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Hess' Law

Given that th...

Question

Given that the bond energies of $: N \equiv N$ is $946$ kJ $m o l^{- 1}$ $H - H$ is $435$ kJ $m o l^{- 1}$ , $N - N$ is $159$ kJ $m o l^{- 1}$ , and $N - H$ is $389$ kJ $m o l^{- 1}$ , the heat of formation of hydrazine in the gas phase in kJ $m o l^{- 1}$ is:

833

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101

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334

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1264

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Solution

The correct option is B $101$
$N_{2} + 2 H_{2} \to N_{2} H_{4}$

$Δ H_{f} = B . E (r e a c t a n t s) - B . E (p r o d u c t s)$

$Δ H_{f} = 946 + 2 \times 435 - (4 \times 389 + 159) = 101 k J / m o l$

Hence option $B$ is correct.

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Similar questions

N - H, H - H, N \equiv N

m o l^{- 1}

m o l^{- 1}

m o l^{- 1}

Δ H^{o}

N_{2} H_{4} (g)

N_{2} (g) + 2 H_{2} (g) \to N_{2} H_{4} (g)

Δ_{f} H^{o}

N_{2} H_{4} (g)

N - N = 159 {kJ mol}^{- 1}; H - H = 436 {kJ mol}^{- 1}

N \equiv N = 941 {kJ mol}^{- 1}; N - H = 398 {kJ mol}^{- 1}

(B . E .)

Δ_{f} H^{\circ}

N_{2} H_{4} (g)

N - N = 159 {kJ mol}^{- 1}; H - H = 436 {kJ mol}^{- 1} N \equiv N = 941 {kJ mol}^{- 1}; N - H = 398 {kJ mol}^{- 1}

Δ_{f} H^{0}

N_{2} H_{4} (g)

N - N = 159 k J m o l^{- 1}; H - H = 436 k J m o l^{- 1}

N \equiv N = 941 k J m o l^{- 1}; {N - H = 398 k J m o l}^{- 1}

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