Enthalpy changes that are difficult to measure directly can often be determined using Hess' Law

to construct an enthalpy cycle.

Which enthalpy change is indicated by X in the enthalpy cycle shown?

C (s) + 2H2 (g) + 2O2 (g)

CH4 (g) + 2O2 (g) CO2 (g) + 2H2O (l)

X

A - 4 * the enthalpy of combustion of hydrogen

B + 4 * the enthalpy of combustion of hydrogen

C - 2 * the enthalpy of formation of water

D + 2 * the enthalpy of formation of water

from may june 14 zone 11 q 3 a levels

Question

Chemistry

Maddox Barron

26 July, 19:49

Enthalpy changes that are difficult to measure directly can often be determined using Hess' Law

to construct an enthalpy cycle.

Which enthalpy change is indicated by X in the enthalpy cycle shown?

C (s) + 2H2 (g) + 2O2 (g)

CH4 (g) + 2O2 (g) CO2 (g) + 2H2O (l)

X

A - 4 * the enthalpy of combustion of hydrogen

B + 4 * the enthalpy of combustion of hydrogen

C - 2 * the enthalpy of formation of water

D + 2 * the enthalpy of formation of water

from may june 14 zone 11 q 3 a levels

+4

Answers (1)

Know the Answer?

Fatima Brown · Answer 1

Hess’ Law states that the heat of formation of the substances is the summation of the products minus the summation of the reactants in a chemical equation.

The change in enthalpy indicated by X is - 2 multiplied by the formation of water. The answer is letter C.