Heat of React...

Heat of Reaction

Trending Questions

Q. The enthalpy of solution of

B a C l_{2} (s)

and

B a C l_{2} .2 H_{2} O (s)

are – 20.6 and 8.8 kJ

m o l^{- 1}

respectively, the enthalpy change for the hydration of

B a C l_{2} (s)

is:

29.4 kJ
– 11.8 kJ
– 29.4 kJ
+ 11.8 kJ

View Solution

In an endothermic reaction, the value of ΔH is always________

View Solution

Is negative delta H exothermic?

View Solution

Q. Calculate the enthalpy change

(△ H)

of the following reaction

2 C_{2} H_{2} (g) + 5 O_{2} (g) \to 4 C O_{2} (g) + 2 H_{2} O (g)

given average bond enthalpies of various bonds, i.e.,

C - H, C \equiv C, O = O, C = O, O - H

as 414, 814 499, 724 and 640

k J m o l^{- 1}

respectively.

$- 2600 k J m o l^{- 1}$
$+ 2573 k J m o l^{- 1}$
$- 2573 k J m o l^{- 1}$
$+ 2600 k J m o l^{- 1}$

View Solution

Q. Calculate resonance energy of

N_{2} O

from the following data
Hence,

△ H^{\circ} (N_{2} O) = 82 k J m o l^{- 1}

Assume structure

N^{Θ} = N^{⨁} = O

BE of

(N \equiv N) b o n d = 950 k J m o l^{- 1}

(N = N) b o n d = 420 k J

mol

^{- 1}

O = O) b o n d = 500 k J m o l^{- 1}

(O = N) b o n d = 610 k J m o l^{- 1}

$- 170 k J m o l^{- 1}$
$- 356 k J m o l^{- 1}$
$- 88 k J m o l^{- 1}$
$- 190 k J m o l^{- 1}$

View Solution

Is $∆ H$ positive or negative?

View Solution

Q. Carbon tetrachloride

(C C l_{4})

is mixed in

390 g

of benzene to make a solution for supporting an organic chemical reaction in which mole fraction of benzene is

0.91

. Find the molality of the

C C l_{4}

solution.

$4.44 m$
$4.25 m$
$2.67 m$
$1.26 m$

View Solution

Q. Calculate

△ H_{r}^{o}

for the reaction

C H_{2} C l_{2} (g) \to C (g) + 2 H (g) + 2 C l (g) .

The average bond enthalpies of C - H and C - Cl bonds are

414 k J m o l^{- 1}

and

330 k J m o l^{- 1} .

$1488 k J m o l^{- 1}$
$1468 k J m o l^{- 1}$
$1478 k J m o l^{- 1}$
$1498 k J m o l^{- 1}$

View Solution

Q. Given,

H_{2} S_{(g)} \to H S (g) + H (g); △ H_{r x n} = 379.6 k J m o l^{- 1}

H_{2} (g) + S (s) \to H_{2} S (g);

△ H_{f}^{\circ} H_{2} S = - 21.1

k J m o l^{- 1}

H_{2 (g)} \to 2 H_{(g)}

;

Δ H = 438 k J m o l^{- 1}

Δ H_{s u b l i m a t i o n}

of S =

280 k J m o l^{- 1}

Thus,

△ H_{f}^{\circ} H S

$138.5 k J m o l^{- 1}$
$- 138.5 k J m o l^{- 1}$
$- 277.0 k J m o l^{- 1}$
$+ 139.5 k J m o l^{- 1}$

View Solution

Which of the following properties is not a function of state?

concentration
internal energy
enthalpy
entropy

View Solution

Q. Given:

⎡ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ \begin{matrix} H_{2} (g) + \frac{1}{2} O_{2} (g) = H_{2} O (g); Δ H = - 241.8 k J C_{2} H_{2} (g) + \frac{5}{2} O_{2} (g) = 2 C O_{2} (g) + H_{2} O (g); Δ H = - 1300 k J \end{matrix} ⎤ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦

Equal volumes of

C_{2} H_{2}

and

H_{2}

are combusted under identical conditions. The ratio of heats evolved in the two cases is

5.37/1
1/5.37
1/1
none of these

View Solution

Q. Given that:

C (g r a p h i t e) + O_{2} (g) \to C O_{2} (g), Δ H = x k J m o l^{- 1}

C (g r a p h i t e) + \frac{1}{2} O_{2} (g) \to C O (g), Δ H = y k J m o l^{- 1}

C O (g) + \frac{1}{2} O_{2} (g) \to C O_{2} (g), Δ H = z k J m o l^{- 1}

Based on the given thermochemical equations, find out which one of the following algebric relationships is correct?

