Grade 11 : Chemistry - Thermodynamics (Set 2)

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Grade 11 : Chemistry - Thermodynamics (Set 2)— Questions & Detailed Solutions

A chef boils soup in an open steel pot on a gas burner. Steam escapes continuously into the kitchen while thermal energy is supplied from the flame.
Which type of thermodynamic system does the open pot of soup represent?

(A)

Isolated system

(B)

Open system

(C)

Closed system

(D)

Adiabatic system

View Correct Answer & Detailed Solution

✓ Correct Option: (B)

Explanation:An open system can exchange both matter (steam/water vapor) and energy (heat from burner) with its surroundings.

A gas sample inside a flexible cylinder absorbs 250 J of heat from its environment while expanding against an external piston, doing 100 J of work on the surroundings.
Calculate the change in internal energy ($\Delta U$) of the gas system.

(A)

+150 J

(B)

+350 J

(C)

-150 J

(D)

-350 J

View Correct Answer & Detailed Solution

✓ Correct Option: (A)

Explanation:By the First Law of Thermodynamics, $\Delta U = q + w$. Heat absorbed $q = +250\text{ J}$ and work done by the system $w = -100\text{ J}$. Thus, $\Delta U = 250 - 100 = +150\text{ J}$.

Which of the following physical quantities is classified as a path function rather than a state function?

(A)

Enthalpy ($H$)

(B)

Internal Energy ($U$)

(C)

Entropy ($S$)

(D)

Heat ($q$)

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✓ Correct Option: (D)

Explanation:Heat ($q$) and Work ($w$) depend on the specific path taken between initial and final states, making them path functions. Enthalpy, internal energy, and entropy depend only on the state.

Which of the following thermodynamic properties is an intensive property?

(A)

Total volume

(B)

Total mass

(C)

Temperature

(D)

Heat capacity

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✓ Correct Option: (C)

Explanation:An intensive property does not depend on the quantity of matter present. Temperature is independent of system size, whereas volume, mass, and heat capacity are extensive properties.

A chemical hand warmer releases thermal energy into the surroundings when iron powder oxidizes inside a porous pouch.
What is the correct sign of the enthalpy change ($\Delta H$) for this reaction?

(A)

$\Delta H > 0$

(B)

$\Delta H < 0$

(C)

$\Delta H = 0$

(D)

$\Delta H = \infty$

View Correct Answer & Detailed Solution

✓ Correct Option: (B)

Explanation:Processes that release heat to surroundings are exothermic, which by convention have a negative enthalpy change ($\Delta H < 0$).

A 50 g sample of pure copper (specific heat capacity $c = 0.385\text{ J}/(g\cdot^\circ\text{C})$) is heated, increasing its temperature by $20^\circ\text{C}$.
How much heat energy ($q$) did the copper sample absorb?

(A)

38.5 J

(B)

192.5 J

(C)

385 J

(D)

770 J

View Correct Answer & Detailed Solution

✓ Correct Option: (C)

Explanation:Use $q = m \cdot c \cdot \Delta T$. Substituting: $q = 50g \times 0.385\text{ J}/(g\cdot^\circ\text{C}) \times 20^\circ\text{C} = 385\text{ J}$.

A gas contained in a thermally insulated cylinder undergoes a expansion process such that no heat transfers between system and surroundings.
What is the value of heat transfer ($q$) for this adiabatic process?

(A)

$q > 0$

(B)

$q < 0$

(C)

$q = 0$

(D)

$q = w$

View Correct Answer & Detailed Solution

✓ Correct Option: (C)

Explanation:By definition, an adiabatic process occurs with complete thermal insulation, meaning zero heat transfer ($q = 0$).

A gas expands from an initial volume of 2.0 L to a final volume of 5.0 L against a constant external pressure of 2.0 atm.
Calculate the work done ($w$) by the gas in $\text{L}\cdot\text{atm}$.

