0.100 mol of CaCO3 and 0.100 mol CaO are placed in an 10.0 L evacuated container and heated to 385 K. When equilibrium is reached the pressure of CO2 is 0.220 atm. 0.230 atm of CO2 is added, while keeping the temperature constant and the system is allowed to reach again equilibrium. What will be the final mass of CaCO3

Respuesta :

The given 0.100 moles of CaCO₃ and CaO and the addition of 0.230 atm

of CO₂ gives a final mass of CaCO₃ of approximately 38.79 grams.

How can the mass of CaCO₃ at equilibrium be found?

Given parameters;

Number of moles of CaCO₃ = 0.100 mol

Volume of the container, V = 10.0 L

Number of moles of CaO = 0.100 mol

Temperature of the reaction, T = 385 K

Pressure of CO₂ produced, P = 0.220 atm

Pressure of CO₂ added = 0.230 atm

Required;

Mass of CaCO₃ after equilibrium is reestablished.

Solution;

Equilibrium constant for the partial pressure, [tex]\mathbf{K_p }= P_{CO_2}[/tex]

Chemical reaction; CaCO₃(s) ⇄ CaO(s) + CO₂(g)

[tex]Number \ of \ moles, \ n =\mathbf{ \dfrac{P\cdot V}{R \cdot T}}[/tex]

[tex]Moles \ of \ CO_2 \ produced = \dfrac{0.22 \ atm \times 10 \, L}{0.08206 \, L\cdot atm/\left( mol\cdot K\right) \times 385 \, K} \approx\mathbf{ 0.0696 \, moles}[/tex]

[tex]Equilibrium\ constant,\ K_c = [CO_2] \approx \dfrac{0.0696 \, moles}{10 \, L} = 0.00696 \, M[/tex]

Moles of CaCO₃ after the reaction ≈ (0.1 - 0.0696) moles = 0.304 moles

When 0.230 atm CO₂ is added, we have;

Pressure of CO₂ = 0.220 atm + 0.230 atm = 0.450 atm

Which gives;

[tex]n_{CO_2} = \dfrac{0.45 \ atm \times 10 \, L}{0.08206 \, L\cdot atm/\left( mol\cdot K\right) \times 385 \, K} \approx \mathbf{0.1532 \, moles}[/tex]

The number of moles of moles of CO₂ that react with CaO to produce

(the same number of moles of) CaCO₃, x, is found as follows;

[tex]0.00696 \ moles\approx \mathbf{\dfrac{0.1532 - x}{10} \ mol/L}[/tex]

10 × 0.00696 moles ≈ 0.1532 - x

0.1532 - 0.0696 = 0.0836 ≈ x

The final number of moles of CaCO₃ when the system reaches

equilibrium again is therefore;

New [tex]\mathbf{n_{CaCO_3}}[/tex] at equilibrium = (0.304 + 0.0836) moles = 0.3876 moles

Molar mass of CaCO₃ = 100.0869 g/mol

Final mass of CaCO₃ = 100.0869 g/mol × 0.3876 moles ≈ 38.79 grams

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