The given question is incomplete. The complete question is :
What is the coefficient of
when the following equation is properly balanced with the smallest set of whole numbers? 
Answer: The coefficient of
is 3
Explanation:
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 reaction is:

The coefficient of
is 3
Answer:
A
Explanation:
the number of molecule won't be twice as fructose has 12 hydrogen molecules and lactose has 22 hydrogen molecules
Answer:
Mg(s) + 2H^+(aq) ----> Mg^2+(aq) + H2(g)
Explanation:
We must first write the molecular equation, then obtain the complete ionic equation and subsequently get the net ionic equation as shown below;
Molecular reaction equation;
Mg(s) + 2HCl(aq) ------> MgCl2(aq) + H2(g)
Complete ionic equation;
Mg(s) + 2H^+(aq) + 2Cl^-(aq) ----> Mg^2+(aq) + 2Cl^-(aq) + H2(g)
Net ionic equation;
Mg(s) + 2H^+(aq) ----> Mg^2+(aq) + H2(g)
Na and Cl together form the compound
NaCl2