# SCERT Maharashtra Question Bank solutions for 12th Standard HSC Chemistry Maharashtra State Board 2021 chapter 4 - Chemical Thermodynamics [Latest edition]

## Chapter 4: Chemical Thermodynamics

Multiple choice questions

### SCERT Maharashtra Question Bank solutions for 12th Standard HSC Chemistry Maharashtra State Board 2021 Chapter 4 Chemical Thermodynamics Multiple choice questions

#### 1 Mark

Multiple choice questions | Q 1

An intensive property amongst the following is ______.

• Mass

• Volume

• Number of moles

• Temperature

Multiple choice questions | Q 2

The value of 1dm3 bar is ______.

• 10 J

• 102 J

• 103 J

• 10-2 J

Multiple choice questions | Q 3

The work done in the dm3 bar when 200 mL of ethylene gas and 150 mL of HCl gas were allowed to react at 1 bar pressure is ______.

• 0.10

• 0.15

• 0.20

• 0.2

Multiple choice questions | Q 4

The work done in vacuum when 300 m mole of an ideal gas expands until its volume is increased by 2.3 dm3 at 1 bar pressure is ______ mole.

• Zero

• One

• Two

• Three

Multiple choice questions | Q 5

For an Isothermal process

• W = - Q

• ∆U = W

• ∆U = Q + W

• ∆U = Q

Multiple choice questions | Q 6

For an Isochoric process

• ∆U = 0

• ∆V = 0

• ∆P = 0

• Q = 0

Multiple choice questions | Q 7

The change in internal energy in a reaction when 2kJ of heat is released by the system and 6 kJ of work is done on the system will be ______.

• +4 kJ

• 4kJ

• +3 kJ

• – 8 kJ

### SCERT Maharashtra Question Bank solutions for 12th Standard HSC Chemistry Maharashtra State Board 2021 Chapter 4 Chemical Thermodynamics Very short answer questions

#### 1 Mark

Very short answer questions | Q 1

Write the expression to calculate maximum work done when 1 mole of an ideal gas expands isothermally and reversibly from V1 to V2.

Very short answer questions | Q 2

Write the mathematical relation between ΔH and ΔU during the formation of one mole of CO2 under standard conditions.

Very short answer questions | Q 3

The standard enthalpy of formation of water is - 286 kJ mol-1. Calculate the enthalpy change for the formation of 0.018 kg of water.

Very short answer questions | Q 4

Write the mathematical expression of the First Law of Thermodynamics for the Isobaric process

Very short answer questions | Q 5

What is the sign convention when work is done on the system by the surrounding?

Very short answer questions | Q 6

Write the expression showing the relation between enthalpy change and internal energy change for gaseous phase reaction.

Very short answer questions | Q 7

Calculate enthalpy of formation of HCl if bond enthalpies of H2, Cl2 and HCl are 434 kJ mol-1, 242 kJ mol–1 and 431 kJ mol–1 respectively.

### SCERT Maharashtra Question Bank solutions for 12th Standard HSC Chemistry Maharashtra State Board 2021 Chapter 4 Chemical Thermodynamics Short answer questions (Type- I)

#### 2 Marks

Short answer questions (Type- I) | Q 1.1

Define the Standard enthalpy of combustion.

Short answer questions (Type- I) | Q 1.2

Define the Enthalpy of sublimation.

Short answer questions (Type- I) | Q 2

State and explain Hess’s law of constant heat summation.

Short answer questions (Type- I) | Q 3

Write the features of reversible processes.

Short answer questions (Type- I) | Q 4

Derive an expression for pressure-volume work.

Short answer questions (Type- I) | Q 5

The enthalpy change of the following reaction

$\ce{CH_{4(g)} + Cl_{2(g)} -> CH3Cl_{(g)} + HCl_{(g)}}$

ΔH° = –104 kJ. Calculate C – Cl bond enthalpy.

The bond enthalpies are

 Bond C − H Cl − Cl H − Cl ∆H°/kJ mol−1 414 243 431
Short answer questions (Type- I) | Q 6

Calculate the standard enthalpy of combustion of CH4(g) if ΔfH°(CH4) = – 74.8 kJ mol–1, ΔfH°(CO2) = – 393.5 kJ mol–1 and ΔfH°(H2O) = – 285.8 kJ mol–1.

