Quiz for Hess’s law

Q1: Hess’s law is based on which property of enthalpy?

A. State function B. Path function C. Extensive property D. Intensive property

Q2: Hess’s law helps to calculate enthalpy change of:

A. Complex reactions B. Only exothermic reactions C. Only endothermic reactions D. Reactions with no heat change

Q3: If a reaction can be expressed as the sum of two reactions, the enthalpy change of the overall reaction is:

A. Sum of enthalpy changes of the two reactions B. Difference of enthalpy changes C. Product of enthalpy changes D. None of these

Q4: The principle of Hess’s law is used because:

A. Enthalpy is a state function B. Enthalpy is a path function C. Enthalpy depends on reaction speed D. None of these

Q5: Which of these quantities can be calculated using Hess’s law?

A. Enthalpy change of reaction B. Entropy change C. Gibbs free energy D. Activation energy

Q6: If reaction A → B has ΔH = +50 kJ and B → C has ΔH = -20 kJ, then ΔH for A → C is:

A. +30 kJ B. -70 kJ C. +70 kJ D. -30 kJ

Q7: Hess’s law can be applied when reactions are:

A. Carried out in steps B. Carried out in one step only C. At constant pressure only D. At constant volume only

Q8: Which statement about Hess’s law is true?

A. Total enthalpy change is independent of pathway B. Total enthalpy depends on pathway C. Total enthalpy is always zero D. Enthalpy changes add up only at constant volume

Q9: If reaction 1 has ΔH1 and reaction 2 is reversed, what is ΔH for reversed reaction 2?

A. -ΔH2 B. ΔH2 C. Zero D. Same as ΔH1

Q10: Hess’s law is helpful in calculating:

A. Enthalpy change when direct measurement is difficult B. Reaction rate C. Equilibrium constant D. Activation energy

Q11: Which law is Hess’s law consistent with?

A. First law of thermodynamics B. Second law of thermodynamics C. Third law of thermodynamics D. Law of conservation of mass

Q12: The enthalpy change of reaction can be found from Hess’s law using:

A. Standard enthalpy of formation values B. Activation energy values C. Entropy values D. Gibbs free energy values

Q13: Hess’s law applies because enthalpy is a:

A. State function B. Path function C. Extensive function D. None of these

Q14: What does Hess’s law state about enthalpy changes in a cycle?

A. Sum of changes in a cycle is zero B. Sum is maximum C. Sum depends on pathway D. Sum depends on reaction speed

Q15: If a reaction is multiplied by a factor, the enthalpy change:

A. Is multiplied by the same factor B. Remains unchanged C. Is halved D. Becomes zero

Q16: Which process illustrates Hess’s law?

A. Heat of formation from elemental steps B. Rate of reaction measurement C. Equilibrium constant calculation D. Measuring activation energy

Q17: Hess’s law is useful in calculating enthalpy for reactions:

A. Not easy to measure directly B. At equilibrium C. With no heat change D. Very fast reactions

Q18: When combining reactions for Hess’s law, reversed reactions require:

A. Sign change in ΔH B. No change C. Halving ΔH D. Doubling ΔH

Q19: For Hess’s law calculations, enthalpy values should be:

A. Standard enthalpy of formation B. Activation energy C. Heat capacity D. Entropy