Question 8 Scoring: 12 points 1000g of water is heated by burning methane gas. (

Question

Question 8 Scoring: 12 points 1000g of water is heated by burning methane gas. (a) Cal culate the heat required to raise the temperature of 1000g of water from 2s'cto 100 C. The specific heat of water is 4.184/eC) (b) Cal e enthalpy of combustion of CH4 is-890.3 kJ/mol. (This means that on of one mole of methane produces 890. 3 kJ of heat energy.) culate the mass of methane required to heat the water. The molar mass of CHsis 16.04 g/mol. The the combustion of one mole (a) Heat required: (b) Mass of methane:

Explanation / Answer

a)
Given:
m = 1000 g
C = 4.184 J/g.oC
Ti = 25 oC
Tf = 100 oC
use:
Q = m*C*(Tf-Ti)
Q = 1000.0*4.184*(100.0-25.0)
Q = 313800 J
Q = 313.8 KJ

b)
1st find the number of mol required
Q = n*Hvap
313.8 KJ = n*890.3 KJ/mol
n = 0.3525 mol

molar mass = 16.04 g/mol

so,
mass = n*molar mass
= 0.3525 mol * 16.04 g/mol
= 5.654 g

Answer:
a) 313.8 KJ
b) 5.654 g

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