Question

The enthalpy of combustion of glucose (mol. wt: $180\, g mol^{-1}$) is $-2840 \,kJ \,mol^{-1}$. Then the amount of heat evolved when $0.9\, g$ of glucose is burnt, will be

• A. $14.2\, kJ$
• B. $14.2\, J$
• C. $28.4\, kJ$
• D. $1420\, kJ$
• E. $142\, kJ$

Answer 1

Answer: (A)

The enthalpy of combustion of glucose (mol. $wt .=180\, g / mol )=-2840\, kJ / mol$

$180\, g$ glucose gives enthalpy of combustion $=2840\, kJ / mol$

1g glucose gives enthalpy of combustion $=\frac{2840}{180}$

So, $0.9\, g$ glucose gives enthalpy of combustion

$=\frac{2840}{180} \times 0.9$

$=\frac{2840}{200} kJ =14.2\, kJ$