3 hydrochloric acid. The mean titre of hydrochloric acid required to reach the end point was 26.20 cm3.
Which is the correct identity of X?
Sodium
Magnesium
Potassium
Calcium
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91 mark
1 mark30.0 cm3 of a 0.10 mol dm-3 solution of an unknown acid, HxA, reacted completely with 45 cm3 of a 0.200 mol dm-3 solution of lithium hydroxide.
Which is the correct equation for the reaction?
HA + LiOH → LiA + H2O
H2A + 2LiOH → Li2A + 2H2O
H3A + 3LiOH → Li3A + 3H2O
H2A + Li(OH)2 → LiA + 2H2O
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101 mark
1 markWhich one of the following is the electron arrangement of the element that is reduced most easily?
1s2 2s2 2p4
1s2 2s2 2p6 3s2 3p3
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5
1s2 2s2 2p6 3s2 3p6
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