How much heat (in kJ) is released when 15.0 L of CO at 85°C and 112 kPa reacts with 14.4 L of H2 at 75°C and 744 torr?
1 answer:
Heat energy released is - 31.4 kJ.
<u>Explanation:</u>
CO₍g₎ + 2H₂₍g₎ → CH₃OH₍l₎
Volume of CO, V ₍CO₎ = 15 L = 0.015 m³
Pressure = 112 kPa = 112,000 Pa
T= 85 ⁰C = 85 + 273 = 358 K
As per ideal gas law,
PV = nRT
n =
= 112000 × 0.015 / 8.314 × 358
n(CO) = 0.56 moles
Volume of H₂ = 14.4 L = 0.0144 m³
Pressure = 744 torr = 99191.84 Pa
T= 75⁰C + 273 K = 348 K
n(H₂) = 99191.84 ×0.0144 m³ / 8.314 ×348 K
= 0.49 moles of H₂
The above calculation shows that hydrogen is the limiting reagent.
n(CH₃OH) = n(H₂) /2
= 0.49/2 = 0.245 mol
ΔH₍rxn₎ = ΔH₍f₎ (CH₃OH) - ΔH₍f₎(CO)
= -238.6 -(-110.5)
= -128.1 kJ/mol
Now we have to multiply ΔH₍rxn₎ with the moles of methanol.
E = ΔH₍rxn₎ × n(CH₃OH) = -128.1 ×0.245
= - 31.4 kJ.
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