(A)

$+6.0\text{ L}\cdot\text{atm}$

(B)

$-6.0\text{ L}\cdot\text{atm}$

(C)

$+10.0\text{ L}\cdot\text{atm}$

(D)

$-10.0\text{ L}\cdot\text{atm}$

View Correct Answer & Detailed Solution

✓ Correct Option: (B)

Explanation:Pressure-volume work is calculated as $w = -P_{ext} \Delta V$. Here $\Delta V = 5.0 - 2.0 = 3.0\text{ L}$. Thus, $w = -(2.0\text{ atm})(3.0\text{ L}) = -6.0\text{ L}\cdot\text{atm}$.

In a bomb calorimeter operating at constant volume, which thermodynamic quantity is directly measured from heat exchange?

(A)

Enthalpy change ($\Delta H$)

(B)

Internal energy change ($\Delta U$)

(C)

Gibbs free energy ($\Delta G$)

(D)

Total entropy change ($\Delta S$)

View Correct Answer & Detailed Solution

✓ Correct Option: (B)

Explanation:Since volume is constant ($\Delta V = 0$), no expansion work is done ($w = 0$). Therefore, $q_v = \Delta U$, meaning heat measured at constant volume equals the internal energy change.

Q10

By IUPAC convention, which of the following substances has a standard molar enthalpy of formation ($\Delta_f H^\circ$) equal to zero?

(A)

$\text{O}_3(g)$

(B)

$\text{C}(\text{diamond})$

(C)

$\text{O}_2(g)$

(D)

$\text{H}_2\text{O}(l)$

View Correct Answer & Detailed Solution

✓ Correct Option: (C)

Explanation:The standard enthalpy of formation ($\Delta_f H^\circ$) of an element in its most stable physical state at 298 K and 1 bar (such as $\text{O}_2(g)$) is assigned a value of zero.

Q11

Given the following two step reactions:
1) $\text{A} \rightarrow \text{B},\quad \Delta H_1 = +50\text{ kJ}$
2) $\text{B} \rightarrow \text{C},\quad \Delta H_2 = -30\text{ kJ}$
Using Hess's Law, calculate the net enthalpy change ($\Delta H_{net}$) for $\text{A} \rightarrow \text{C}$.

(A)

+80 kJ

(B)

+20 kJ

(C)

-20 kJ

(D)

-80 kJ

View Correct Answer & Detailed Solution

✓ Correct Option: (B)

Explanation:By Hess's Law, adding the two step equations yields $\text{A} \rightarrow \text{C}$ with $\Delta H_{net} = \Delta H_1 + \Delta H_2 = 50 + (-30) = +20\text{ kJ}$.

Q12

An ice cube melts into liquid water in a room maintained at $25^\circ\text{C}$.
What is the sign of the entropy change ($\Delta S$) of the system for this phase transition?

(A)

$\Delta S > 0$

(B)

$\Delta S < 0$

(C)

$\Delta S = 0$

(D)

Cannot be determined

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✓ Correct Option: (A)

Explanation:Liquid water has greater molecular disorder and randomness than crystalline ice, so melting results in an increase in entropy ($\Delta S > 0$).

Q13

A chemical process has an enthalpy change $\Delta H = -40\text{ kJ}$ and an entropy change $\Delta S = -100\text{ J/K}$ at a temperature of 300 K.
Calculate the Gibbs free energy change ($\Delta G$) and determine if the reaction is spontaneous.

(A)

+10 kJ, Non-spontaneous

(B)

-10 kJ, Spontaneous

(C)

-70 kJ, Spontaneous

(D)

+70 kJ, Non-spontaneous

View Correct Answer & Detailed Solution

✓ Correct Option: (B)

Explanation:Convert $\Delta S = -0.100\text{ kJ/K}$. Using $\Delta G = \Delta H - T\Delta S = -40 - (300 \times -0.100) = -40 + 30 = -10\text{ kJ}$. Since $\Delta G < 0$, the process is spontaneous.

