EASY

Earn 100

Define the enthalpy of fusion.

Important Questions on Energetics (Thermochemistry)

MEDIUM

Chemistry>Physical Chemistry>Energetics (Thermochemistry)>Enthalpies for Different Types of Reactions

Enthalpy of sublimation of iodine is

24 c a l g^{- 1}

200 ° C

. If specific heat of

I_{2}

(s) and

I_{2}

(vap) are

0.055

and

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

respectively, then enthalpy of sublimation of iodine at

250 ° C

c a l g^{- 1}

is:

HARD

Chemistry>Physical Chemistry>Energetics (Thermochemistry)>Enthalpies for Different Types of Reactions

An athlete is given $100 g$ of glucose $(C_{6} H_{12} O_{6})$ for energy. This is equivalent to $1800 kJ$ of energy. The $50 %$ of this energy gained is utilized by the athlete for sports activities at the event. In order to avoid storage of energy, the weight of extra water he would need to perspire is $_____g$ (Nearest integer) Assume that there is no other way of consuming stored energy.

Given : The enthalpy of evaporation of water is $45 kJ {mol}^{- 1}$

Molar mass of $C, H & O$ are $12.1$ and $16 g {mol}^{- 1}$ .

MEDIUM

Chemistry>Physical Chemistry>Energetics (Thermochemistry)>Enthalpies for Different Types of Reactions

Calculate the enthalpy change. For the change $8 S (g) \to S_{8} (g)$ , given that

$H_{2} S_{2} (g) \to 2 H (g) + 2 S (g), ΔH = 239 .0 k c a l m o l^{- 1}$

$H_{2} S (g) \to 2 H (g) + S (g), ΔH = 175 .0 k c a l m o l^{- 1}$

EASY

Chemistry>Physical Chemistry>Energetics (Thermochemistry)>Enthalpies for Different Types of Reactions

298 K

, the enthalpy of fusion of a solid

(X)

2.8 kJ {mol}^{- 1}

and the enthalpy of vaporisation of the liquid

(X)

98.2 kJ {mol}^{- 1}

. The enthalpy of sublimation of the substance

(X)

kJ {mol}^{- 1}

is ______. (in nearest integer)

EASY

Chemistry>Physical Chemistry>Energetics (Thermochemistry)>Enthalpies for Different Types of Reactions

The enthalpy change on freezing of

1 mol

of water at

5 ° C

to ice at

- 5 ° C

is:

(Given

Δ_{fus} H = 6 kJ {mol}^{- 1}

0 ° C,

C_{p} (H_{2} O, l) = 75 .3 J {mol}^{- 1} K^{- 1}

C_{p} (H_{2} O, s) = 36 .8 J {mol}^{- 1} K^{- 1}

)

HARD

Chemistry>Physical Chemistry>Energetics (Thermochemistry)>Enthalpies for Different Types of Reactions

Enthalpy of fusion and enthalpy of vaporization for water respectively are

6.01 kJ {mol}^{- 1}

and

45.07 kJ {mol}^{- 1}

0 ° C

what is enthalpy of sublimation at

0 ° C

EASY

Chemistry>Physical Chemistry>Energetics (Thermochemistry)>Enthalpies for Different Types of Reactions

Select correct statement?

HARD

Chemistry>Physical Chemistry>Energetics (Thermochemistry)>Enthalpies for Different Types of Reactions

The enthalpy of sublimation of aluminium is

330 kJ / mol .

It’s first, second and third ionization enthalpies are

580, 1820 and 2740 kJ

respectively. How much heat has to be supplied (in

kJ

) to convert

13.5 gram

of aluminium into

{Al}^{3 +}

ions and electrons at

298 K

HARD

Chemistry>Physical Chemistry>Energetics (Thermochemistry)>Enthalpies for Different Types of Reactions

