Thermodynamics and Entropy Concept
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Questions and Answers

What is the equation for work during reversible expansion of an ideal gas?

Vf w rev = - ∫ pin dV

What is the work done during isothermal expansion of an ideal gas into a vacuum?

Zero (w = 0)

For an isothermal irreversible change of an ideal gas, what is the relationship between heat and work?

q = -w = pex (Vf - Vi)

What is the expression for pressure in terms of volume for an ideal gas?

<p>p = nRT/V</p> Signup and view all the answers

What is the work done during adiabatic change of an ideal gas?

<p>w = -nRT ln(Vf/Vi)</p> Signup and view all the answers

In the given scenario, how much heat is absorbed and how much work is done during the isothermal expansion of the gas?

<p>Heat absorbed: 0, Work done: 0</p> Signup and view all the answers

What is the quantity of heat absorbed by the calorimeter in an exothermic reaction?

<p>Negative</p> Signup and view all the answers

What does a negative value of qp indicate in a reaction?

<p>Exothermic nature</p> Signup and view all the answers

What is the formula for calculating the quantity of heat from a reaction?

<p>q = CV × ∆T</p> Signup and view all the answers

What does a positive value of qp indicate in a reaction?

<p>Endothermic nature</p> Signup and view all the answers

What is the enthalpy change for the combustion of 1 mol of graphite?

<p>-2.48 × 10^2 kJ mol^–1</p> Signup and view all the answers

What is the relationship between ∆U and ∆H when ∆ng = 0?

<p>∆ H = ∆ U</p> Signup and view all the answers

What is the reason why reactions are often carried out at high temperature?

<p>The positive entropy change of the system can be 'small', in which case T must be large.</p> Signup and view all the answers

What is the natural direction of a spontaneous change in an isolated system?

<p>Increase in entropy</p> Signup and view all the answers

How does the second law of thermodynamics explain the common occurrence of spontaneous exothermic reactions?

<p>By stating that heat released by the reaction increases the disorder of the surroundings, leading to a positive overall entropy change.</p> Signup and view all the answers

What are the three types of molecular motions that contribute to entropy increase with rising temperature?

<p>Translational, rotational, and vibrational motion</p> Signup and view all the answers

What happens to entropy when the temperature of a system rises?

<p>Entropy increases</p> Signup and view all the answers

What happens to entropy when the temperature of a system is lowered?

<p>Entropy decreases</p> Signup and view all the answers

What is entropy in the context of thermodynamics?

<p>Entropy is a measure of the degree of randomness or disorder in a system.</p> Signup and view all the answers

How does entropy change in relation to the disorder in an isolated system?

<p>The higher the disorder in an isolated system, the higher the entropy.</p> Signup and view all the answers

What does an increase in entropy in a chemical reaction signify?

<p>An increase in entropy in a chemical reaction indicates a higher disorder in the products compared to the reactants.</p> Signup and view all the answers

How can entropy change be estimated qualitatively in a chemical reaction?

<p>Entropy change in a chemical reaction can be estimated by considering the structures of the species involved.</p> Signup and view all the answers

What state of a substance has the lowest entropy?

<p>The crystalline solid state has the lowest entropy.</p> Signup and view all the answers

Which state of a substance has the highest entropy?

<p>The gaseous state has the highest entropy.</p> Signup and view all the answers

What is the standard enthalpy of formation of NH3 gas?

<p>-92.4 kJ mol–1</p> Signup and view all the answers

Calculate the standard enthalpy of formation of CH3OH(l) using the given data.

<p>-238.5 kJ mol–1</p> Signup and view all the answers

Calculate the enthalpy change for the process CCl4(g) → C(g) + 4 Cl(g) and the bond enthalpy of C – Cl in CCl4(g).

<p>∆H = 485.0 kJ mol–1, Bond enthalpy of C – Cl = 121.25 kJ mol–1</p> Signup and view all the answers

For an isolated system with ∆U = 0, what is the value of ∆S?

<p>0</p> Signup and view all the answers

At what temperature will the reaction 2A + B → C become spontaneous given ∆H and ∆S values?

<p>T &gt; 2000 K</p> Signup and view all the answers

What are the signs of ∆H and ∆S for the reaction 2 Cl(g) → Cl2(g)?

<p>∆H = 0, ∆S &gt; 0</p> Signup and view all the answers

Calculate ∆G for the reaction 2 A(g) + B(g) → 2D(g) and predict its spontaneity.

<p>-10.5 kJ, Non-spontaneous</p> Signup and view all the answers

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