Question

If the heat of combustion for a specific compound is − 1250.0 kJ / mol and its molar mass is 82.45 g / mol, how many grams of this compound must you burn to release 230.90 kJ of heat?

Answer 1

Answer:

$m=15.2301\ g$

Explanation:

Given:

• heat of combustion, $Q_{ex}=-1250\ kJ.mol^{-1}$ (negative sign means heat is evolved)

• molar mass of the compound, $M=82.45\ g.mol^{-1}$

• Desired heat of combustion, $E=230.9\ kJ$

Now the amount of heat evolved after the combustion of one gram of compound:

$\dot E=\frac{1250}{82.45}$

$\dot E=15.1607\ kJ.g^{-1}$

Therefore the mass of compound burnt to get the desired heat:

$m=\frac{230.9}{15.1607}$

$m=15.2301\ g$

Answer 2

Answer:

The 15.230 g of this compound.

Explanation:

Given that,

Specific compound = -1250.0 kJ

Molar mass = 82.45 g/mol

Heat =230.90 kJ

We need to calculate the mass

We use the enthalpy change of combustion from kJ/mol to kJ/g.

The compound's molar mass equal to the 82.45 kJ/mol.

One mole of this compound has a mass of  82.45 g

$1250.0\ kJ/mol\times\dfrac{1\ mol}{82.45\ g}=15.160\ kJ/g$

Now, complete combustion in one gram is 15.160 kJ.

As, 15.160 kJ of heat release from 1 gram of compound

So, 230.90 kJ of heat release from $\dfrac{230.90}{15.160}\times 1=15.230$ gram of compound

Hence, The 15.230 g of this compound.