What is the oxidation number of chromium in Na2Cr2O7?
+1
+2
+3
+6
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What is the oxidation number of chromium in Na2Cr2O7?
+1
+2
+3
+6
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In an oxide of nitrogen, the oxidation number of nitrogen is +4.
Which is the formula of the oxide?
N2O
N2O3
N2O4
N2O5
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What is the oxidation number of phosphorus in the phosphate ion, P?
–3
+3
+5
+7
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Hydrogen peroxide, H2O2, breaks down into water and oxygen.
In terms of oxidation and reduction, how do hydrogen and oxygen change in this reaction?
Hydrogen | Oxygen | |||
☐ | A | oxidised | reduced | |
☐ | B | oxidised and reduced | unchanged | |
☐ | C | reduced | oxidised | |
☐ | D | unchanged | oxidised and reduced |
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Iodate(V) ions, I, oxidise dithionate ions, S2, according to the equation
x I+ y S2+ 4H2O → z S+ 8H++ I2
What are the balancing numbers x, y and z?
x | y | z | |||
☐ | A | 2 | 1 | 2 | |
☐ | B | 2 | 2 | 4 | |
☐ | C | 2 | 5 | 5 | |
☐ | D | 2 | 5 | 10 |
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Magnesium reacts with hydrochloric acid.
Mg (s) + 2HCl (aq) → MgCl2 (aq) + H2 (g)
Which statement about this reaction is correct?
magnesium atoms act as oxidising agents
hydrogen molecules act as reducing agents
hydrogen ions act as oxidising agents
chloride ions act as oxidising agents
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The formulae of four ions are shown.
Formula of ion |
CrO42- |
AlO2- |
[Fe(CN)6]4- |
[CrCl2(H2O)4]+ |
How many of these ions contain a metal with an oxidation number of +3?
one
two
three
four
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This question is about the reaction shown.
2KMnO4 + xH2C2O4 + yH2SO4 → 2MnSO4 + K2SO4 + 10CO2 + zH2O
x | y | z | |||
☐ | A | 5 | 6 | 8 | |
☐ | B | 10 | 3 | 4 | |
☐ | C | 5 | 3 | 8 | |
☐ | D | 10 | 6 | 4 |
H+
C2O42-
MnO4
SO4
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Which name is correct for the ion S ?
sulfate(II)
sulfate(IV)
sulfate(VI)
sulfate(VIII)
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A diprotic acid, H2A, was titrated with sodium hydroxide solution.
H2A (aq) + 2NaOH (aq) Na2A (aq) + 2H2O (l)
A 25.0 cm3 portion of 0.100 mol dm−3 sodium hydroxide solution required 12.80 cm3 of the solution of the diprotic acid for complete neutralisation.
What is the concentration of H2A in mol dm−3?
2.56 × 10−2
9.77 × 10−2
1.95 × 10−1
3.91 × 10−1
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In which compound is the oxidation number of nitrogen +5?
Ca(NO3)2
Mg3N2
N2O3
NaNO2
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Which reaction is not a redox reaction?
4KClO3 (s) → 3KClO4 (s) + KCl (s)
2HCl (aq) + Ba(OH)2 (aq) → BaCl2 (aq) + 2H2O (l)
Zn (s) + CuSO4 (aq) → ZnSO4 (aq) + Cu (s)
Cl2 (g) + H2O (l) → HCl (aq) + HClO (aq)
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In which reaction is the copper species acting as an oxidising agent?
Cu2+ + 2Ag → 2Ag+ + Cu
2Cu++ O2– → Cu2O
3Cu + O2 → Cu2O + CuO
Cu + Hg2+ → Hg + Cu2+
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Two half‐equations for a reaction are shown.
Cu → Cu2+ + 2e−
NO3− + 4H+ + 3e− → NO + 2H2O
What is the overall ionic equation for this reaction?
Cu + N+ 4H+→ Cu2+ + NO + 2H2O
2Cu + N+ 4H+→ 2Cu2+ + NO + 2H2O
3Cu + 2N+ 8H+→ 3Cu2+ + 2NO + 4H2O
6Cu + 2N+ 8H+→ 6Cu2+ + 2NO + 4H2O
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A titre of 13.25 cm3 was obtained using a 50 cm3 burette.
What is the percentage uncertainty in the titre?
[Each reading of the burette has an uncertainty of ±0.05 cm3]
±0.38%
±0.75%
±1.5%
±7.5%
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A pellet of sodium hydroxide has a mass of 0.700 g.
Some pellets were dissolved to make 350 cm3 of 0.25 mol dm–3 solution.
[Mr value: NaOH = 40]
How many pellets were dissolved?
4
5
8
125
25.0 cm3 of the sodium hydroxide solution prepared in (a) was placed in a conical flask and titrated with sulfuric acid.
2NaOH + H2SO4 → Na2SO4 + 2H2O
Calculate the number of moles of sulfuric acid that reacted.
0.0031
0.0063
0.013
0.044
colourless → pink
pink → colourless
orange → yellow
yellow → orange
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A group of students carry out an experiment to find the concentration of chlorine, Cl2 (aq), in a solution.
Excess potassium iodide solution is added to a 10.0 cm3 sample of the chlorine solution.
Cl2 (aq) + 2I− (aq) 2Cl− (aq) + I2 (aq)
The iodine produced is titrated with a solution of thiosulfate ions of known concentration, using starch indicator.
2S2O32- (aq) + I2 (aq) → S4O62- (aq) + 2I− (aq)
The concentration of the Cl2 (aq) is between 0.038 and 0.042 mol dm−3 .
What concentration of thiosulfate ions, in mol dm−3 , is required to give a titre of approximately 20 cm3 ?
0.010
0.020
0.040
0.080
What is the most suitable volume of 0.1 mol dm−3 potassium iodide solution, in cm3, to add to the 10.0 cm3 of chlorine solution?
7.6
8.0
8.4
10.0
What is the colour change at the end‐point of the titration?
colourless to pale yellow
pale yellow to colourless
colourless to blue‐black
blue‐black to colourless
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