According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.
The balanced chemical equation for the reaction is:
Thus if the product is , there are 2 atoms of oxygen. When a coefficient 2 is placed in front of the reactant , there will be 2 atoms of oxygen and 2 atoms of mercury. Thus a coeeficient of 2 is to be added to product side in front of .
remember first there's 2 oxygens so then you check the other side and make it 2 too. then you see that now there's 2Hg and then you put a 2 on the other side to make it 2Hg too. balancing is just making sure the number of elements on one side equal the other.
B is true because plants can only use nitrogen in the form of nitrates, no other living thing needs nitrogen therefore the percentage of nitrogen in the atmosphere is 79%
