Hess’s Law

Chemistry ⇒ Thermochemistry and Energetics

Hess’s Law starts at 11 and continues till grade 12. QuestionsToday has an evolving set of questions to continuously challenge students so that their knowledge grows in Hess’s Law. How you perform is determined by your score and the time you take. When you play a quiz, your answers are evaluated in concept instead of actual words and definitions used.

See sample questions for grade 11

Describe a situation where Hess’s Law would be necessary to determine the enthalpy change of a reaction.

Describe how you would use Hess’s Law to calculate the enthalpy change for the formation of methane from its elements.

Describe the relationship between Hess’s Law and the concept of state functions.

Describe the steps involved in using Hess’s Law to calculate the enthalpy change of a reaction.

Given the following data: (1) 2C(s) + O₂(g) → 2CO(g), ΔH = -221 kJ (2) 2CO(g) + O₂(g) → 2CO₂(g), ΔH = -566 kJ. Calculate the enthalpy change for 2C(s) + 2O₂(g) → 2CO₂(g).

Given the following data: (1) 2H₂(g) + O₂(g) → 2H₂O(l), ΔH = -572 kJ (2) 2H₂O(l) → 2H₂O(g), ΔH = +88 kJ. Calculate the enthalpy change for 2H₂(g) + O₂(g) → 2H₂O(g).

Given the following data: (1) C(s) + O₂(g) → CO₂(g), ΔH = -393.5 kJ (2) H₂(g) + ½O₂(g) → H₂O(l), ΔH = -285.8 kJ (3) CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l), ΔH = -890.3 kJ. Calculate the enthalpy of formation of CH₄(g).

Given the following data: (1) N₂(g) + O₂(g) → 2NO(g), ΔH = +180 kJ (2) 2NO(g) + O₂(g) → 2NO₂(g), ΔH = -114 kJ. Calculate the enthalpy change for N₂(g) + 2O₂(g) → 2NO₂(g).

Which law is Hess’s Law based on? (1) Law of conservation of mass (2) Law of conservation of energy (3) Law of definite proportions (4) Law of multiple proportions

Which of the following best describes Hess’s Law? (1) The enthalpy change depends on the path taken. (2) The enthalpy change is independent of the path taken. (3) The enthalpy change is always positive. (4) The enthalpy change is always negative.

Which of the following is a correct application of Hess’s Law? (1) Calculating the enthalpy change for a reaction using known enthalpy changes of other reactions. (2) Calculating the mass of a product. (3) Calculating the rate of a reaction. (4) Calculating the pressure of a gas.

Which of the following is a correct statement about Hess’s Law? (1) It is only valid for reactions in the gas phase. (2) It is only valid for reactions at high pressure. (3) It is valid for all chemical reactions regardless of the number of steps. (4) It is only valid for reactions involving oxygen.

Fill in the blank: According to Hess’s Law, the enthalpy change for a reaction is the _______ whether the reaction occurs in one step or several steps.

Fill in the blank: Hess’s Law is a consequence of the _______ of energy.

Fill in the blank: If a reaction is reversed, the sign of ΔH is _______.

Fill in the blank: The enthalpy change for a reaction is a _______ function.

True or False: Hess’s Law can be used to calculate lattice enthalpy.

True or False: Hess’s Law can be used to calculate the enthalpy change for a reaction at any temperature.

True or False: Hess’s Law can be used to calculate the enthalpy of formation of a compound.

True or False: Hess’s Law can be used to determine the enthalpy change of a reaction that cannot be measured directly.