Q14

An ideal gas expands inside a rigid, closed steel container with fixed volume ($\Delta V = 0$).
What is the amount of expansion work ($w$) done by the gas during this isochoric process?

(A)

$w = q$

(B)

$w > 0$

(C)

$w = 0$

(D)

$w = \Delta H$

View Correct Answer & Detailed Solution

✓ Correct Option: (C)

Explanation:In an isochoric process, volume remains constant ($\Delta V = 0$). Since $w = -P_{ext}\Delta V$, the expansion work done is zero ($w = 0$).

Q15

What is the standard enthalpy change associated with the complete reaction of 1 mol of $\text{H}^+(aq)$ with 1 mol of $\text{OH}^-(aq)$ to form water called?

(A)

Enthalpy of solution

(B)

Enthalpy of atomization

(C)

Enthalpy of neutralization

(D)

Enthalpy of formation

View Correct Answer & Detailed Solution

✓ Correct Option: (C)

Explanation:The heat released during reaction between an acid and a base to form 1 mole of water is defined as the enthalpy of neutralization.

Q16

Water boils at 373 K under 1 atm with a standard enthalpy of vaporization $\Delta_{vap} H = 40.7\text{ kJ/mol}$.
Calculate the molar entropy of vaporization ($\Delta_{vap} S$) of water at its boiling point.

(A)

$109.1\text{ J}/(\text{mol}\cdot\text{K})$

(B)

$0.109\text{ J}/(\text{mol}\cdot\text{K})$

(C)

$40.7\text{ J}/(\text{mol}\cdot\text{K})$

(D)

$15181\text{ J}/(\text{mol}\cdot\text{K})$

View Correct Answer & Detailed Solution

✓ Correct Option: (A)

Explanation:At phase equilibrium, $\Delta_{vap} S = \frac{\Delta_{vap} H}{T_{boil}} = \frac{40700\text{ J/mol}}{373\text{ K}} \approx 109.1\text{ J}/(\text{mol}\cdot\text{K})$.

Q17

An ideal gas undergoes an isothermal expansion at constant temperature ($T = \text{constant}$).
What is the change in internal energy ($\Delta U$) of the ideal gas?

(A)

$\Delta U > 0$

(B)

$\Delta U < 0$

(C)

$\Delta U = 0$

(D)

$\Delta U = q + P\Delta V$

View Correct Answer & Detailed Solution

✓ Correct Option: (C)

Explanation:For an ideal gas, internal energy depends solely on temperature. In an isothermal process ($\Delta T = 0$), the internal energy remains constant, so $\Delta U = 0$.

Q18

According to the Third Law of Thermodynamics, the entropy of a perfectly crystalline substance approaches zero as temperature approaches:

(A)

$0^\circ\text{C}$

(B)

273.15 K

(C)

0 K

(D)

100 K

View Correct Answer & Detailed Solution

✓ Correct Option: (C)

Explanation:The Third Law states that the entropy of a perfect crystalline structure is zero at absolute zero temperature (0 K).

Q19

Bond Energies:
$\text{H}-\text{H} = 436\text{ kJ/mol}$
$\text{Cl}-\text{Cl} = 242\text{ kJ/mol}$
$\text{H}-\text{Cl} = 431\text{ kJ/mol}$
Calculate the reaction enthalpy ($\Delta_r H$) for: $\text{H}_2(g) + \text{Cl}_2(g) \rightarrow 2\text{HCl}(g)$

(A)

-184 kJ

(B)

+184 kJ

(C)

-247 kJ

(D)

+247 kJ

View Correct Answer & Detailed Solution

✓ Correct Option: (A)

Explanation:$\Delta_r H = \sum \text{Bond Energy (broken)} - \sum \text{Bond Energy (formed)} = (436 + 242) - 2(431) = 678 - 862 = -184\text{ kJ}$.

