Question

The total volume of hydrogen gas needed to fill the hindenburg was 2.00 × 108 l at 1.00 atm and 25.° c. How much energy was evolved when it burned?

Answer 1

Answer : The energy evolved when it burned was, $-2.337\times 10^9KJ$

Solution :

First we have to calculate the moles of hydrogen gas by using ideal gas equation.

$PV=nRT$

where,

P = pressure of gas = 1 atm

V = volume of gas = $2\times 10^8L$

T = temperature of gas = $25^oC=273+25=298K$

R = gas constant = 0.0821 Latm/moleK

n = number of moles of gas

Now put all the given values in the above formula, we get the moles of hydrogen gas.

$(1atm)\times (2\times 10^8L)=n\times (0.0821Latm/moleK)\times (298K)$

$n=8.174\times 10^6moles$

Now we have to calculate the amount of energy evolved.

The combustion reaction of hydrogen will be,

$H_2(g)+\frac{1}{2}O_2(g)\rightarrow H_2O(l)$

The enthalpy of combustion of hydrogen is -286 KJ/mole. (standard value)

As 1 mole of hydrogen gas burned it evolved energy = -286 KJ

So, $8.174\times 10^6moles$ of hydrogen gas burned it evolved energy = $(8.174\times 10^6)\times (-286)=-2.337\times 10^9KJ$

Therefore, the energy evolved when it burned was, $-2.337\times 10^9KJ$