Question

8. What is the heat of reaction when hydrogen and oxygen combine to form water?

Answer 1

Answer:

The heat of reaction when hydrogen and oxygen combine to form water is :

C. 571.6 kJ

Explanation:

Enthalpy Change = The enthalpy change for the formation of 1 mole of the substance from their standard state is called the enthalpy of formation.

This is intensive quantity as it is fixed for 1 mole .

Intensive properties = Those properties which are independent on the amount of the substance are intensive properties.

The value of these quantities does not get halve if you divide the substance into two equal parts. example , density, refractive index.

However , the enthalpy of reaction is extensive. Because on increasing the amount the value of the enthalpy also get doubles

Hence for this reaction :

$2H_{2}(g)+O_{2}\rightarrow 2H_{2}(l)$

Its value is -285.8 kJ for 1 mole

And here two moles are present . so the value of molar enthalpy is:

-285.8 x 2 = -571.6 kJ