The heat of combustion of carbon to $$C{O_2}$$ is $$ - 393.5kJ/mol.$$ The heat released upon the formation of $$35.2\,g$$ of $$C{O_2}$$ from carbon and oxygen gas is
A.
$$ - 315\,kJ$$
B.
$$ + 315\,kJ$$
C.
$$ - 630\,kJ$$
D.
$$ - 3.15\,kJ$$
Answer :
$$ - 315\,kJ$$
Solution :
Given, $$C\left( s \right) + {O_2}\left( g \right) \to C{O_2}\left( g \right);$$
$${\Delta _f}H = - 393.5\,kJ\,mo{l^{ - 1}}$$
$$\because $$ Heat released on formation of $$44g$$ or $$1\,{\text{mole}}$$
$${\text{C}}{{\text{O}}_2} = - 395.5\,kJ\,mol$$
$$\because $$ Heat released on formation of $$35.2{\text{ }}g$$ of $$C{O_2}$$
$$\eqalign{
& = \frac{{ - 393.5\,kJ\,mo{l^{ - 1}}}}{{44g}} \times 35.2\,g \cr
& = - 315\,kJ\,mo{l^{ - 1}} \cr} $$
Releted MCQ Question on Physical Chemistry >> Chemical Thermodynamics
Releted Question 1
The difference between heats of reaction at constant pressure and constant volume for the reaction : $$2{C_6}{H_6}\left( l \right) + 15{O_{2\left( g \right)}} \to $$ $$12C{O_2}\left( g \right) + 6{H_2}O\left( l \right)$$ at $${25^ \circ }C$$ in $$kJ$$ is
$${\text{The}}\,\Delta H_f^0\,{\text{for}}\,C{O_2}\left( g \right),\,CO\left( g \right)\,$$ and $${H_2}O\left( g \right)$$ are $$-393.5,$$ $$-110.5$$ and $$ - 241.8\,kJ\,mo{l^{ - 1}}$$ respectively. The standard enthalpy change ( in $$kJ$$ ) for the reaction $$C{O_2}\left( g \right) + {H_2}\left( g \right) \to CO\left( g \right) + {H_2}O\left( g \right)\,{\text{is}}$$