Consider the balanced equation below for a hypothetical reaction that takes place in a sealed 2 dm³ container at 300 K - NSC Physical Sciences - Question 6 - 2021 - Paper 2
Question 6
Consider the balanced equation below for a hypothetical reaction that takes place in a sealed 2 dm³ container at 300 K.
2P(g) + Q₂(g) ⇌ 2PQ(g)
Define the term chem... show full transcript
Worked Solution & Example Answer:Consider the balanced equation below for a hypothetical reaction that takes place in a sealed 2 dm³ container at 300 K - NSC Physical Sciences - Question 6 - 2021 - Paper 2
Step 1
Define the term chemical equilibrium.
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Answer
Chemical equilibrium is the state in a chemical reaction where the rate of the forward reaction equals the rate of the reverse reaction. At this point, the concentrations of reactants and products remain constant.
Step 2
Is the heat of the reaction (ΔH) POSITIVE or NEGATIVE?
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Answer
The heat of the reaction (ΔH) is NEGATIVE. This indicates that the reaction is exothermic.
Step 3
Use Le Chatelier's principle to explain the answer to QUESTION 6.2.1.
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Answer
According to Le Chatelier's principle, if the temperature of an exothermic reaction is increased, the equilibrium will shift to favor the endothermic direction to absorb the added heat. Therefore, the addition of heat to the system would favor the reverse reaction, which is consistent with ΔH being negative.
Step 4
Calculate the equilibrium constant at 350 K.
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Answer
To calculate the equilibrium constant (K) at 350 K, we use the formula:
K=[P]2[Q2][PQ]2
From the equilibrium amounts:
P = 1.2 mol
Q₂ = 0.8 mol
PQ = 3.2 mol
Substituting these values into the equation:
K=(1.2)2(0.8)(3.2)2=1.44×0.810.24=1.15210.24=8.89
Thus, the equilibrium constant at 350 K is approximately 8.89.
Step 5
How will the equilibrium constant calculated in QUESTION 6.2.3 be affected when the volume of the container is decreased at constant temperature?
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Answer
The equilibrium constant remains the SAME when the volume of the container is decreased at constant temperature. This is because the equilibrium constant is only affected by changes in temperature.
Step 6
The yield of PQ(g)
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Answer
The yield of PQ(g) will INCREASE because adding more Q₂(g) shifts the equilibrium position to the right, producing more products.
Step 7
Number of moles of P(g)
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The number of moles of P(g) will DECREASE. This occurs because P(g) is a reactant in the equilibrium reaction; as more Q₂(g) is added, P(g) is consumed to form more PQ(g).
