One mole of methanol when burnt in O 2, gives out 723 kJ mol -1 heat. If one mole of O 2 is used, what will be the amount of heat evolved?

Question

One mole of methanol when burnt in O 2, gives out 723 kJ mol -1 heat. If one mole of O 2 is used, what will be the amount of heat evolved? (A) 723 kJ (B) 924 kJ (C) 482 kJ (D) 241 kJ

Tardigrade Admin · Accepted Answer

CH 3 OH (l)+(3/2) O 2(g) longrightarrow CO 2(g)+2 H 2 O (l) Δ H=-723 kJ By burning with (3/2) O 2(g) heat evolved =-723 kJ ∴ By burning with 1 mole O 2(g) =(-723 × 2/3) =-482 kJ

Q. One mole of methanol when burnt in $O_{2}$ , gives out $723 k J m o l^{- 1}$ heat. If one mole of $O_{2}$ is used, what will be the amount of heat evolved?

723 kJ

924 kJ

482 kJ

241 kJ

$C H_{3} O H (l) + \frac{3}{2} O_{2} (g) ⟶ C O_{2} (g) + 2 H_{2} O (l)$
$Δ H = - 723 k J$
By burning with $\frac{3}{2} O_{2} (g)$ heat evolved
$= - 723 k J$
$∴$ By burning with $1$ mole $O_{2} (g) = \frac{- 723 \times 2}{3}$
$= - 482 k J$

Q. One mole of methanol when burnt in O2​, gives out 723kJmol−1 heat. If one mole of O2​ is used, what will be the amount of heat evolved?