Question

Consider the following reaction:

Answer 1

Answer : The amount of heat transferred in the reaction is 213.4 kJ

Explanation :

Mass of $CH_3OH$ = 27.0 g

Molar mass of $CH_3OH$ = 32 g/mole

Enthalpy of reaction = +252.8 kJ

First we have to calculate the moles of $CH_3OH$.

$\text{ Moles of }CH_3OH=\frac{\text{ Mass of }CH_3OH}{\text{ Molar mass of }CH_3OH}=\frac{27.0g}{32g/mole}=0.844moles$

Now we have to calculate the amount of heat transferred in the reaction.

The given balanced chemical reaction is:

$2CH_3OH(g)\rightarrow 2CH_4(g)+O_2(g)$

From the reaction, we conclude that

As, 2 moles of $CH_3OH$ transfer heat = 252.8 kJ

So, 0.844 moles of $CH_3OH$ transfer heat = 0.844 × (252.8 kJ)

                                                                                      =  213.4 kJ

Therefore, the amount of heat transferred in the reaction is 213.4 kJ

Answer 2

Consider the following reaction: 
2CH3OH(g)→2CH4(g)+O2(g)ΔH=+252.8kJ
Calculate the amount of heat transferred when 27.0g of CH3OH(g) is decomposed by this reaction at constant pressure. 

27.0 g CH3OH(g) (1 mol/ 32.05g) = 0.84 mol CH3OH(g)
ΔH =+252.8kJ = Q = 0.84 mol (252.8kJ) = 213 kJ