Thermodynamics quiz

Which of these is an intensive property?

For an isolated system:

The work done in free expansion of an ideal gas is:

Delta H is equal to delta U when:

The relation Cp - Cv for one mole of an ideal gas equals:

A reaction is spontaneous at all temperatures when:

The enthalpy of formation of an element in its standard state is:

Which of these is a state function?

The entropy of a perfectly crystalline substance at 0 K is:

In a bomb calorimeter, heat is measured at constant:

What is the IUPAC sign convention for work and heat? (2 marks)

What is an adiabatic process? (2 marks)

Distinguish between extensive and intensive properties. (2 marks)

Define standard enthalpy of combustion with an example. (2 marks)

What is bond enthalpy? (2 marks)

What is lattice enthalpy? (2 marks)

Why does entropy increase when ice melts? (2 marks)

State the second law of thermodynamics in terms of entropy. (2 marks)

How is delta G related to the equilibrium constant? (2 marks)

Why is the enthalpy of neutralisation of a strong acid by a strong base nearly constant? (2 marks)

100 g of water is heated from 25 degrees C to 30 degrees C. Calculate the heat absorbed (specific heat = 4.184 J per g per K). (3 marks)

Calculate delta H for H2(g) + Cl2(g) -> 2HCl(g), given bond enthalpies H-H = 435, Cl-Cl = 242 and H-Cl = 431 kJ/mol. (3 marks)

The enthalpy of vaporisation of water is 40.79 kJ/mol at 373 K. Calculate the entropy of vaporisation. (3 marks)

For a reaction at 298 K, delta G zero = -5.71 kJ/mol. Calculate the equilibrium constant (2.303 RT = 5.71 kJ/mol at 298 K). (3 marks)

A system absorbs 500 J of heat and does 200 J of work on the surroundings. Calculate the change in internal energy. (3 marks)

Read the passage and answer the questions. A student mixed 50 mL of 1 M HCl with 50 mL of 1 M NaOH in an insulated cup. The temperature rose from 25.0 degrees C to 31.7 degrees C. The specific heat of the solution is 4.18 J per g per K and its density is 1.0 g/mL. (i) Calculate the heat released. (ii) Calculate the enthalpy of neutralisation per mole of water formed. (iii) Why is an insulated cup used? (5 marks)

Read the passage and answer the questions. In a car engine, the combustion of petrol releases heat, which expands the gases in the cylinder and pushes the piston. Not all the heat is converted into work; some is lost to the surroundings. (i) Write the first law for this process. (ii) What are the signs of q and w for the gas? (iii) Why can no engine convert all heat into work? (5 marks)

Read the passage and answer the questions. Hess's law states that if a reaction takes place in several steps, its standard reaction enthalpy is the sum of the standard enthalpies of the intermediate reactions at the same temperature. This allows calculation of enthalpies for reactions that cannot be measured directly. (i) Why can the enthalpy of formation of CO not be measured directly? (ii) Which property of enthalpy makes Hess's law possible? (iii) Give one application of Hess's law. (5 marks)

Read the passage and answer the questions. When ammonium nitrate dissolves in water, the solution becomes cold. Yet the process happens spontaneously. Similarly, ice melts spontaneously above 273 K, absorbing heat. (i) Is the dissolution endothermic or exothermic? (ii) What makes these processes spontaneous? (iii) Write the Gibbs energy equation. (5 marks)

Read the passage and answer the questions. The standard enthalpy of formation of a compound is the enthalpy change when one mole of it is formed from its elements in their most stable states. For example, delta fH zero of CO2(g) = -393.5 kJ/mol, of H2O(l) = -285.8 kJ/mol and of CH4(g) = -74.8 kJ/mol. (i) Write the combustion reaction of methane. (ii) Calculate the enthalpy of combustion of methane. (iii) Why is the enthalpy of formation of O2 zero? (5 marks)

Explain the terms system, surroundings, state functions, and types of systems and processes with examples. (6 marks)

State the first law of thermodynamics. Derive the expression for work done in reversible isothermal expansion of an ideal gas. (6 marks)

Define enthalpy. Derive the relation between delta H and delta U. Explain heat capacity and derive Cp - Cv = R. (6 marks)

Explain the different types of enthalpies of reactions with examples. State and explain Hess's law with an example. (6 marks)

Explain spontaneity in terms of entropy and Gibbs energy. Derive the criteria for spontaneity and the relation between delta G zero and K. (6 marks)