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Standard XII

Chemistry

Heat of Reaction

When 2 mole...

Question

When $2$ mole of $C_{2} H_{6}$ are completely burnt, $3129 k J$ of heat is liberated. Calculate the heat of formation of $C_{2} H_{6}$ . $Δ H_{f}$ for ${C O}_{2}$ and $H_{2} O$ are $- 395 k J$ and $- 286 k J$ respectively.

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Solution

The equation for the combustion of $C_{2} H_{5}$ is:
$C_{2} H_{6} + 7 O_{2} = 4 {C O}_{2} + 6 H_{2} O; Δ H = - 3129 k J$
$Δ H^{o} = Δ H_{f (p r o d u c t s)}^{o} - Δ H_{f (r e a c t a n t s)}$
$= [4 \times Δ H_{({C O}_{2})}^{o} + 6 \times Δ H_{(H_{2} O)}^{o}] - [2 \times Δ H_{(C_{2} H_{6})}^{o} + 7 \times Δ H_{(O_{2})}^{o}]$
$- 3129 = [4 \times (- 395) + 6 \times (- 286)] - [2 \times Δ H_{(C_{2} H_{6})} + 7 \times 0]$
or $2 \times Δ H_{(C_{2} H_{6})} = - 167$
$Δ H_{(C_{2} H_{6})} = - \frac{167}{2} = - 83.5 k J$

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Similar questions

Q. When

2

moles of

C_{2} H_{6}

are completely burnt,

3120 k J

of heat is liberated. Calculate the heat of formation

Δ H_{f}^{o}

for

C_{2} H_{6}

Given:

Δ H_{f}^{o}

for

{C O}_{2} (g)

and

H_{2} O (l)

are

- 395

and

- 286 k J

respectively.

When 2 mole of $C_{2} H_{6}$ are completely burnt, 3129 KJ of heat is liberated. Calculate the heat of formation of $C_{2} H_{6} . △ H_{f}$ for $C O_{2} & H_{2} O$ are -395 KJ and -286 KJ respectively.

Q. When

2

moles of

C_{2} H_{6}

are completely burnt

3120 k J

of heat is liberated. Calculate the heat of formation,

△ H_{f}^{\circ}

for

C_{2} H_{6}

. Given

△ H_{f}^{0}

for

C O_{2} (g)

and

H_{2} O (l)

are

- 395

and

- 286 k J

respectively.

20 m l

of a mixture of

C_{2} H_{4}

and

C_{2} H_{6}

gases is burnt completely in excess of

O_{2}

. The volume of

C O_{2}

gas formed is:

Q. When

2

mole of

C_{2} H_{4}

is completely burnt then

2648

kJ heat is liberated and

Δ H c

C i s - 394 k J

and

Δ H f

C_{2} H_{4} i s - 52 K J

Calculate

Δ H c

for hydrogen.

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When 2 mole of C2H6 are completely burnt, 3129kJ of heat is liberated. Calculate the heat of formation of C2H6. ΔHf for CO2 and H2O are −395 kJ and −286 kJ respectively.

The equation for the combustion of C2H5 is:C2H6+7O2=4CO2+6H2O;ΔH=−3129 kJΔHo=ΔHof(products)−ΔHf(reactants)=[4×ΔHo(CO2)+6×ΔHo(H2O)]−[2×ΔHo(C2H6)+7×ΔHo(O2)]−3129=[4×(−395)+6×(−286)]−[2×ΔH(C2H6)+7×0]or 2×ΔH(C2H6)=−167ΔH(C2H6)=−1672=−83.5 kJ

When $2$ mole of $C_{2} H_{6}$ are completely burnt, $3129 k J$ of heat is liberated. Calculate the heat of formation of $C_{2} H_{6}$ . $Δ H_{f}$ for ${C O}_{2}$ and $H_{2} O$ are $- 395 k J$ and $- 286 k J$ respectively.