Alpha Question Bank for Medical: Chemistry>Chapter 4 - Thermodynamics>Exercise 5>Q 34

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$S_{1} :$ Molar heat at a constant pressure $=$ Molar heat at a constant volume $+ PΔV$
$S_{2} : {ΔH}_{sub} = {ΔH}_{fusion} + {ΔH}_{vap}$
$S_{3} :$ Pressure is an intensive property.
$S_{4} :$ For reaction $2 A (g) + B (g) ⟶ (g) ΔH = - x kJ$ , then for reaction
$\frac{3}{2} C (g) - A (g) + \frac{B}{2} (g) ΔH = \frac{X}{2} kJ$

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Important Questions on Thermodynamics

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Alpha Question Bank for Medical: Chemistry>Chapter 4 - Thermodynamics>Exercise 5>Q 35

Stearic acid

[{CH}_{3} {({CH}_{2})}_{16} {CO}_{2} H)

is a fatty acid, the part of fat that stores most of the energy.

1.0 g

of stearic acid was burned in a bomb calorimeter. The bomb had a heat capacity of

652 J / {}^{\circ}C .

If the temperature of

500 g

water

(c = 4.18 J / g {}^{\circ}C)

increase from

25.0

to

39.3 ° C,

how much heat was released when the stearic acid was burned?

[Given C_{p} (H_{2} O) = 4.18 J / 8 ° C]

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Alpha Question Bank for Medical: Chemistry>Chapter 4 - Thermodynamics>Exercise 5>Q 36

(i)

Cis-2-butene \to trans-2-butene, Δ H_{1}

(ii)

Cis-2-butene \to 1-butene, Δ H_{2}

(iii) Trans-2-butene is more stable than cis-2-butene

(iv) Enthalpy of combustion of 1-butene,

Δ H = - 649.8 kcal/mol

(v)

9 Δ H_{1} + 5 Δ H_{2} = 0

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

Δ H = - 647.0 kcal/mol

The value of

Δ H_{1}

and

Δ H_{2}

in kcal/mol are

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Alpha Question Bank for Medical: Chemistry>Chapter 4 - Thermodynamics>Exercise 5>Q 37

Use the following data to calculate the enthalpy of formation of

{As}_{2} O_{3}

:
(i)

{As}_{2} O_{3} (s) + [(3 H_{2} O + aq)] ⟶ 2 H_{3} {AsO}_{3} (aq)

ΔH = + 7550

cal

(ii)

As (s) + \frac{3}{2} {Cl}_{2} (g) ⟶ {AsCl}_{3} (ℓ)

ΔH = - 71390

cal

(iii)

{AsCl}_{3} (ℓ) + (3 H_{2} O + aq) ⟶ H_{3} {AsO}_{3} (aq) + 3 HCl (aq); ΔH = - 17580 cal

(iv)

HCl (g) + aq ⟶ HCl (aq)

ΔH = - 17315 cal

(v)

\frac{1}{2} H_{2} (g) + \frac{1}{2} {Cl}_{2} (g) ⟶ HCl (g)

ΔH = - 22000 cal

(vi)

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

ΔH = - 68360

cal

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Alpha Question Bank for Medical: Chemistry>Chapter 4 - Thermodynamics>Exercise 5>Q 38

From the following data calculate the enthalpy change for the sublimation of ice at

223 K

[mean heat capacity of ice

= 2 {JK}^{- 1} {gm}^{- 1},

mean heat capacity of

H_{2} O (ℓ) = 4.2 {JK}^{- 1} {gm}^{- 1},

mean heat capacity of

H_{2} O (v) = 1.85 {JK}^{- 1} {gm}^{- 1},

enthalpy of fusion of ice at

0 ° C = 334 {Jgm}^{- 1},

enthalpy of evaporation of water
at

[100 ° = 2255 J {gm}^{- 1}]