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Standard XII

Chemistry

Heat of Formation

In the reacti...

Question

In the reaction $C S_{2} (l) + 3 O_{2} (g) \to C O_{2} (g) + 2 S O_{2} (g) Δ H = - 265 k c a l$ . 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 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
$C + O_{2} \to C O_{2}, Δ H = - 4 x$
$S + O_{2} \to S O_{2}, Δ H = - 2 \times 3 x$
$C + 2 S \to C S_{2}, Δ H = 26 k c a l / m o l$
$C S_{2} + 3 O_{2} \to C O_{2} + 2 S O_{2}, Δ H = - 265 k c a l$
$- 265 = - 4 x - 6 x - (+ 26) \Rightarrow x = (- 265 + 26) / 10 = - 23.9$
Enthalpy of $S O_{2} = - 3 \times 23.9 = - 71.7 k c a l / m o l$

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Similar questions

Q. 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

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are both negative and are in the ratio 4 : 3. The enthalpy of formation of

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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 $S O_{2}$ .

Q. 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

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In the reaction CS2(l)+3O2(g)→CO2(g)+2SO2(g)ΔH=−265kcal. 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/molC+O2→CO2 ,ΔH=−4xS+O2→SO2 ,ΔH=−2×3xC+2S→CS2 ,ΔH=26kcal/molCS2+3O2→CO2+2SO2 ,ΔH=−265kcal−265=−4x−6x−(+26)⇒x=(−265+26)/10=−23.9Enthalpy of SO2=−3×23.9=−71.7kcal/mol