Question

Calculate the amount of heat needed to melt 148. g of solid octane (C8H18 ) and bring it to a temperature of 117.8 degrees c. Round your answer to 3 significant digits. Also, be sure your answer contains a unit symbol.

Answer 1

The amount of heat is 84.4894kJ

Step-by-step explanation:

Given data:

mass of octane=148g

The moles of octane is:

`n_(octane) =148g*(1mol)/(114.23g) =1.2956moles`

The melting point is=-56.82°C

ΔHfus=20.73kJ/mol

The heat of fusion is:

`Q_(fus) =n_(octane) *delta-H_(fus) =1.2956*20.73=26.8578kJ`

The heat to bring the octane to a temperature of 117.8°C is:

`Q_(2) =mCp(117.8-(56.82))=148*2.23*(117.8+56.82)=57631.5848J=57.6316kJ`

The total heat in the process is:

Qtotal=Qfus+Q₂=26.8578+57.6316=84.4894kJ