Consider the following reaction: 2H2 (g) + O2 (g) -> 2H2O (l) delta H = -572 kJ.

Question

Consider the following reaction: 2H2 (g) + O2 (g) -> 2H2O (l) delta H = -572 kJ. a. How much heat is evolved for the production of 1.00 mole H2O (l)? b. How much heat is evolved when 4.03 g hydrogen is reacted with excess oxygen? c. How much heat is evolved when 186 g oxygen is reacted with excess hydrogen? d. the total volume of hydogen gas needed to fill the Hindenburg was 2.0 x10^8 L at 1.0 atm and 25 degrees C. How much heat was evolved when the Hindenburg exploded, assuming all of the hydrogen reacted?

Explanation / Answer

A)

2H2 (g) + O2 (g) -> 2H2O (l)   H = -572 kJ

1 mol of H2O(l)

since the basis is 2 mol, expect half of H

H/2 = -572/2 = 286 kJ

B)

m = 4.03 g of H

mol = mass/MW = 4.03/2 = 2.01 mol

since the basis is 2 mol, H = Hrxn = -572 kJ

C)

m= 186 g of O2

Mol = mass/MW = 186/32 =5.81 mol of O2

1 mol --> -572

5,81 mol --> -572*¨5.81 = -3324.75 kJ

D)

V = H2 gas

V = 2*10^8 L

heat when exploded

PV = nRT

n = PV/(RT)

n = (1)(2*10^8)/(0.082*298) = 8.18*106 mol of H2

2 mol --> -572 kJ

8.18*10^6 = 2.34*10^9 kJ

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