Which row shows the correct observation for the reactions of [Cu(H2O)6]2+ (aq)?
| Substance added | Observation |
A | Na2CO3 (aq) | Blue precipitate which does not redissolve and fizzing |
B | NH3 (aq) | Blue precipitate which redissolves to form a deep-blue solution with excess NH3 (aq) |
C | NaOH (aq) | Blue precipitate which redissolves to form a deep-blue solution with excess NaOH (aq) |
D | HCl (aq) | Blue precipitate initially which does not redissolve with excess HCl (aq) |
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A 20.00 cm3 of sodium sulfate(IV), Na2SO3, was titrated with 36.30 cm3 of 0.51 mol dm-3 of potassium dichromate, K2Cr2O7, in the presence of concentrated sulfuric acid, H2SO4.
3SO32- (aq) + Cr2O72- (aq) + 8H+ (aq) → 2Cr3+ (aq) + 3SO42- (aq) + 4H2O (l)
What is the number of moles of sodium sulfate(IV), Na2SO3?
0.06 moles
0.02 moles
0.03 moles
0.05 moles
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Zinc metal is added to a solution containing VO2+ ions.
The table shows some electrode half-equations and their standard electrode potentials
Electrode half-equation | EӨ / V |
Zn2+ (aq) + 2e- ⇌ Zn (s) | -0.76 |
V3+ (aq) + e- ⇌ V2+ (aq) | -0.26 |
VO2+ (aq) + 2H+ (aq) + e- ⇌ H2O (l) + V3+ (aq) | +0.34 |
VO2+ (aq) + 2H+ (aq) + e- ⇌ H2O (l) + VO2+ (aq) | +1.00 |
Which of the following is not correct?
The oxidation number of vanadium in VO2+ is +5
Zinc will oxidise V2+ to V3+
Zinc can reduce VO2+ to VO2+
The solution will change colour
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Which of the following shows a rate curve for a reaction in autocatalysis?
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A student performed the following chemical tests to identify an unknown solution.
The student’s results are shown in the table.
Chemical Test | Result |
Addition of HNO3 (aq) and AgNO3 (aq) followed dilute NH3 (aq) | Cream precipitate formed which was insoluble in dilute ammonia |
Addition of Na2CO3 (aq) | Orange / brown precipitate and effervescence |
What is the identity of the unknown solution?
FeBr3
FeCl3
FeCl2
FeBr2
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Which of the following observations is correct when excess sodium carbonate, Na2CO3(aq), is added to separate samples of Fe2+ and Fe3+ ions in an aqueous solution?
| Fe2+ | Fe3+ |
A | Brown ppt and bubbles of gas | Green ppt |
B | Green ppt | Brown ppt |
C | Brown ppt | Green ppt and bubbles of gas |
D | Green ppt | Brown ppt and bubbles of gas |
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The following equation shows the oxidation of sodium nitrate(III) solution to sodium nitrate(V) solution by potassium permanganate solution
2MnO4- (aq) + 6H+ (aq) + 5NO2- (aq) → 2Mn2+ (aq) + 5NO3- (aq) + 3H2O (l)
What volume of 0.06 mol dm-3 sodium nitrate(III) solution was required for the first permanent colour change when added to 25.00 cm3 of 0.03 mol dm-3 potassium permanganate solution?
12.50 cm3
0.03125 cm3
0.005 dm3
31.25 cm3
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Which of the following is not correct when excess of ammonia is added to a solution of copper ions?
[Cu(NH3)4(H2O)2]2+ (aq) is formed
A dark blue solution is observed
A blue precipitate of Cu(OH)2(H2O)4 is formed
4 water molecules are replaced by 4 ammonia molecules
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The table shows some electrode half-equations and their standard electrode potentials.
Electrode half-equation | EӨ / V |
Zn2+ (aq) + 2e- ⇌ Zn (s) | -0.76 |
V3+ (aq) + e- ⇌ V2+ (aq) | -0.26 |
Sn2+ (aq) + 2e- ⇌ Sn (s) | -0.14 |
VO2+ (aq) + 2H+ (aq) + e- ⇌ H2O (l) + V3+ (aq) | +0.34 |
NO3- (aq) + 4H+ (aq) + 3e- ⇌ NO (g) + 2H2O (l) | +0.96 |
VO2+ (aq) + 2H+ (aq) + e- ⇌ H2O (l) + VO2+ (aq) | +1.00 |
Identify the chemical species that will be able to oxidise vanadium(II) to vanadium(IV).
Sn2+ (aq)
NO3- (aq)
Zn2+ (aq)
NO (g)
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The overall equation for the reaction between manganate ions and ethanedioate ions is represented by
2MnO4- (aq) + 5C2O42- (aq) + 16H+ (aq) → 2Mn2+ (aq) + 10CO2 (g) + 8H2O (l)
Which of the following is correct?
The initial reaction has a low activation energy
Carbon C2O42- is oxidised from +4 to +3
The rate of reaction increases when Mn2+ ions are produced
The rate of reaction increases when Mn3+ ions are produced
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The diagram shows a reaction sequence involving the compounds of a transition metal:
Which reaction(s) produce gases?
D → A and D → C
D → C and B → C
Only D → A
A → B and B → C
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Three elements from Period 3, P, Q and R, were separately heated in air and the pH of the oxides was tested.
P burns with a pale blue flame. The oxide of Q is almost insoluble in water, but reacts with hydrochloric acid. R forms an oxide which contains 60% of the element by mass.
What is the order of increasing pH of the three oxides?
R < Q < P
P < Q < R
Q < P < R
R < P < Q
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A student used a colorimeter to measure the concentration of a coloured reactant against time and plotted the results on a graph shown below.
Which statement is true?
The product is colourless
The rate of reaction decreases during the reaction
The activation energy decreases during the reaction
The rate constant does not vary during the reaction
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A 1.800 g iron supplement tablet was dissolved in sulfuric acid and converted to Fe2+. This was titrated against KMnO4 and required 26.50 cm3 of 0.100 mol dm-3 for complete reaction.
What is the percentage by mass of iron in the iron supplement tablet?
41.1%
1.64%
0.739%
8.22%
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Substance M is an inorganic double salt of a transition metal. It undergoes the following reactions:
Test | Observation |
Addition of dilute H2SO4 | No visible change |
Addition of dilute NaOH and warming | Green gelatinous precipitate and pungent gas given off which turns red litmus blue |
Addition of excess NaOH | Green gelatinous precipitate redissolves |
What could be the identity of M?
FeSO4
(NH4)2Fe(SO4)2
NH4Fe(SO4)2
NH4Cr(SO4)2
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