In a chemical equation, the sum of the masses
of the products is less than the reactants
of the products is more than the reactants
of the products is equal to the reactants
of the products is not equal to the reactants

of the products is equal to the reactants

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 equation for formation of water :

mass of reactants = mass of hydrogen + mass of oxygen =

mass of product = mass of water =  

what is the general relationship between a galaxy's distance from earth and its speed?

the answer is:

the farther away a galaxy is from us, the faster it is moving away from us.