Question

How much energy is released when 14.0 g of carbon monoxide is completely combusted?

$$\Delta H=-560kJ \\\$$

Answer 1

When a substance is reacted with oxygen gas, it releases energy in the form of heat and light. This reaction is called a combustion reaction. The energy released or absorbed in a combustion reaction is called the enthalpy change of the combustion.

Complete step-by-step answer: To solve this question, we first need to understand the concept of mole ratio.
A conversion factor that relates the number of moles of any two components of a chemical reaction is known as the mole ratio. The coefficients in a balanced chemical equation of a reaction are used to determine the numbers in a conversion factor.
In the given reaction we can see that two moles of carbon monoxide gas combine with one mole of oxygen gas to form two moles of carbon dioxide.
Now, we know that the molar mass of CO = 28g/mol, ${{O}_{2}}=32g/mol$ and $C{{O}_{2}}=44g/mol$.
It is given to us that 14g of carbon monoxide gas is combusted in this reaction, which is equal to 0.5 mol of carbon monoxide.
According to the mole ratio concept, different relative amounts of reactants and products can also be considered by using the same proportionality,
So, we can also say that when 14g of carbon monoxide is completely combusted, 0.5 mol of carbon monoxide gas combines with 0.25 mole of oxygen gas to form 0.5 mol of carbon dioxide.
It is also given to us that $\Delta H=-560kJ$. That means when 2 moles of carbon monoxide gas are combusted in this reaction, the energy released is equivalent to 560kJ.
So, when 0.5 mol of carbon monoxide gas is combusted, the energy released will be
$\Delta H=0.5\times \dfrac{-560}{2}kJ=-140kJ$
Hence, 140kJ of energy is released when 14g of carbon monoxide is completely combusted in a reaction.

Note: It must be noted that the reaction should take place in a constant pressure to calculate the enthalpy change.
Also, negative enthalpy change implies that heat is released in the reaction and the reaction is exothermic. Combustion reactions are always exothermic.