Question

The enthalpy of combustion of glucose (molecular weight :$130$ $gmo{l}^{-1}$) is $-2840kJ/mol$. Then the amount of heat evolved when $0.9g$ of glucose is burnt, will be:

• A. $14.2kJ$
• B. $1420kJ$
• C. $28.4kJ$
• D. $142kJ$

Answer 1

Answer: (A)

$14.2kJ$

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

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

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

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

$=14.2kJ$