### SCERT Maharashtra Question Bank solutions for 12th Standard HSC Chemistry Maharashtra State Board 2021 Chapter 4 Chemical Thermodynamics Short answer questions (Type- II)

#### 3 Marks

Short answer questions (Type- II) | Q 1

Define an isolated system.

Short answer questions (Type- II) | Q 1

Three moles of an ideal gas are expanded isothermally from 15 dm3 to 20 dm3 at a constant external pressure of 1.2 bar, calculate the amount of work in Joules.

Short answer questions (Type- II) | Q 2

Answer the following in one or two sentences.

What is enthalpy of fusion?

Short answer questions (Type- II) | Q 2

Derive the expression for the maximum work.

Short answer questions (Type- II) | Q 3

Derive the expression for work done in chemical reaction. Write the relationship between ∆H and ∆U for an isochoric process.

Short answer questions (Type- II) | Q 4

Define standard enthalpy of formation.

Short answer questions (Type- II) | Q 5

0.022 kg of CO2 is compressed isothermally and reversibly at 298 K from an initial pressure of 100 kPa when the work obtained is 1200 J, calculate the final pressure.

Short answer questions (Type- II) | Q 6.1

Define the Enthalpy of vaporization.

Short answer questions (Type- II) | Q 6.2

Define the Standard enthalpy of combustion.

Short answer questions (Type- II) | Q 6.3

Why work done in vacuum is zero?

### SCERT Maharashtra Question Bank solutions for 12th Standard HSC Chemistry Maharashtra State Board 2021 Chapter 4 Chemical Thermodynamics Long answer questions, Long Answer Questions

#### 4 Marks

Long answer questions | Q 1.1

Define the Enthalpy of atomization.

Long answer questions | Q 1.1

Define the Extensive properties.

Long answer questions | Q 1.2

Calculate the standard enthalpy of formation of liquid methanol from the following data:

1. $\ce{CH3OH_{(l)} + \frac{3}{2} O_{2(g)} -> CO_{2(g)} + 2H2O_{(l)}}$     ∆H° = – 726 kJ mol–1
2. $\ce{C_{(Graphite)} + O_{2(g)} -> CO_{2(g)}}$          ∆cH° = – 393 kJ mol–1
3. $\ce{H_{2(g)} + \frac{1}{2} O_{2(g)} -> H2O_{(l)}}$          ∆fH° = – 286 kJ mol–1
Long answer questions | Q 2.1

Define the Bond enthalpy.

Long answer questions | Q 2.2

Define the Enthalpy of ionisation.

Long answer questions | Q 2.3

Calculate the standard enthalpy of the reaction.

$\ce{2Fe_{(s)} + \frac{3}{2} O_{2(g)} -> Fe2O_{3(s)}}$

Given:

 1 $\ce{2Al_{(s)} + Fe2O_{3(s)} -> 2Fe_{(s)} + Al_2O_{3(s)}}$, ∆rH° = –847.6 kJ 2 $\ce{2Al_{(s)} + \frac{3}{2} O_{2(g)} -> Al2O_{3(s)}}$, ∆rH° = –1670 kJ
Long answer questions | Q 3.1

How much heat is evolved when 12 g of CO reacts with NO2? The reaction is:

4CO(g)  2NO2(g) → 4CO2(g) + N2(g), ΔrH° = - 1200 kJ

Long answer questions | Q 3.2

Write an application of Hess’s law.

Long answer questions | Q 3.3

Does the following reaction represent a thermochemical equation?

$\ce{CH_{4(g)} + 2O_{2(g)} -> CO_{2(g)} + 2H2O_{(g)}}$, ∆fH° = –900 kJ mol–1

Long answer questions | Q 4.1

Classify the following into intensive and extensive properties.

Pressure, volume, mass, temperature.

Long Answer Questions | Q 4.2

Define state function and write two examples of it.

## SCERT Maharashtra Question Bank solutions for 12th Standard HSC Chemistry Maharashtra State Board 2021 chapter 4 - Chemical Thermodynamics

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Concepts covered in 12th Standard HSC Chemistry Maharashtra State Board 2021 chapter 4 Chemical Thermodynamics are Chemical Thermodynamics, Terms Used in Thermodynamics, Nature of Heat and Work, Expression for Pressure-volume (PV) Work, Concept of Maximum Work, Internal Energy (U), First Law of Thermodynamics, Enthalpy (H), Enthalpies of Physical Transformations, Thermochemistry, Spontaneous (Irreversible) Process.

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