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

The 15.230 g of this compound.

Step-by-step 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*(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
`(230.90)/(15.160)* 1=15.230` gram of compound

Hence, The 15.230 g of this compound.

Answer 2

`m=15.2301\ g`

Step-by-step 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=(1250)/(82.45)`

`\dot E=15.1607\ kJ.g^(-1)`

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

`m=(230.9)/(15.1607)`

`m=15.2301\ g`