CO₂ is added to 1.00 L of pure water at 25°C in a pressurised bottle. The pressure of CO₂ above the water was raised to 3.00 atm and the gaseous CO₂ came to equilibrium with the CO₂ dissolved in the water. At equilibrium, the mass of CO₂ dissolved in the water was 5.00 g. a. The equilibrium constant for this reaction, in atm M⁻¹, can be written as: $$K_c = \frac{p(CO_2, g)}{[CO_2 (aq)]}$$ where $p(CO_2)$ represents the pressure of CO₂. Calculate the value of this equilibrium constant at 25°C.

SSCE VCE Chemistry Extent of Chemical Reactions: CO₂ is added to 1.00 L of pure w

CO₂ is added to 1.00 L of pure water at 25°C in a pressurised bottle - VCE - SSCE Chemistry - Question 6 - 2004 - Paper 1

Question 6

CO₂ is added to 1.00 L of pure water at 25°C in a pressurised bottle. The pressure of CO₂ above the water was raised to 3.00 atm and the gaseous CO₂ came to equilibr... show full transcript

Worked Solution & Example Answer:CO₂ is added to 1.00 L of pure water at 25°C in a pressurised bottle - VCE - SSCE Chemistry - Question 6 - 2004 - Paper 1

Step 1

Calculate the number of moles of CO₂

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Answer

To find the number of moles of CO₂ dissolved, we use the molar mass of CO₂. The molar mass of CO₂ is approximately 44.01 g/mol.

The number of moles (n) can be calculated as follows:

$n(CO_2) = \frac{5.00 \, g}{44.01 \, g/mol} \approx 0.1136 \, mol$

Step 2

Determine the concentration of CO₂ in the solution

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Answer

Since the volume of the solution is 1.00 L, the concentration [CO₂(aq)] can be calculated:

$[CO_2(aq)] = \frac{n(CO_2)}{V} = \frac{0.1136 \, mol}{1.00 \, L} = 0.1136 \, M$

Step 3

Calculate the pressure of CO₂

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Answer

Using the ideal gas law to find the pressure of CO₂:

$p(CO_2) = \frac{n \cdot R \cdot T}{V}$

Where:

$n = 0.1136 \, mol$
$R = 0.0821 \, L \, atm \, K^{-1} \, mol^{-1}$
$T = 25 + 273 = 298 \, K$
$V = 1.00 \, L$

Calculating:

$p(CO_2) = \frac{0.1136 \, mol \cdot 0.0821 \, L \, atm \, K^{-1} \, mol^{-1} \cdot 298 \, K}{1.00 \, L} \approx 2.78 \, atm$

Step 4

Calculate the equilibrium constant Kc

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Answer

Now, substituting the values into the expression for the equilibrium constant:

$K_c = \frac{p(CO_2, g)}{[CO_2(aq)]} = \frac{2.78 \, atm}{0.1136 \, M} \approx 24.5 \, atm \, M^{-1}$

Thus, the value of the equilibrium constant at 25°C is approximately 24.5 atm M⁻¹.

CO₂ is added to 1.00 L of pure water at 25°C in a pressurised bottle - VCE - SSCE Chemistry - Question 6 - 2004 - Paper 1

Worked Solution & Example Answer:CO₂ is added to 1.00 L of pure water at 25°C in a pressurised bottle - VCE - SSCE Chemistry - Question 6 - 2004 - Paper 1

Calculate the number of moles of CO₂

Determine the concentration of CO₂ in the solution

Calculate the pressure of CO₂

Calculate the equilibrium constant Kc

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