Which is the correct Kc expression for the reaction between hydrogen and fluorine?
H2 (g) + F2 (g) ⇌ 2HF (g)
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Syllabus Edition
First teaching 2014
Last exams 2024
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17.1 The Equilibrium Law
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17.1 The Equilibrium Law
Which is the correct Kc expression for the reaction between hydrogen and fluorine?
H2 (g) + F2 (g) ⇌ 2HF (g)
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The Kc expression for the following reaction between hydrogen and iodine is shown
H2 (g) + I2 (g) ⇌ 2HI (g)
At equilibrium there were 0.234 moles of HI, 0.150 moles of H2 and 0.025 moles of I2.
Which is the correct Kc expression for the reaction between hydrogen and fluorine?
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Nitrosyl chloride decomposes into nitrogen monoxide and chlorine according to the following equation. The forward reaction is endothermic
2NOCl (g) ⇌ 2NO (g) + Cl2 (g)
Which change in condition would change the value for Kc?
Decreasing the pressure
Adding a catalyst
Increasing the temperature
Increasing the pressure
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Which of the following rows correctly describes Kc and ΔG for a reaction where the products are favoured?
Kc | ΔG | |
A. | > 1 | < 1 |
B. | > 1 | < 0 |
C. | > 0 | > 0 |
D. | > 0 | > 1 |
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At 300 K, iron oxidises according to the following equation:
2Fe (s) + O2 (g) ⇌ Fe2O3 (s)
The standard Gibbs free energy change for this reaction is -743.05 kJ mol-1.
The quantitative relationship between the standard Gibbs free energy change, temperature and the equilibrium constant is:
ΔG = –RT ln K
Which expression is a correct step towards calculating the value of the equilibrium constant? (R = 8.31 J K–1 mol–1)
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When gaseous dinitrogen pentoxide, N2O5 (g), decomposes at 358 K, the following equilibrium is established:
2N2O5 (g) ⇌ 4NO2 (g) + O2 (g)
2.0 mol of N2O5 (g) were placed in a 1.0 dm3 container and allowed to reach equilibrium. At equilibrium 1.0 mol of N2O5 (g) were present. What is the value of Kc?
0.125
1
2
8
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Consider the following reversible reaction:
3O2 (g) ⇌ 2O3 (g)
What is the value of Kc when the equilibrium concentrations are [O2] = 4.0 mol dm-3 and [O3] = 4.0 mol dm-3 ?
0.25
4
16
64
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Which of the following will shift the position of equilibrium to the right in the reaction shown?
2N2O5 (g) ⇌ 4NO2 (g) + O2 (g) ΔH = +219.2 kJ
I and II only
I and III only
II and III only
I, II and III
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Hydrogen iodide decomposes to form hydrogen and iodine vapour.
2HI (g) ⇌ H2 (g) + I2 (g)
What is the effect of decreasing the volume of the equilibrium mixture at constant temperature?
The amount of H2 (g) remains the same but its concentration decreases
The forward reaction is favoured
The backward reaction is favoured
The value of Kc remains unchanged
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A mixture of 0.40 mol of SO2 (g) and 0.40 mol of O2 (g) was placed in a 1 dm3 container. The following equilibrium took place:
2SO2 (g) + O2 (g) ⇌ 2SO3 (g)
At equilibrium the mixture contained 0.25 mol of O2 (g) .How many moles of SO2 (g) and SO3 (g) were present at equilibrium?
|
SO2 (g) / mol |
SO3 (g) / mol |
A |
0.25 |
0.15 |
B |
0.30 |
0.15 |
C |
0.10 |
0.30 |
D |
0.25 |
0.30 |
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The Haber process is a key step in the manufacture of fertilisers:
N2 (g) + 3H2 (g) 2NH3 (g) ΔH = -ve
Which is correct about the effect of increasing temperature for this reaction?
Effect on equilibrium position | Effect on Kc | |
A. | Shifts left | No change |
B. | Shifts right | No change |
C. | Shifts right | Increase |
D. | Shifts left | Decrease |
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Which equation represents a reaction where the number of moles alone can not be used to calculate the value of Kc?
CH3CH2OH (aq) + CH3COOH (aq) CH3CH2OCOCH3 (aq) + H2O (l)
H2 (g) + I2 (g) 2HI (g)
2SO2 (g) + O2 (g) 2SO3 (g)
N2 (g) + O2 (g) 2NO (g)
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When 0.20 mol NO, 0.08 mol H2 and 0.10 mol of H2O are placed in a 1.0 dm3 flask, the following equilibrium is established:
2NO (g) + 2H2 (g) N2 (g) + 2H2O (g)
At equilibrium, the concentration of H2 (g) was found to be 0.02 mol dm-3.
What is the correct calculation to work out Kc?
Kc =
Kc =
Kc =
Kc =
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Nitrogen dioxide can form a dimer that can also break back down again as part of a reversible reaction:
N2O4 (g) NO2 (g) ΔH = +ve
The reaction reaches an equilibrium at temperature T, where Kc = 1
What is true for a higher temperature, T2?
Kc value | ΔGθ value | |
A. | Increases | Increases |
B. | Decreases | Increases |
C. | Decreases | Decreases |
D. | Increases | Decreases |
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Which would be the correct way to plot a graph and then calculate ΔGθ from experimental data of Kc and temperature values?
ΔGθ = -RT ln K
y-axis | x-axis | ΔGθ = | |
A. | 1 / T | ln K | -R x gradient |
B. | ln K | 1 / T | -R x gradient |
C. | ln K | 1 / T | R / gradient |
D. | 1 / T | ln K | R / gradient |
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