In solid $\mathrm{NH}_{3},$ each $\mathrm{NH}_{3}$ molecule has six other $\mathrm{NH}_{3}$ molecules as nearest neighbours. $\Delta H$ of sublimation of $\mathrm{NH}_{3}$ at the melting point is $30.8 \mathrm{kJ} / \mathrm{mol}$ and the estimated $\Delta H$ of sublimation in absence of $\mathrm{H}$ -bonding is $14.3 \mathrm{kJ} / \mathrm{mol} .$ The strength of H-bond in $\mathrm{NH}_{3}$ ion $\mathrm{kJ} / \mathrm{mol}$ is :

EASY

Chemistry>Physical Chemistry>Energetics (Thermochemistry)>Enthalpies for Different Types of Reactions

The correct order of enthalpy of vaporization of noble gases is

EASY

Chemistry>Physical Chemistry>Energetics (Thermochemistry)>Enthalpies for Different Types of Reactions

25^{o} C

the heat of formation of

H_{2} O (l)

- 285.9 K J m o l e^{- 1}

and that for

H_{2} O (g)

- 242.8 K J m o l e^{- 1}

. The heat of vaporization of water at the same temperature is

EASY

Chemistry>Physical Chemistry>Energetics (Thermochemistry)>Enthalpies for Different Types of Reactions

Considering that water vapour is one of the ideal gases, the internal energy change

(ΔU)

1 bar

pressure and

1000 C

, when

1 mol

of water is vapourised , (molar enthalpy of vapourisation of water at

373 K

and

1 bar = 41 kJ {mol}^{- 1}

and

R = 8.3 J {mol}^{- 1} K^{- 1}

) will be:

MEDIUM

Chemistry>Physical Chemistry>Energetics (Thermochemistry)>Enthalpies for Different Types of Reactions

The enthalpy of reaction

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

and that of

H_{2} (g) + \frac{1}{2} O_{2} (g) \to H_{2} O (l) i s ∆ H_{2}

.

Then

MEDIUM

Chemistry>Physical Chemistry>Energetics (Thermochemistry)>Enthalpies for Different Types of Reactions

Standard enthalpy of vaporisation

Δ_{vap} H^{\circ}

for water at 100oC is 40.66 kJ mol^-1. The internal energy of vaporisation of water at 100^oC (in kJ mol^-1) is

EASY

Chemistry>Physical Chemistry>Energetics (Thermochemistry)>Enthalpies for Different Types of Reactions

Of these quantities, the one that we except to be largest

MEDIUM

Chemistry>Physical Chemistry>Energetics (Thermochemistry)>Enthalpies for Different Types of Reactions

Represent the union of two sets by Venn diagram for each of the following.

$X = {x | x$ is a prime number between $80$ and $100}$

$Y = {y | y$ is an odd number between $90$ and $100}$

MEDIUM

Chemistry>Physical Chemistry>Energetics (Thermochemistry)>Enthalpies for Different Types of Reactions

What is the value of change in internal energy at 1 atm in the process?

H_{2} O (l, 323 K) \to H_{2} O (g, 423 K)

Given:

C_{v, m} (H_{2} O, l) = 75.0 J K^{- 1} m o l^{- 1}

;

∆ H_{v a p}

373 K = 40.7 K J / m o l

C_{p, m} (H_{2} O, g) = 33.314 J K^{- 1} m o l^{- 1}

MEDIUM

Chemistry>Physical Chemistry>Energetics (Thermochemistry)>Enthalpies for Different Types of Reactions

Enthalpy change when

1 g

water is frozen at

0 ℃

(∆ H_{f u s} = 1.4354 k c a l m o l^{- 1})

EASY

Chemistry>Physical Chemistry>Energetics (Thermochemistry)>Enthalpies for Different Types of Reactions

Enthalpy of fusion of a liquid is

1.435 kcal {mol}^{- 1}

and molar entropy change is

5.26 cal {mol}^{- 1} K^{- 1}

. Hence, the melting point of the liquid is

EASY

Chemistry>Physical Chemistry>Energetics (Thermochemistry)>Enthalpies for Different Types of Reactions

The sublimation energy of

I_{2} (s)

57.3 KJ / mol

and the enthalpy of fusion is

15.5 KJ / mol

. What is the enthalpy of vaporisation of

I_{2}

Define the enthalpy of fusion.

Important Questions on Energetics (Thermochemistry)

Learn and Prepare for any exam you want !