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2a. Consider the combustion of propane gas, Propane is often used for gas grills

ID: 1016512 • Letter: 2

Question

2a.

Consider the combustion of propane gas,

Propane is often used for gas grills and is typically purchased by filling a propane tank with 20 pounds of propane. What is the enthalpy change when 10 pound of propane is burned? Use the conversion 1 lb = 454 g and express your answer in scientific notation. For example use 2.3e-5 to indicate a number such as 2.3 x 10-5.

__________kJ

What is the enthalpy change for

Hint, compare this equation to the combustion equation for propane.

________kJ

2b.

Consider the following thermochemical equation:

kJ

2c.

The reaction would be extensive at  ---Select--- at high temperatures at low temperatures at no temperature at all temperatures .

C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(l) Ho = -2,220 kJ/mol

Explanation / Answer

2a]

given 10 pounds of propane

10 pounds = 4540 gms of propane

moles of propane = 4540 / 44 = 103.18

for 1 mole of propane --- > delta H values is -2,220 kJ/mol

103.18 moles of propane have delta H value = -226996 KJ/mol

the enthalpy change in reverse reaction

3 moles of CO2 = delta H value is 2,220 kJ/mol

15 moles of CO2 = 5 * delta H value ==> 11100 KJ/mol

2b] 1mole of CaCO3 absorbs 178 KJ

CaCO3 M.W = 100 gms

moles = 33/100 = 0.33

1 mole 178

0.33 ==> 58.74 KJ/mol

2c]

delta H = Bond energies of reactants - bond energies of products

delta H = 6 N-H bond energy - [3 H-H bond energy + N-N bond energy ]

delta H = 78 KJ/mol

delta S= positive and large

since no. of molecules in products side are more than reactants

therefore randomness increases

the reaction would be extensive at high temperatures

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