Question

If a pork roast must absorb kJ to fully cook, and if only 10% of the heat produced by the barbecue is actually absorbed by the roast, what mass of is emitted into the atmosphere during the grilling of the pork roast?

Answer 1

1,033.56 grams of carbon dioxide was emitted into the atmosphere.

Step-by-step explanation:

`C_3H_8(g)+5O_2(g)\rightarrow 3CO_2(g)+4H_2O(g),\Delta H_(rxn)=-2044 kJ/mol (assuming)`

Energy absorbed by pork,E =
`1.6* 10^3 kJ` (assuming)

Total energy produced by barbecue = Q

Percentage of energy absorbed by pork = 10%

`10\%=(E)/(Q)* 100`

`Q=(E)/(10)* 100=(1.6* 10^3 kJ)/(10)* 100=1.6* 10^4 kJ`

Since, it is a energy produced in order to indicate the direction of heat produced we will use negative sign.

Q =
`-1.6* 10^4 kJ`

Moles of propane burnt to produce Q energy =n

`n* \Delta H_(rxn)=Q`

`n=(Q)/(\Delta H_(rxn))=(-1.6* 10^4 kJ)/(-2044 kJ/mol)=7.83 mol`

According to reaction , 1 mol of propane gives 3 moles of carbon dioxide. then 7.83 moles of will give:

`(1)/(3)* 7.83 mol=23.49 mol` carbon dioxide gas.

Mass of 23.49 moles of carbon dioxide gas:

23.49 mol × 44 g/mol =1,033.56 g

1,033.56 grams of carbon dioxide was emitted into the atmosphere.