Q20

Under what combination of enthalpy change ($\Delta H$) and entropy change ($\Delta S$) will a reaction be spontaneous at all temperatures?

(A)

$\Delta H > 0$ and $\Delta S < 0$

(B)

$\Delta H < 0$ and $\Delta S > 0$

(C)

$\Delta H > 0$ and $\Delta S > 0$

(D)

$\Delta H < 0$ and $\Delta S < 0$

View Correct Answer & Detailed Solution

✓ Correct Option: (B)

Explanation:Using $\Delta G = \Delta H - T\Delta S$, if $\Delta H < 0$ (negative) and $\Delta S > 0$ (positive), $\Delta G$ is guaranteed to be negative at all absolute temperatures $T > 0$.

Grade 11 : Chemistry - Thermodynamics (Set 2)

Grade 11 : Chemistry - Thermodynamics (Set 2)— Questions & Detailed Solutions

A chef boils soup in an open steel pot on a gas burner. Steam escapes continuously into the kitchen while thermal energy is supplied from the flame.
Which type of thermodynamic system does the open pot of soup represent?

A gas sample inside a flexible cylinder absorbs 250 J of heat from its environment while expanding against an external piston, doing 100 J of work on the surroundings.
Calculate the change in internal energy ($\Delta U$) of the gas system.

Which of the following physical quantities is classified as a path function rather than a state function?

Which of the following thermodynamic properties is an intensive property?

A chemical hand warmer releases thermal energy into the surroundings when iron powder oxidizes inside a porous pouch.
What is the correct sign of the enthalpy change ($\Delta H$) for this reaction?

A 50 g sample of pure copper (specific heat capacity $c = 0.385\text{ J}/(g\cdot^\circ\text{C})$) is heated, increasing its temperature by $20^\circ\text{C}$.
How much heat energy ($q$) did the copper sample absorb?

A gas contained in a thermally insulated cylinder undergoes a expansion process such that no heat transfers between system and surroundings.
What is the value of heat transfer ($q$) for this adiabatic process?

A gas expands from an initial volume of 2.0 L to a final volume of 5.0 L against a constant external pressure of 2.0 atm.
Calculate the work done ($w$) by the gas in $\text{L}\cdot\text{atm}$.

In a bomb calorimeter operating at constant volume, which thermodynamic quantity is directly measured from heat exchange?

By IUPAC convention, which of the following substances has a standard molar enthalpy of formation ($\Delta_f H^\circ$) equal to zero?

Given the following two step reactions:
1) $\text{A} \rightarrow \text{B},\quad \Delta H_1 = +50\text{ kJ}$
2) $\text{B} \rightarrow \text{C},\quad \Delta H_2 = -30\text{ kJ}$
Using Hess's Law, calculate the net enthalpy change ($\Delta H_{net}$) for $\text{A} \rightarrow \text{C}$.

An ice cube melts into liquid water in a room maintained at $25^\circ\text{C}$.
What is the sign of the entropy change ($\Delta S$) of the system for this phase transition?

A chemical process has an enthalpy change $\Delta H = -40\text{ kJ}$ and an entropy change $\Delta S = -100\text{ J/K}$ at a temperature of 300 K.
Calculate the Gibbs free energy change ($\Delta G$) and determine if the reaction is spontaneous.

An ideal gas expands inside a rigid, closed steel container with fixed volume ($\Delta V = 0$).
What is the amount of expansion work ($w$) done by the gas during this isochoric process?

What is the standard enthalpy change associated with the complete reaction of 1 mol of $\text{H}^+(aq)$ with 1 mol of $\text{OH}^-(aq)$ to form water called?

Water boils at 373 K under 1 atm with a standard enthalpy of vaporization $\Delta_{vap} H = 40.7\text{ kJ/mol}$.
Calculate the molar entropy of vaporization ($\Delta_{vap} S$) of water at its boiling point.

