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Standard XII

Chemistry

Heat of Formation

In the reacti...

Question

In the reaction $C S_{2} (l) + 3 O_{2} (g) \to C O_{2} (g) + 2 S O_{2} (g) △ H = - 265 k c a l$
The enthalpies of formation of $C O_{2}$ and $S O_{2}$ are both negative and are in the ratio 4 : 3. The enthalpy of formation of $C S_{2}$ is + 26 kcal/mol. Calculate the enthalpy of formation of $S O_{2} .$

- 90 kcal/mol

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-52 kcal/mol

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-78 kcal/mol

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-71.7 kcal/mol

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Solution

The correct option is D -71.7 kcal/mol
$C S_{2} (l) + 3 O_{2} (g) \to C O_{2} (g) + 2 S O_{2} (g) △ H = - 265 k c a l$
Let $△ H_{f} (C O_{2}, g) = - 4 x a n d △ H_{f} (S O_{2}, g) = - 3 x$
$△ H_{r e a c t i o n} = △ H_{f} (C O_{2}, g) + 2 △ H_{f} (S O_{2}, g) - △ H_{f} (C S_{2}, l)$
$- 265 = - 4 x - 6 x - 26$
$x = + 23.9$
$∴ △ H_{f} (S O_{2}, g) = - 3 x = - 71.7 k c a l / m o l .$

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In the reaction

$C S_{2} (l) + 3 O_{2} (g) \to C O_{2} (g) + 2 S O_{2} (g) Δ H = - 265 k c a l$

The enthalpies of formation of $C O_{2}$ and $S O_{2}$ are both negative and are in the ratio 4 : 3. The enthalpy of formation of $C S_{2}$ is $+ 26 k c a l / m o l$ . Calculate the enthalpy of formation of $S O_{2}$ .

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Heat of Formation

Standard XII Chemistry

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In the reaction CS2 (l)+3O2 (g)→CO2 (g)+2SO2 (g) △H=−265 kcal The enthalpies of formation of CO2 and SO2 are both negative and are in the ratio 4 : 3. The enthalpy of formation of CS2 is + 26 kcal/mol. Calculate the enthalpy of formation of SO2.

The correct option is D -71.7 kcal/molCS2 (l)+3O2 (g)→CO2 (g)+2SO2 (g) △H=−265 kcal Let △Hf(CO2,g)=−4x and △Hf(SO2,g)=−3x △Hreaction=△Hf(CO2,g)+2 △Hf(SO2,g)−△Hf(CS2,l) −265=−4x−6x−26 x=+23.9 ∴ △Hf(SO2,g)=−3x=−71.7 kcal/mol.