$z = x + 2 y$
$z = x - y$
$z = x + y$
$2 z = x - y$

View Solution

Q. A solution of 200 mL of 1 M KOH is added to 200 mL of 1 M HCl and the mixture after attaining reaction equilibrium shows a rise in temperature by

△ T_{1} .

The experiment is repeated by using 50 mL of 1 M KOH and 50 mL 1 M HCl which at equilibrium shows a rise in temperature by

△ T_{2} .

Thus:

$△ T_{1} = △ T_{2}$
$△ T_{1} = 4 \times △ T_{2}$
$△ T_{1} = 2 \times △ T_{2}$
$△ T_{1} > △ T_{2}$

View Solution

Q. Which equation do not represent enthalpy change of reaction which correspond to the standard enthalpy change of atomisation of chlorine?

$\frac{1}{2} C l_{2} (g) \to C l (g)$
$\frac{1}{2} C l_{2} (l) \to C l (g)$
$C l_{2} (g) \to 2 C l (g)$
$C l_{2} (l) \to 2 C l (g)$

View Solution

Q. The following sequence of reaction occurs in commercial production of aqueous nitric acid.

4 N H_{3} (g) + 5 O_{2} (g) \to 4 N O (g) + 6 H_{2} O (l) Δ H = - 904 k J . . . (1)

2 N O (g) + O_{2} (g) \to 2 N O_{2} (g) Δ H = - 112 k J . . . (2)

3 N O_{2} (g) + H_{2} O (l) \to 2 H N O_{3} (a q) + N O (g) Δ H = - 140 k J . . . (3)

Determine the magnitude of total heat

(i n kJ/mole)

liberated at constant pressure for the production of exactly 1 mole of aqueous nitric acid by this process

View Solution

Q. Calculate the heat evolved when 496 g of white phosphorus

P_{4}

burns in air according to equation

P_{4} (s) + 5 O_{2} (g) \to P_{4} O_{10} (s)

Δ H = - 3013 k J / m o l

$60226 k J$
$12052 k J$
$1252 k J$
$3052 k J$

View Solution

Q. The average Xe - F bond energy is 34 kcal/mol, first I.E. of Xe is 279 kcal/mol, electron affinity of F is 85 kcal/mol and bond dissociation energy of

F_{2}

is 38 kcal/mol. Then, the enthalpy change for the reaction

X e F_{4} \to X e^{+} + F^{-} + F_{2} + F

will be

367 kcal/mol
425 kcal/mol
292 kcal/mol
392 kcal/mol

View Solution

Q. Calculate the heat evolved when 248 g of white phosphorus

P_{4}

burns in air according to equation

P_{4} (s) + 5 O_{2} (g) \to P_{4} O_{10} (s)

Δ H = - 3013 k J / m o l e

$4266$ kJ
$9026$ kJ
$3013$ kJ
$6026$ kJ

View Solution

Q. The polymerisation of propene to linear polypropene is represented by the reaction:

where n has a large integral value. The average enthalpies of bond dissociation for

(C = C)

and

(C - C)

at 298 K are +590 and

+ 331 {kJmol}^{- 1}

, respectively. The enthalpy of polymerisation is

- 360 {kJmol}^{- 1}

. Find the value of n.

View Solution

Q. Calculate

△ H_{r}^{o}

for the reaction

C H_{2} C l_{2} (g) \to C (g) + 2 H (g) + 2 C l (g) .

The average bond enthalpies of C - H and C - Cl bonds are

414 k J m o l^{- 1}

and

330 k J m o l^{- 1} .

$1488 k J m o l^{- 1}$
$1468 k J m o l^{- 1}$
$1478 k J m o l^{- 1}$
$1498 k J m o l^{- 1}$

View Solution

Q. What is value of

△ U

(heat change at constant volume) for reversible isothermal evaporation of 90 g water at

100^{o} C .

