Concept explainers
Peanuts and peanut oil are organic materials and bum in air. How many burning peanuts does it take to provide the energy to boil a cup of water (250 mL of water)? To solve this problem, we assume each peanut, with an average mass of 0.73 g, is 49% peanut oil and 21% starch; the remainder is noncombustible We further assume peanut oil is palmitic acid, C16H32O2, with an enthalpy of formation of −848.4 kJ/mol. Starch is a long chain of C6H10O5 units, each unit having an enthalpy of formation of −960 kJ.
Interpretation:
To identify how many burning peanuts are required to boil
Concept Introduction:
Heat energy required to raise the temperature of 1g of substance by 1K.Energy gained or lost can be calculated using the below equation.
Where, q= energy gained or lost for a given mass of substance (m), C =specific heat capacity,
The enthalpy of combustion can be calculated as
Answer to Problem 110SCQ
The number of peanuts required is
Explanation of Solution
Given
Given
Molecular weight of starch=
So we have
Enthalpy of combustion of palmitic acid.is calculated as,
Substitute in
Enthalpy of combustion of starch.is calculated as
Since we have
=
We have
Since we have
=
Mass of
Substitute in
Energy required to raise the temperature to
=
=
The total energy =
The total amount of energy released per peanut=
Therefore,
The number of peanuts are required to boil
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Chapter 5 Solutions
EP CHEMISTRY+CHEMICAL REACTIVITY-OWLV2
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