# Given the standard enthalpy changes for the following two reactions 4 C ( s ) + 5 H 2 ( g ) C...

## Question:

Given the standard enthalpy changes for the following two reactions

{eq}4C(s)+5H_2(g) \rightarrow C_4H_{10}(g), \Delta H^{\circ}=-125.6 kJ {/eq}

{eq}C_2H_4(g) \rightarrow 2C(s)+2H_2(g), \Delta H^{\circ}=-52.3 kJ {/eq},

what is the standard enthalpy change for the reaction

{eq}2C_2H_4(g)+H_2(g) \rightarrow C_4H_{10}(g) {/eq}?

## Hess's Law:

Hess's Law is used to calculate the change in enthalpy of a reaction from provided thermochemical equations. As we need 2 moles of {eq}C_2H_4(g) {/eq} on the reactant side in the required equation and 1 mole of {eq}C_4H_{10}(g) {/eq} on the product side in the required equation, so we can make necessary changes in the given reactions, and then they can be used to determine the enthalpy change of the required reaction.

Become a Study.com member to unlock this answer!

Given the standard enthalpy changes for the following two reactions

{eq}4C(s) + 5H_2(g) \rightarrow C_4H_{10}(g), \Delta H^{\circ}= -125.6 kJ ...

Using Hess's Law to Calculate the Change in Enthalpy of a Reaction

from

Chapter 13 / Lesson 3
26K

Learn about enthalpy of reaction and enthalpy change formula. Understand what Delta H is, the Delta H equation, and how to calculate the enthalpy of reaction.