Solveeit Logo
Login

Question

Question: The heat of combustion of carbon is \( - 393.5\;kJmo{l^{ - 1}}\). The heat released upon the formati...

The heat of combustion of carbon is −393.5  kJmol−1 - 393.5\;kJmo{l^{ - 1}}. The heat released upon the formation of 35.2g35.2g of CO2C{O_2} from carbon and oxygen gas is:
(A) +315 kJ + 315\,kJ
(B) −31.5  kJ - 31.5\;kJ
(C) −315 kJ - 315\,kJ
(D) +31.5  kJ + 31.5\;kJ

Explanation

Solution

As we know that heat of combustion or change in enthalpy of combustion is the amount of heat released when 11 mole of compound undergoes complete combustion reaction in the presence of oxygen or we can say that the amount of heat required to form a compound upon burning its elements.

Complete Step by step answer: As we know that heat of combustion or change in enthalpy is that amount of heat which is released when 11 mole of compound undergoes a complete combustion reaction in the presence of oxygen or we can say that change in enthalpy that takes place when 11 mole of product is formed from its elements which are present in their standard state in the most stable allotropic form which we normally call the heat of formation.
We are given the heat of combustion of carbon, so let us first write the equation for combustion of carbon and oxygen to form carbon dioxide.
C+O2→CO2C + {O_2} \to C{O_2}, ΔfH=−393.5  kJ  mol−1{\Delta _f}H = - 393.5\;kJ\;mo{l^{ - 1}}
The heat of formation of carbon or heat of formation of carbon dioxide is −393.5  kJmol−1 - 393.5\;kJmo{l^{ - 1}}. We know that 11 mole of carbon reacts with 11 mole of oxygen to form 11 mole of carbon dioxide or we can say that 22g22g of carbon dioxide reacts with 32g32gof oxygen to form 44g44g of carbon dioxide.
So, heat of formation of 44g44g of carbon dioxide is ΔfH=−393.5  kJ  mol−1{\Delta _f}H = - 393.5\;kJ\;mo{l^{ - 1}}now we can calculate the heat released upon formation of 35.2g35.2gwhich will be:
ΔfH=−393.5×35.244{\Delta _f}H = \dfrac{{ - 393.5 \times 35.2}}{{44}}
⇒ΔfH=−315  kJmol−1\Rightarrow {\Delta _f}H = - 315\;kJmo{l^{ - 1}}

Therefore, the correct answer is (C).

Note: Combustion reactions mostly take place at high temperatures and the energy produced during such reactions is converted to heat or light energy which can be used to heat water, cook food, electricity generation and even can be used to provide the power to vehicles.