Assuming water vapour behaves as an ideal gas and

(△ H_{v a p})_{w a t e r} = 540 c a l g^{- 1}

$9 \times 10^{3} k c a l$
$6 \times 10^{3} k c a l$
$4.49 \times 10^{3} c a l$
none of these

View Solution

Q. Given,

C_{(g r a p h i t e s)} + O_{2} (g) \to C O_{2} (g)

Δ_{r} H^{\circ} = - 393.5 k J m o l^{- 1}

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

Δ_{r} H^{\circ} = - 285.8 k J m o l^{- 2}

C O_{2} (g + 2 H_{2} O (l) \to C H_{4} (g) + 2 O_{2} (g)

Δ_{r} H^{\circ} = + 890.3 k J m o l^{- 1}

Based on the above thermochemical equations, the value of

Δ_{r} H^{\circ}

at 298K for the reaction,

C_{(g r a p h i t e)} + 2 H_{2} (g) \to C H_{4} (g)

will be

$+ 78.8 k J m o l^{(- 1)}$
$+ 144.0 k J m o l^{(- 1)}$
$- 74.8 k J m o l^{(- 1)}$
$- 144.0 k J m o l^{(- 1)}$

View Solution

Q. The heats of combustion of rhombic and monoclinic sulphur are 70960 and 71030 cal/mol respectively. Calculate the heat of conversion of rhombic to monoclinic sulphur

70960 cal
71030 cal
- 70 cal
70 cal

View Solution

Q. One mole of soda ash dissolves in water with evolution of 25 kJ of heat. Dissociation of 1 mol of the hydrate crystals in water resulted in the absorption of 67 kJ of heat. The heat released due to hydration of soda ash is

$- 92 k J$
$+ 42 k J$
$- 42 k J$
$- 102 k J$

View Solution

Consider the following data:

$Δ f H^{0} (N_{2} H_{4}, l) = 50 k J / m o l$

$Δ f H^{0} (N H_{3}, g) = - 46 k J / m o l$

$B . E . (N - H) = 393 k J / m o l$ and $B . E . (H - H) = 436 k J / m o l$ , also $Δ_{v a p} H (N_{2} H_{4}, l) = 18 k J / m o l$

The N- N bond energy in $N_{2} H_{4}$ is

226 kJ/mol
154 kJ/mol
190 kJ/mol
45.45 kJ/mol

View Solution

Q. The increase in internal energy of 1 kg of water at

100^{0} C

when it is converted into steam at the same temperture and at 1 atm (100 kPa) will be:
(The density of water and steam are

1000 k g / m^{3}

and

0.6 k g / m^{3}

respectively. The latent heat of vapourisation of water is 2.25

10^{6}

J/kg.)

$2.08 \times 10^{6} J$
$4 \times 10^{7} J$
$3.27 \times 10^{8} J$
$5 \times 10^{9} J$

View Solution

Q. If heat of dissociation of

C H C l_{2} C O O H

is 0.7 kcal/mol, then

△ H

for the reaction:

C H C l_{2} C O O H + K O H \to C H C l_{2} C O O K + H_{2} O

- 13 kcal
+13 kcal
-14.4 kcal
-13.7 kcal

View Solution

Q. The specific heats of iodine vapour and solid are

0.031

and

0.055 c a l K^{- 1} g^{- 1}

respectively. If heat of sublimation of iodine is

24 c a l g^{- 1}

200^{o} C

, find its value at

250^{\circ} C

$5.7 c a l g^{- 1}$
$11.4 c a l g^{- 1}$
$22.8 c a l g^{- 1}$
$45.6 c a l g^{- 1}$

View Solution

Q. For the combustion of 1 mol of liquid benzene at

25^{o} C

, the heat of reaction at constant pressure is given by,

C_{6} H_{6} (l) + \frac{15}{2} O_{2} (g) \to 6 C O_{2} (g) + 3 H_{2} O (l)

;

Δ H = - 780980 c a l

.
What would be the heat of reaction at constant volume?

$750985 c a l$
$- 700980 c a l$
$- 880090 c a l$
$- 780006 c a l$

View Solution

Q. Methane is a commercial source of

H_{2}

through the reaction
(I)

C H_{4} (g) + \frac{1}{2} O_{2} (g) \to C O (g) + 2 H_{2} (g)

Based on the following thermochemical equations (II to IV)
(II)

C H_{4} (g) + 2 O_{2} (g) \to C O_{2} (g) + 2 H_{2} O (g); △ H = - 800 k J

(III)

C H_{4} (g) + C O_{2} (g) \to 2 C O (g) + 2 H_{2} (g); △ H = + 235 k J

(IV)

C H_{4} (g) + H_{2} O (g) \to C O (g) + 3 H_{2} (g); △ H = + 204 k J

△ H

of equation (I) is

-35.75 kJ
- 39.25 kJ
- 25.75 kJ
+ 25.75 kJ

View Solution