### Chemical Reaction General Chemistry – Exam

This exam is about Chemical Reaction General Chemistry – Exam.

The first and second laws of thermodynamics are written below. Complete the sentences by filling in the blanks.

First Law: The energy of the _________ is constant.

Second Law: For any spontaneous process the entropy of the _______ increases.

Universe, Universe

Consider a process in which 220 kJ of work are performed on a gaseous system at 37oC. If at the end of the process the temperature of the system is still 37oC, what can you say about heat involved in this process?

q = -220 kJ

At room temperature the reaction of iron(III) oxide with carbon to produce solid metallic iron and carbon monoxide has K = 10-58 and a positive ΔSo.

2Fe2O3 (s) + 3C (s) → 4Fe (s) + 3CO2 (g)

Despite its very low K value at room temperature this reaction is widely used in industry to convert iron oxide into iron metal at very high temperatures. In fact, more than 100000000 tons of iron is made this way annually. Based on this information, what can we infer about this reaction at very high temperatures?

The value of Δ Ho for the process must be positive and K increases with temperature.

The standard heat of combustion of ethanol, C2H5OH, is 1372 kJ per 1 mole of ethanol. How much heat (in kJ) would be liberated by completely burning a 20.0 g sample of ethanol? (MM(C2H5OH)=46 g/mol)

#### 597 kJ

IF K > 1 for a reaction at 298K what can be said about the reaction at this temperature?

ΔGo < 0

Use the information below to find Δfor the synthesis of ammonia from hydrazine and hydrogen:

N2H4(l) + H2(g) → 2NH3(g)

N2H4(l) + CH4O(l) → CH2O(g) + N2(g) + 3H2(g)    ΔH = -37 kJ

0.5N2(g) + 1.5H2(g) → NH3(g)                                ΔH = -23 kJ

CH4O(l) → CH2O(g) + H2(g)                                    ΔH = -65 kJ

18 kJ

The standard heat of combustion of ethanol, C2H5OH, is 1372 kJ per 1 mole of ethanol. How much heat (in kJ) would be liberated by completely burning a 20.0 g sample of ethanol? (MM(C2H5OH)=46 g/mol)

#### 597 kJ

Imagine you have a 120 g sample of solid tin at 25oC. You add the metal to a crucible and heat it until you have melted all of the tin. If you want to calculate how much heat you needed for this process, which of the following equations would you use?

Some constants you may need:

Sn(s) c = 0.21 J/g-oC

Sn(l) c = 0.050 J/g-oC

c(Sn,fussion) = 59.2 J/g

c(Sn,evaporation) = 2.49 kJ/g MP(Sn) = 232oC

q = 0.21*120*(232-25) + 59.2*120

IF K > 1 for a reaction at 298K what can be said about the reaction at this temperature?

ΔGo < 0

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