Question

How much heat is produced by the complete combustion of 280 g of CH4?CH4 (g) +2 02 (9) + CO2 (g) + 2H20 (9) Hrxn = -802.3kJ

Answer 1

-45.95kJ

Explanations:

Given the chemical reaaction between methane and oxygen expressed as:

`CH_4(g)+2O_2(g)\rightarrow CO_2(g)+2H_2O(g)`

From the equation, you can see that Hrxn is negative because the combustion of 280g of methane gives off the heat. Note that the Hrxn is defined for 280 grams of methane.

Find the moles of methane:

`\begin{gathered} Moles=\frac{mass}{molar\text{ mass}} \\ Moles=(280)/(16.04) \\ moles\text{ =17.46moles} \end{gathered}`

If 17.6 moles of methane = -802.3kJ of heat produced

Hence 1 mole of methane will generate:

`\begin{gathered} heat\text{ of CH}_4=(-802.3*1mole)/(17.46moles) \\ heat\text{ of CH}_4=-45.95kJ \end{gathered}`

Therefore the heat produced by the complete combustion of 280 g of CH4 is -45.95kJ. The negative sign shows that heat is given off.