Question

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A. Aluminum has a specific heat of 0.880 J/g-degree. How many joules are needed to heat 725g of aluminum from 20.0^oC to 125.0^oC ?

B. The delta H of combustion of C₂H₆ is 1541kJ/mole. How many kJ of energy result when 700.0g of C₂H₆ are combusted ?

Answer 1

A) Q = m*C*delta T

where, Q = heat

m = mass

C = specific hat capacity

delta T = T2 - T1

Q = 725*0.880*(125 - 20)

Q = 725 * 0.880 * 105 = 66990 J

B)

Balanced equation is

2 C2H6 + 7 O2 ----> 4 CO2 + 6 H2O

number of moles of C2H6 = 700.0g / 30.07 g.mol^-1 = 23.3 mole

2 mole of C2H6 has delta H = 1541 kJ/mole so

23.3 mole of C2H6 will have delta H

= 23.3 mole of C2H6 *(1541 kJ/mole / 2 mole of C2H6)

=17952.7 kJ

Therefore, delta H for 700.0g of C2H6 will be 17952.7 kJ