Enthalpy of C...

Enthalpy of Combustion

Trending Questions

Why do bonds release energy?

Q. The heat of combustion of sucrose

(C_{12} H_{22} O_{11})

- 5.65 \times 10^{3} k J

. If complete combustion of

1.0 k g

sucrose is done, heat evloved will be:

$1.65 \times 10^{4} k J$
$5.65 \times 10^{3} k J$
$7.38 \times 10^{5} k J$
$3.51 \times 10^{5} k J$

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Q. In the combustion of

2 g

of methane,

25 k c a l

heat is liberated. Find the molar heat of combustion of methane.

$100 k c a l$
$200 k c a l$
$75 k c a l$
$150 k c a l$

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Q. When

1.0 g

of oxalic acid

(H_{2} C_{2} O_{4})

is burned in a bomb calorimeter whose heat capacity is

8.75 k J / K

, the temperature increases by

0.312 K

. The enthalpy of combustion of oxalic acid at

27^{o} C

is:

$- 300.7 k J / m o l$
$- 280.452 k J / m o l$
$- 241.947 k J / m o l$
None of these

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Q. The combustion of hydrogen-oxygen mixture is used to produce very high temperatures

(\approx 2500^{o} C)

needed for certain types of welding operations.

H_{2} (g) + \frac{1}{2} O_{2} (g) \to H_{2} O (g); △ H = - 230.9 k J

Quantity of heat, (in kJ) evolved when a 200 g mixture containing equal parts of

H_{2}

and

O_{2}

by mass is burned, is

$2.72 \times 10^{3} k J$
$1.36 \times 10^{3} k J$
$1.44 \times 10^{3} k J$
$4.3524 \times 10^{4} k J$

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How will you provide the following information in a chemical equation?

Evolution of heat

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Q. Efficiency of a fuel is based on it's :

Specific heat
Calorific value
Cost
Ignition temperature

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The standard heat of combustion of $A l$ is $- 837.8 k J m o l^{- 1}$ $25^{\circ} C$ which of the following releases $250 k c a l$ of heat?

The reaction of $0.624 m o l$ of $A l$
The formation of $0.624 m o l$ of $A l_{2} O_{3}$
The reaction of $0.312 m o l$ of $A l$
The formation of $0.150 m o l$ of $A l_{2} O_{3}$

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Q. The standard enthalpy of formation of octane

(C_{8} H_{18})

- 250 k J / m o l

. Calculate the enthalpy of combustion of

C_{8} H_{18}

.
Given : enthalpy of formation of

C O_{2} (g)

and

H_{2} O (l)

are

- 394 k J / m o l

and

- 286 k J / m o l

respectively:

$- 5200 k J / m o l$
$- 5726 k J / m o l$
$- 5476 k J / m o l$
$- 5310 k J / m o l$

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Q. (i) Cis - 2 - butene

\to

trans-2-butene,

△ H_{1}

(ii) Cis - 2 - butene

\to

1 - butene,

△ H_{2}

(iii) Trans-2-butene is more stable than cis - 2 - butene.
(iv) Enthalpy of combustion of 1 - butene,

△ H = - 649.8 k c a l / m o l

(v)

9 △ H_{1} + 5 △ H_{2} = 0

(vi) Enthalpy of combustion of trans 2 - butene,

△ H = - 647.0 k c a l / m o l .

The value of

△ H_{1}

and

△ H_{2}

in kcal/mol are

- 1.0, 1.8
1.8, -1.0
-5, 9
-2, 3.6

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Q. The standard enthalpy of combustion at

25^{o} C

of hydrogen, cyclohexene (

C_{6} H_{10}

) and cyclohexane (

C_{6} H_{12}

) are

- 241, - 3800 a n d - 3920 k J m o l^{- 1}

respectively. Calculate the heat of hydrogenation of cyclohexene ( in

k J m o l^{- 1}

)

$- 121$
$+ 121$
$+ 221$
$- 221$

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Q. The enthalpy of combustion of

H_{2} (g)

at 298 K to give

H_{2} O (g)

- 249 k J m o l^{- 1}

and bond enthalpies of H - H and O = O are

433 k J m o l^{- 1}

and

492 k J m o l^{- 1},

respectively. The bond enthalpy of O - H is

$464 k J m o l^{- 1}$
$928 k J m o l^{- 1}$
$232 k J m o l^{- 1}$
$- 232 k J m o l^{- 1}$

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Q. When

1.0 g

of oxalic acid

(H_{2} C_{2} O_{4})

is burned in a bomb calorimeter whose heat capacity is

8.75 k J / K

, the temperature increases by

0.312 K

. The enthalpy of combustion of oxalic acid at

27^{o} C

is:

$- 300.7 k J / m o l$
$- 280.452 k J / m o l$
$- 241.947 k J / m o l$
None of these

View Solution

Q. The standard enthalpy of combustion at

25^{o} C

of hydrogen, cyclohexene (

C_{6} H_{10}

) and cyclohexane (

C_{6} H_{12}

) are

- 241, - 3800 a n d - 3920 k J m o l^{- 1}

respectively. Calculate the heat of hydrogenation of cyclohexene ( in

k J m o l^{- 1}

)

$- 121$
$+ 121$
$+ 221$
$- 221$

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Q. The heat of combustion of carbon to

C O_{2}

is -393.5 kJ/mol. The heat released upon formation of 35.2g of

C O_{2}

from carbon and oxygen gas is

+315 kJ
-630 kJ
-3.15 kJ
-315 kJ

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Q. The heat of combustion of benzene in a bomb calorimeter (i.e., constant volume) was found to be

3263.9 k J m o l^{- 1}

25^{o} C

. Calculate the heat of combustion of benzene at constant pressure.

