#internal energy

Third Law of Thermodynamics and Applications

For the reaction C(s) + O₂(g) → CO₂(g), Δ H = -393.5 kJ/mol at 298 K. What is Δ U? (R = 8.314 J/mol·K)

Δ ng = 1 - 1 = 0, RT = 2.48 kJ, Δ H = Δ U + Δ ng RT, Δ U = -393.5 - 0 = -393.5 kJ/mol.

Ref: NCERT Class 11 Chemistry > Chapter 5: Thermodynamics > Topic: Third Law of Thermodynamics and Applications

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Third Law of Thermodynamics and Applications

For the reaction N₂(g) + 2O₂(g) → 2NO₂(g), Δ H = 66.4 kJ/mol at 298 K, what is Δ U? (R = 8.314 J/mol·K)

Δ ng = 2 - 3 = -1, RT = 2.48 kJ, Δ H = Δ U + Δ ng RT, Δ U = 66.4 - (-1 × 2.48) = 66.4 + 2.48 = 68.88 kJ/mol.

Ref: NCERT Class 11 Chemistry > Chapter 5: Thermodynamics > Topic: Third Law of Thermodynamics and Applications

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Third Law of Thermodynamics and Applications

For the reaction C₂H₂(g) + (5/2)O₂(g) → 2CO₂(g) + H₂O(l) , Δ H = -1299.5 kJ/mol at 298 K. What is Δ U ? ( R = 8.314 J/mo

For Δ ng = 2 - (1 + 2.5) = -1.5 , RT = 8.314 × 298 × 10⁻³ = 2.4776 kJ . Using Δ H = Δ U + Δ ng RT , Δ U = -1299.50 - (-1.5 × 2.4776) = -1299.50 + 3.7164 = -1295.78 kJ/mol .

Ref: NCERT Class 11 Chemistry > Chapter 5: Thermodynamics > Topic: Third Law of Thermodynamics and Applications

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Thermodynamic Terms - System Surroundings and Types of Systems

A system releases 200 J of heat and has 150 J of work done on it. What is Δ U?

Δ U = q + w. Here, q = -200 J (heat released), w = +150 J (work done on system), so Δ U = -200 + 150 = -50 J.

Ref: NCERT Class 11 Chemistry > Chapter 5: Thermodynamics > Topic: Thermodynamic Terms - System Surroundings and Types of Systems

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Thermodynamic Terms - System Surroundings and Types of Systems

For the reaction CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l) , Δ H = -890.00 kJ/mol at 298 K. What is Δ U ? ( R = 8.314 J/mol·K )

For Δ ng = 1 - 3 = -2 , RT = 8.314 × 298 × 10⁻³ = 2.4776 kJ . Using Δ H = Δ U + Δ ng RT , Δ U = -890.00 - (-2 × 2.4776) = -890.00 + 4.9552 = -885.04 ≈ -885.0 kJ/mol .

Ref: NCERT Class 11 Chemistry > Chapter 5: Thermodynamics > Topic: Thermodynamic Terms - System Surroundings and Types of Systems

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Thermodynamic Terms - System Surroundings and Types of Systems

For 2SO₃(g) → 2SO₂(g) + O₂(g) , Δ H = 197.80 kJ/mol at 298 K, what is Δ U ? ( R = 8.314 J/mol·K )

For Δ ng = 3 - 2 = 1 , RT = 8.314 × 298 × 10⁻³ = 2.4776 kJ . Using Δ H = Δ U + Δ ng RT , Δ U = 197.80 - 1 × 2.4776 = 195.32 kJ/mol .

Ref: NCERT Class 11 Chemistry > Chapter 5: Thermodynamics > Topic: Thermodynamic Terms - System Surroundings and Types of Systems

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Thermodynamic Terms - System Surroundings and Types of Systems

In an isobaric process, 600 J of heat is supplied, and the system does 200 J of work. What is Δ U?

At constant pressure, Δ H = qp = 600 J, w = -200 J (work done by system). Δ U = q + w = 600 - 200 = 400 J.

Ref: NCERT Class 11 Chemistry > Chapter 5: Thermodynamics > Topic: Thermodynamic Terms - System Surroundings and Types of Systems

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Thermodynamic Terms - System Surroundings and Types of Systems

A system releases 700 J of heat and performs 400 J of work on the surroundings. What is Δ U?

Δ U = q + w. Here, q = -700 J (heat released), w = -400 J (work done by system), so Δ U = -700 - 400 = -1100 J.

Ref: NCERT Class 11 Chemistry > Chapter 5: Thermodynamics > Topic: Thermodynamic Terms - System Surroundings and Types of Systems

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Heat Capacity and Calorimetry and Measurement of Enthalpy

For an exothermic reaction with Δ H = -100.00 kJ/mol and Δ ng = -1 at 298 K, what is Δ U ? ( R = 8.314 J/mol·K )

For Δ ng = -1 , RT = 8.314 × 298 × 10⁻³ = 2.4776 kJ . Using Δ H = Δ U + Δ ng RT , Δ U = -100.00 - (-1 × 2.4776) = -100.00 + 2.4776 = -97.52 kJ/mol .

Ref: NCERT Class 11 Chemistry > Chapter 5: Thermodynamics > Topic: Heat Capacity and Calorimetry and Measurement of Enthalpy

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Heat Capacity and Calorimetry and Measurement of Enthalpy

The enthalpy of vaporization of a liquid is 32.00 kJ/mol at 350 K. What is Δ U if Δ ng = 1 ? ( R = 8.314 J/mol·K )

For Δ ng = 1 , RT = 8.314 × 350 × 10⁻³ = 2.9099 kJ . Using Δ H = Δ U + Δ ng RT , Δ U = 32.00 - 2.9099 = 29.09 kJ/mol .

Ref: NCERT Class 11 Chemistry > Chapter 5: Thermodynamics > Topic: Heat Capacity and Calorimetry and Measurement of Enthalpy

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Heat Capacity and Calorimetry and Measurement of Enthalpy

For CO(g) + H₂O(g) → CO₂(g) + H₂(g) , Δ H = -41.20 kJ/mol at 298 K, what is Δ U ? ( R = 8.314 J/mol·K )

For Δ ng = 2 - 2 = 0 , Δ H = Δ U + Δ ng RT . Since Δ ng = 0 , Δ U = Δ H = -41.20 kJ/mol .

Ref: NCERT Class 11 Chemistry > Chapter 5: Thermodynamics > Topic: Heat Capacity and Calorimetry and Measurement of Enthalpy

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Heat Capacity and Calorimetry and Measurement of Enthalpy

For the reaction H₂(g) + I₂(g) → 2HI(g), Δ H = 52.96 kJ/mol at 298 K. What is Δ U? (R = 8.314 J/mol·K)

Δ ng = 2 - 2 = 0, so Δ H = Δ U + Δ ng RT = Δ U. Thus, Δ U = 52.96 kJ/mol.

Ref: NCERT Class 11 Chemistry > Chapter 5: Thermodynamics > Topic: Heat Capacity and Calorimetry and Measurement of Enthalpy

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