Question

QUESTION 62 Using the following equation for the combustion of octane, calculate the heat of reaction for 100.0 g of octane. The molar mass of octane is 114.33 g/mole. 2C8H 18 + 25 0 2 - 16 CO 2 +18 H 20 AH® rxn=-11018 kJ 4.82 kJ 4.82 x 103 kJ 9.64 x 103k) 1.26 x 104 kJ

Answer 1

Molar mass of C8H18 = 114.33 g/mol

mass(C8H18)= 100.0 g

use:

number of mol of C8H18,

n = mass of C8H18/molar mass of C8H18

=(100 g)/(114.33 g/mol)

= 0.8755 mol

Since Δ H is positive, heat is absorbed

when 2 mol of C8H18 reacts, heat absorbed = 11018.0 KJ

So,

for 0.8755 mol of C8H18, heat absorbed = 0.8755*11018.0/2 KJ

= 4.82*10^3 KJ

Answer: OPTION 2