Consider, for example, the reaction 2NO(g)+O2(g)2NO2(g) Then the standard heat o

ID: 579493 • Letter: C

Question

Consider, for example, the reaction

2NO(g)+O2(g)2NO2(g)

Then the standard heat of reaction for the overall reaction is

Hrxn=Hf(products)Hf(reactants)

Hrxn=2(33.2)-[2(90.2)+0]= -114kJ

Part A

For which of the following reactions is Hrxn equal to Hf of the product(s)?

You do not need to look up any values to answer this question.

Check all that apply.

Part B

The combustion of heptane, C7H16, occurs via the reaction

C7H16(g)+11O2(g)7CO2(g)+8H2O(g)

with heat of formation values given by the following table:

Calculate the enthalpy for the combustion of 1 mole of heptane.

Na(s)+12Cl2(l)NaCl(s) 2Na(s)+Cl2(g)2NaCl(s) Na(s)+12Cl2(g)NaCl(s) H2(g)+12O2(g)H2O(g) 2H2(g)+O2(g)2H2O(g) H2O2(g)12O2(g)+H2O(g)

Enthalpy of formation --> must have all elements in their standard state at STP, also, must produce only 1 mol of product required

Na(s)+12Cl2(l)NaCl(s) --> incorrect, Cl2(g) is the correct std. state

2Na(s)+Cl2(g)2NaCl(s) --> not 1 mol of NaCl produced

Na(s)+12Cl2(g)NaCl(s) --> correct

H2(g)+12O2(g)H2O(g) --> correct

2H2(g)+O2(g)2H2O(g) --> not 1 mol of H2O produced

H2O2(g)12O2(g)+H2O(g) --> incorrect, must produce a single mol

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