Hess’s Law

Question 1

Which of the following is the best definition of Hess’s law?
A. The mass of the reactants in a chemical reaction is equal to the mass of the products.
B. The enthalpy change of a reaction is equal to the enthalpy of the products minus the enthalpy of the reactants.
C. The enthalpy change of a reaction is the same, regardless of how many steps in the process.
D. The mass of the reactants in a chemical reaction is equal to the mass of the products

Answer 1

C. The enthalpy change of a reaction is the same, regardless of how many steps in the process.

Question 2

What happens to the value of AH for a thermochemical reaction if the
reaction is reversed?
A. AH has the same numerical value, and the sign changes.
B. AH has the same numerical value, and the sign remains the same.
C. AH is the reciprocal of the original value, and the sign changes.
D. AH is the reciprocal of the original value, and the sign remains the same.

Answer 2

A. AH has the same numerical value, and the sign changes.

Question 3

states that if a certain reaction is carried out in a series of steps, the change in enthalpy ΔH for the overall reaction is equals to the sum of the enthalpy changes for the individual steps.

Answer 3

Hess’s Law