An ideal gas undergoes an isothermal expansion at constant temperature ($T = \text{constant}$).
What is the change in internal energy ($\Delta U$) of the ideal gas?

According to the Third Law of Thermodynamics, the entropy of a perfectly crystalline substance approaches zero as temperature approaches:

Bond Energies:
$\text{H}-\text{H} = 436\text{ kJ/mol}$
$\text{Cl}-\text{Cl} = 242\text{ kJ/mol}$
$\text{H}-\text{Cl} = 431\text{ kJ/mol}$
Calculate the reaction enthalpy ($\Delta_r H$) for: $\text{H}_2(g) + \text{Cl}_2(g) \rightarrow 2\text{HCl}(g)$

Under what combination of enthalpy change ($\Delta H$) and entropy change ($\Delta S$) will a reaction be spontaneous at all temperatures?

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Grade 11 : Chemistry - Thermodynamics (Set 2)

Grade 11 : Chemistry - Thermodynamics (Set 2)— Questions & Detailed Solutions

A chef boils soup in an open steel pot on a gas burner. Steam escapes continuously into the kitchen while thermal energy is supplied from the flame.Which type of thermodynamic system does the open pot of soup represent?

A gas sample inside a flexible cylinder absorbs 250 J of heat from its environment while expanding against an external piston, doing 100 J of work on the surroundings.Calculate the change in internal energy ($\Delta U$) of the gas system.

Which of the following physical quantities is classified as a path function rather than a state function?

Which of the following thermodynamic properties is an intensive property?

A chemical hand warmer releases thermal energy into the surroundings when iron powder oxidizes inside a porous pouch.What is the correct sign of the enthalpy change ($\Delta H$) for this reaction?

A 50 g sample of pure copper (specific heat capacity $c = 0.385\text{ J}/(g\cdot^\circ\text{C})$) is heated, increasing its temperature by $20^\circ\text{C}$.How much heat energy ($q$) did the copper sample absorb?

A gas contained in a thermally insulated cylinder undergoes a expansion process such that no heat transfers between system and surroundings.What is the value of heat transfer ($q$) for this adiabatic process?

A gas expands from an initial volume of 2.0 L to a final volume of 5.0 L against a constant external pressure of 2.0 atm.Calculate the work done ($w$) by the gas in $\text{L}\cdot\text{atm}$.

In a bomb calorimeter operating at constant volume, which thermodynamic quantity is directly measured from heat exchange?

By IUPAC convention, which of the following substances has a standard molar enthalpy of formation ($\Delta_f H^\circ$) equal to zero?

Given the following two step reactions:1) $\text{A} \rightarrow \text{B},\quad \Delta H_1 = +50\text{ kJ}$2) $\text{B} \rightarrow \text{C},\quad \Delta H_2 = -30\text{ kJ}$Using Hess's Law, calculate the net enthalpy change ($\Delta H_{net}$) for $\text{A} \rightarrow \text{C}$.

An ice cube melts into liquid water in a room maintained at $25^\circ\text{C}$.What is the sign of the entropy change ($\Delta S$) of the system for this phase transition?

A chemical process has an enthalpy change $\Delta H = -40\text{ kJ}$ and an entropy change $\Delta S = -100\text{ J/K}$ at a temperature of 300 K.Calculate the Gibbs free energy change ($\Delta G$) and determine if the reaction is spontaneous.

An ideal gas expands inside a rigid, closed steel container with fixed volume ($\Delta V = 0$).What is the amount of expansion work ($w$) done by the gas during this isochoric process?

What is the standard enthalpy change associated with the complete reaction of 1 mol of $\text{H}^+(aq)$ with 1 mol of $\text{OH}^-(aq)$ to form water called?

Water boils at 373 K under 1 atm with a standard enthalpy of vaporization $\Delta_{vap} H = 40.7\text{ kJ/mol}$.Calculate the molar entropy of vaporization ($\Delta_{vap} S$) of water at its boiling point.

