Question

# 11. Calculate enthalpy of rx using the following information (enthalpy of formation, or enthalpy of rx...

11. Calculate enthalpy of rx using the following information (enthalpy of formation, or enthalpy of rx of other chemical reactions

12. How much energy is released when 2.0 g of methane is combusted in open air (given the enthalpy of reaction).

13. If 1.00 g of ethanol is burned and heats up 100g of water by 5 degrees, what is the heat of combustion of ethanol? (given the specific heat capacity of water)

for methane

CH4 + O2 =CO2 + H2O

balance

CH4 + 2O2 =CO2 + 2H2O

HRXN = Hproducts -Hreactants = -393.5 + 2*-241.8 - (-74.6 + 2*0) = -802.5 kJ/mol

then..

2 g of methane --> mol = masS/MW = 2/16= 0.125

1 mol = 802.5 kJ released

0.125 mol --> 0.125*802.5 = 100.3125 kJ will be released

the... for ethanol

C2H5OH + O2 = CO2 + H2O

balance

C2H5OH + 7/2O2 = 2CO2 + 3H2O

mol of ethanol = mass/MW = 1/46= 0.021739

Q = m*C*(Tf-Ti) = 100*4.184*5 = 2092 J

Hrxn = -2092/0.021739

Hrxn = -96232.57 J/mol = -96.23 kJ/mol