<span> the atmosphere holds about 21 per cent oxygen. Over the Earth’s 4.6 billion year history, oxygen did not appear in the atmosphere until perhaps about 2.5 billion years ago. Since then, oxygen levels have fluctuated in tandem with global geological and biological events, such as mass extinctions.</span>
I just took a test with this question and got the answer wrong for saying ethane. The correct answer is propane.
<u>Answer:</u> The mass of nitrogen gas reacted to produce given amount of energy is 5.99 grams.
<u>Explanation:</u>
The given chemical reaction follows:

We know that:
Molar mass of nitrogen gas = 28 g/mol
We are given:
Enthalpy change of the reaction = 14.2 kJ
To calculate the mass of nitrogen gas reacted, we use unitary method:
When enthalpy change of the reaction is 66.4 kJ, the mass of nitrogen gas reacted is 28 grams.
So, when enthalpy change of the reaction is 14.2 kJ, the mass of nitrogen gas reacted will be = 
Hence, the mass of nitrogen gas reacted to produce given amount of energy is 5.99 grams.
<h2>
Hello!</h2>
The answer is:
The new temperature will be equal to 4 K.

<h2>
Why?</h2>
We are given the volume, the first temperature and the new volume after the gas is compressed. To calculate the new temperature after the gas was compressed, we need to use Charles's Law.
Charles's Law establishes a relationship between the volume and the temperature at a gas while its pressure is constant.
Now, to calculate the new temperature we need to assume that the pressure is kept constant, otherwise, the problem would not have a solution.
From Charle's Law, we have:

So, we are given the following information:

Then, isolating the new temperature and substituting the given information, we have:




Hence, the new temperature will be equal to 4 K.

Have a nice day!