A sample of nitrogen gas kept In a container of volume Is 2.3 L and at a tempera

Question

A sample of nitrogen gas kept In a container of volume Is 2.3 L and at a temperature of 37 degree exerts a pressure of 3.5 atm. Calculate the number of moles of gas present. A chemical equation for conversion of ZnS to ZnO is as follows. delta H for this reaction is -879kJ/mol. Where delta H, ' for ZnO = -348.0 kJ/mol and delta H_f for SO_2 = -296.4kJ/mol Calculate the heat evolved in kJ per gram of ZnS. During volcanic eruptions, hydrogen sulfide gas is given off and oxidized by air according to the following chemical equation: Calculate the standard enthalpy change for the above reaction given:

Explanation / Answer

VII) we will apply ideal gas equation here

PV = nRT

R= gas constant = 0.0821 L-atm / mole K

T = temperature =37 C = 273.15 + 37 K = 310.15 K

P = Pressure = 3.5 atm

V = Volume = 2.3 L

N = number of moles

Number of moles = PV / RT = 3.5 X 2.3 / 0.0821 X 310.15 = 0.316 moles

VIII)

Delta H rxn = [2 X Delta Hf ZnO + 2X Delta HfSO2] –[2 XDelta Hf ZnS + Delta Hf O2]             

Delta Hrxn = -879 = [2 X (-348) + 2 X (-296.4)] – [2 XDelta Hf ZnS +0]

-879 = [-696 – 592.8]-[ 2 XDelta Hf ZnS]

-409.8 = 2 X Delta Hf ZnS

Therefore

Delta Hf ZnS = 204.9 KJ / mole

Molecular weight of ZnS = 97.47 / mole

DeltaHf ZnS = 204.9 / 97.47 KJ / grams = 2.10 KJ /g

IX) the desired equation

2H2S(g) + 3O2(g) --> 2SO2(g) + 2H2O(g) ........(1)

Can be obtained from

3S(s) + 2H2O(g) --> 2H2S + SO2(g)..(2)

S(s) + O2 --> SO2(g)...................(3)

Equation (1) = 3 X equation (3) - Equation (2)

       3S(s) + 3O2 --> 3SO2(g)...................(3)

-     3S(s) + 2H2O(g) --> 2H2S + SO2(g)..(2)

....................................................................

2H2S(g) + 3O2(g) --> 2SO2(g) + 2H2O(g)

............................................................

Delta H (1) = 3 X Delta H(3) - Delta H (2) = 3 (-296.4) - (146.9) = -889.2 - 146.9 = -1036.1 KJ / mole

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