I hate stoichiometry. I will help you but I need to know the question first.
Because Air itself is not an element. it is made up by different elements such as Oxygen and nitrogen. since its made up of a mix of different elements, its rather a homogeneous mixture :)
Scientific investigation: The process in which scientist solve the question by using different systematic approach. It can be initiated in different ways.
Experimental Scientific investigation: The investigation in which scientist answer the question on the basis of experimental results. Experimental investigation includes both dependent and independent variables, and only one variable is tested at a time is possible.
The best example of an experimental scientific investigation is: when we placed a whole apple and apple slice under sun, and noted down how many days it will take to rot in order to compare the break down of apple slice and whole apple.
Thus, option (B) is the correct answer.
Answer:
3000 kJ/kg
Explanation:
The calorific value of a substance is the amount of heat produced per unit mass by the combustion of the substance.
It is given by:

where
Q is the amount of heat released
m is the mass of the fuel
In this problem, we have:
m = 60 kg is the mass of fuel
is the amount of heat released
Therefore, the calorific value of the fuel is:

Unfortunately, we have not fully solved the 'nitrogen problem'. To do this, we must halve the amount of nitrogen we dump into the environment by mid-century or our ecosystems will face epidemics of toxic tides, lifeless rivers, and dead oceans. And that to do that will require, among other things, almost doubling the efficiency of nitrogen use on the world’s farms.