The heat of formation of CO $_{(g)}$ and CO $_{2 (g)}$ are $Δ$ H =- 110 and $Δ$ H = -393 kJ.mol $^{- 1}$ respectively. What is the heat of reaction ( $Δ$ H ) (in kJ.mol $^{- 1}$ ) for the following reaction $C O + \frac{1}{2} O_{2} \to C O_{2}$ ?

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The enthalpies of decomposition of methane (CH4) and ethane (C2H6) are 400 and 670 kJ.mol−1, respectively. The ΔHC−C in kJ.mol−1 is:

The correct option is B 70Given that,CH4(g)→C(g)+4H(g);ΔH=400C2H6(g)→2C(g)+6H(g);ΔH=670Again,ΔHC−H=100ΔHC−C+6ΔHC−H=ΔHC−C+6×100=670∴ΔHC−C=70

The enthalpies of decomposition of methane $(C H_{4})$ and ethane $(C_{2} H_{6})$ are 400 and 670 $k J . m o l^{- 1}$ , respectively. The $Δ H_{C - C}$ in $k J . m o l^{- 1}$ is:

The correct option is B $70$
Given that,
$C H_{4} (g) \to C (g) + 4 H (g); Δ H = 400$
$C_{2} H_{6} (g) \to 2 C (g) + 6 H (g); Δ H = 670$
Again,
$Δ H_{C - H} = 100$
$Δ H_{C - C} + 6 Δ H_{C - H} = Δ H_{C - C} + 6 \times 100 = 670$
$∴ Δ H_{C - C} = 70$