Question

The standard enthalpies of formation of $C{O}_2\left(g\right),H_{2}O\left(l\right)$ and glucose(s) at ${25}^{o}C$ are $–400kJ/mol,–300‘kJ/mol$ and $–1300kJ/mol,$ respectively. The standard enthalpy of combustion per gram of glucose at ${25}^{o}C$ is

• A. $+16.11kJ$
• B. $–16.11kJ$
• C. $+2900kJ$
• D. $–2900kJ$

Answer 1

The correct option is B $–16.11kJ$

$C_6{H}_{12}{O}_6\left(s\right)+6O_2\left(g\right)\to 6C{O}_2\left(g\right)+6H_{2}O\left(l\right)$

$\Delta H^o=6(–400)+6(–300)–(–1300)$

$\Delta H^o=–2900kJ/mol$

$\Delta H^o=-\frac{2900}{180}=-16.11kJ/gm$