An ideal gas undergoes an isothermal expansion at constant temperature ($T = \text{constant}$).What is the change in internal energy ($\Delta U$) of the ideal gas?

According to the Third Law of Thermodynamics, the entropy of a perfectly crystalline substance approaches zero as temperature approaches:

Bond Energies:$\text{H}-\text{H} = 436\text{ kJ/mol}$$\text{Cl}-\text{Cl} = 242\text{ kJ/mol}$$\text{H}-\text{Cl} = 431\text{ kJ/mol}$Calculate the reaction enthalpy ($\Delta_r H$) for: $\text{H}_2(g) + \text{Cl}_2(g) \rightarrow 2\text{HCl}(g)$

Under what combination of enthalpy change ($\Delta H$) and entropy change ($\Delta S$) will a reaction be spontaneous at all temperatures?

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A chef boils soup in an open steel pot on a gas burner. Steam escapes continuously into the kitchen while thermal energy is supplied from the flame.
Which type of thermodynamic system does the open pot of soup represent?

A gas sample inside a flexible cylinder absorbs 250 J of heat from its environment while expanding against an external piston, doing 100 J of work on the surroundings.
Calculate the change in internal energy ($\Delta U$) of the gas system.

A chemical hand warmer releases thermal energy into the surroundings when iron powder oxidizes inside a porous pouch.
What is the correct sign of the enthalpy change ($\Delta H$) for this reaction?

A 50 g sample of pure copper (specific heat capacity $c = 0.385\text{ J}/(g\cdot^\circ\text{C})$) is heated, increasing its temperature by $20^\circ\text{C}$.
How much heat energy ($q$) did the copper sample absorb?

A gas contained in a thermally insulated cylinder undergoes a expansion process such that no heat transfers between system and surroundings.
What is the value of heat transfer ($q$) for this adiabatic process?

A gas expands from an initial volume of 2.0 L to a final volume of 5.0 L against a constant external pressure of 2.0 atm.
Calculate the work done ($w$) by the gas in $\text{L}\cdot\text{atm}$.

Given the following two step reactions:
1) $\text{A} \rightarrow \text{B},\quad \Delta H_1 = +50\text{ kJ}$
2) $\text{B} \rightarrow \text{C},\quad \Delta H_2 = -30\text{ kJ}$
Using Hess's Law, calculate the net enthalpy change ($\Delta H_{net}$) for $\text{A} \rightarrow \text{C}$.

An ice cube melts into liquid water in a room maintained at $25^\circ\text{C}$.
What is the sign of the entropy change ($\Delta S$) of the system for this phase transition?

A chemical process has an enthalpy change $\Delta H = -40\text{ kJ}$ and an entropy change $\Delta S = -100\text{ J/K}$ at a temperature of 300 K.
Calculate the Gibbs free energy change ($\Delta G$) and determine if the reaction is spontaneous.

An ideal gas expands inside a rigid, closed steel container with fixed volume ($\Delta V = 0$).
What is the amount of expansion work ($w$) done by the gas during this isochoric process?

Water boils at 373 K under 1 atm with a standard enthalpy of vaporization $\Delta_{vap} H = 40.7\text{ kJ/mol}$.
Calculate the molar entropy of vaporization ($\Delta_{vap} S$) of water at its boiling point.

An ideal gas undergoes an isothermal expansion at constant temperature ($T = \text{constant}$).
What is the change in internal energy ($\Delta U$) of the ideal gas?

Bond Energies:
$\text{H}-\text{H} = 436\text{ kJ/mol}$
$\text{Cl}-\text{Cl} = 242\text{ kJ/mol}$
$\text{H}-\text{Cl} = 431\text{ kJ/mol}$
Calculate the reaction enthalpy ($\Delta_r H$) for: $\text{H}_2(g) + \text{Cl}_2(g) \rightarrow 2\text{HCl}(g)$