$- 4767.6 k J m o l^{- 1}$
$3667.6 k J m o l^{- 1}$
$- 3267.6 k J m o l^{- 1}$
$2767.6 k J m o l^{- 1}$

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Q. The combustion of benzene

(l)

gives

C O_{2} (g)

and

H_{2} O (l)

. Given that the heat of combustion of benzene at constant volume is —3263.9

k J m o l^{- 1}

25^{\circ} C

. The heat of combustion

(i n k J m o l^{- 1})

of benzene at constant pressure will be:

(R = 8.314 J K^{- 1} m o l^{- 1})

-3267.6
4152.6
-452.46
3260

View Solution

The heats of combustion of carbon and carbon monoxide are $- 283.5 a n d - 283.5 k J m o l^{- 1}$ respectively. The heat of formation (in kJ) of carbon monoxide per mole is

676.5
– 676.5
– 110.5
110.5

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Q. The enthalpy change for the reaction,

C_{2} H_{4} (g) + 3 O_{2} (g) ⟶ 2 C O_{2} (g) + 2 H_{2} O (g)

is called:

Enthalpy of formation
Enthalpy of combustion
Enthalpy of vaporization
Enthalpy of sublimation

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Q. The standard enthalpy of formation of octane

(C_{8} H_{18})

- 250 k J / m o l

. Calculate the enthalpy of combustion of

C_{8} H_{18}

.
Given : enthalpy of formation of

C O_{2} (g)

and

H_{2} O (l)

are

- 394 k J / m o l

and

- 286 k J / m o l

respectively:

$- 5200 k J / m o l$
$- 5726 k J / m o l$
$- 5476 k J / m o l$
$- 5310 k J / m o l$

View Solution

Q. When 5 litres of a gas mixture of methane and propane is perfectly combusted at

0^{\circ} C

and 1 atmosphere, 16 litres of oxygen at the same temperature and pressure is consumed. The amount of heat released from this combustion in

k J (Δ H_{c o m b .} (C H_{4}) = 890 k J m o l^{- 1}, Δ H_{c o m b .} (C_{3} H_{8}) = 2220 k J m o l^{- 1})

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Q. The standard heat of combustion of solid boron is equal to

$Δ H_{f}^{0} (B_{2} O_{3})$
$\frac{1}{2} Δ H_{f}^{0} (B_{2} O_{3})$
$2 Δ H_{f}^{0} (B_{2} O_{3})$
$- \frac{1}{2} Δ H_{f}^{0} (B_{2} O_{3})$

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Q. When a certain amount of ethylene was combusted,

6226 kJ

heat was evolved. If heat of combustion of

1

mole of ethylene is

1411 kJ

, the volume of

O_{2}

(at NTP) that entered into the reaction is:

$296.5 mL$
$296.5 litres$
$6226 \times 22.4 litres$
$22.4 litres$

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Q. Which of the following is not an endothermic process

Combustion of methane
Decomposition of water
Dehydrogenation of ethane to ethylene
Conversion of graphite to diamond

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Q. The value of

{log}_{10} K

for a reaction

A ⇌ B

is:

Given : △_{r} H_{298 K}^{\circ} = - 54.07 k J m o l^{- 1}, △_{r} S_{298 K}^{\circ} = 10 J K^{- 1} m o l^{- 1}

and

R = 8.314 J K^{- 1} m o l^{- 1}

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Q. When 5 litres of a gas mixture of methane and propane is perfectly combusted at

0^{\circ} C

and 1 atmosphere, 16 litres of oxygen at the same temperature and pressure is consumed. The amount of heat released from this combustion in

k J (Δ H_{c o m b .} (C H_{4}) = 890 k J m o l^{- 1}, Δ H_{c o m b .} (C_{3} H_{8}) = 2220 k J m o l^{- 1})

View Solution

Q. The combustion of hydrogen-oxygen mixture is used to produce very high temperatures

(= 2500^{\circ} C)

needed for certain types of welding operations.

H_{2} (g) + \frac{1}{2} O_{2} (g) \to H_{2} O (g)

;

Δ H = - 230.9 kJ

Quantity of heat, (in kJ) evolved when a

200 g

mixture containing equal parts of

H_{2}

and

O_{2}

mass is burned, is

$- 2.72 \times 10^{3} kJ$
$- 1.36 \times 10^{3} kJ$
$- 1.44 \times 10^{3} kJ$
$- 4.3524 \times 10^{4} kJ$

View Solution

Q. The heat of combustion of benzene in a bomb calorimeter (i.e., constant volume) was found to be

3263.9 k J m o l^{- 1}

25^{o} C

. Calculate the heat of combustion of benzene at constant pressure.

$- 4767.6 k J m o l^{- 1}$
$3667.6 k J m o l^{- 1}$
$- 3267.6 k J m o l^{- 1}$
$2767.6 k J m o l^{- 1}$

View Solution

Q. The total entropy change

(△ S_{t o t a l})

for the system and the surrounding of a spontaneous process is given by:

$△ S_{t o t a l} = △ S_{s y s t e m} + △ S_{s u r r} > 0$
$△ S_{t o t a l} = △ S_{s y s t e m} - △ S_{s u r r} > 0$
$△ S_{s y s t e m} = △ S_{t o t a l} + △ S_{s u r r} > 0$
$△ S_{s u r r} = △ S_{t o t a l} - △ S_{s y s t e m} < 0$

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Q. The heat of formation of

C O

and

C O_{2}

are

- 26.4

kcal and

- 94

kcal respectively. The heat of combustion of carbon monoxide will be:

$+ 26.4$ kcal
$- 67.6$ kcal
$- 120.4$ kcal
$+ 52.8$ kcal

View Solution