Nitrogen and hydrogen were mixed in a 1:3 mole ratio and left to reach equilibrium in a flask at a temperature of 550 K. The equation for the reaction between nitrogen and hydrogen is shown. N2(g) + 3H2(g) ⇌ 2NH3(g) When equilibrium was reached, the total pressure in the flask was 150 kPa and the mole fraction of NH3(g) in the mixture was 0.80. Calculate the partial pressure of each gas in this equilibrium mixture. Partial pressure of nitrogen __________ kPa Partial pressure of hydrogen __________ kPa Partial pressure of ammonia __________ kPa Give an expression for the equilibrium constant (Kc) for this reaction. Kc = __________ In a different equilibrium mixture, under different conditions, the partial pressures of the gases are shown in Table 2. Table 2 Gas Partial pressure / kPa N2 1.20 × 10^2 H2 1.50 × 10^2 NH3 1.10 × 10^2 Calculate the value of the equilibrium constant (Kc) for this reaction and give its units. Kc = __________ Units = __________ The enthalpy change for the reaction is -92 kJ mol-1. State the effect, if any, of an increase in temperature on the value of Kc for this reaction. Justify your answer. Effect on Kc __________ Justification __________

A-Level AQA Chemistry The Mole, Avogadro & The Ideal Gas Equation: Nitrogen and hydrogen were mixed

Nitrogen and hydrogen were mixed in a 1:3 mole ratio and left to reach equilibrium in a flask at a temperature of 550 K - AQA - A-Level Chemistry - Question 2 - 2018 - Paper 1

Question 2

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Nitrogen and hydrogen were mixed in a 1:3 mole ratio and left to reach equilibrium in a flask at a temperature of 550 K. The equation for the reaction between nitrog... show full transcript

Worked Solution & Example Answer:Nitrogen and hydrogen were mixed in a 1:3 mole ratio and left to reach equilibrium in a flask at a temperature of 550 K - AQA - A-Level Chemistry - Question 2 - 2018 - Paper 1

Step 1

Calculate the partial pressure of nitrogen

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Answer

Given that the mole fraction of NH3 is 0.80, we can find the mole fractions of the other gases. Since the total pressure is 150 kPa, we can express the mole fraction of hydrogen as follows:

Let the mole fraction of H2 be denoted as x:

Mole fraction of nitrogen = 1 - 0.80 - x

Using the fact that the total mole fraction sums to 1, we have:

0.20 - x = mole fraction of nitrogen

Calculating the partial pressure of nitrogen:

Partial pressure of N2 = (mole fraction of N2) × (total pressure) Partial pressure of N2 = (0.20 - x) × 150 kPa

At equilibrium, using the stoichiometry of the reaction, we find: Partial pressure of NH3 = 0.80 × 150 kPa = 120 kPa Substituting: Partial pressure of H2 = P (total) - P (NH3) - P (N2) This can be solved accordingly.

Step 2

Calculate the partial pressure of hydrogen

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Answer

Partial pressure of H2 can be calculated using the relationship derived from mole fractions: Partial pressure of H2 = (mole fraction of H2) × (total pressure) Using a ratio from the stoichiometry: Partial pressure of hydrogen = 0.75 × 150 kPa = 112.5 kPa.

Step 3

Calculate the partial pressure of ammonia

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Answer

Partial pressure of NH3 = 0.80 × 150 kPa = 120 kPa.

Step 4

Give an expression for the equilibrium constant (Kc) for this reaction.

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Answer

Kc = \frac{(P_{NH3})^2}{(P_{N2}) (P_{H2})^3}

Step 5

Calculate the value of the equilibrium constant (Kc) for this reaction and give its units.

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Answer

Given the partial pressures from Table 2:

P(N2) = 1.20 × 10² kPa
P(H2) = 1.50 × 10² kPa
P(NH3) = 1.10 × 10² kPa Using the formula:

Kc = \frac{(1.10 × 10^2)^2}{(1.20 × 10^2) (1.50 × 10^2)^3}

Calculating gives Kc in units of (kPa)^{-2}.

Step 6

State the effect of an increase in temperature on the value of Kc for this reaction.

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Answer

Effect on Kc: Decrease.

Justification: Since the reaction is exothermic, an increase in temperature shifts the equilibrium to favor reactants, hence decreasing Kc.

Nitrogen and hydrogen were mixed in a 1:3 mole ratio and left to reach equilibrium in a flask at a temperature of 550 K - AQA - A-Level Chemistry - Question 2 - 2018 - Paper 1

Worked Solution & Example Answer:Nitrogen and hydrogen were mixed in a 1:3 mole ratio and left to reach equilibrium in a flask at a temperature of 550 K - AQA - A-Level Chemistry - Question 2 - 2018 - Paper 1

Calculate the partial pressure of nitrogen

Calculate the partial pressure of hydrogen

Calculate the partial pressure of ammonia

Give an expression for the equilibrium constant (Kc) for this reaction.

Calculate the value of the equilibrium constant (Kc) for this reaction and give its units.

State the effect of an increase in temperature on the value of Kc for this reaction.

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