Answer: 
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 equation will be:

Answer: -
Molarity is the term for the concentration expression that relates the moles of solute dissolved in each liter of solution.
Explanation: -
Molarity is defined as number of moles of solute dissolved per litre of the solution.
Molarity symbol is M.
1 M = 1 mol / L
Thus molarity is the term for the concentration expression that relates the moles of solute dissolved in each liter of solution
Answer:
Answer: a) 20g of H2O (18.02 g/mol) molecules=6.68x10^23
Explanation:
In order to find the amount of molecules of each of the options, we need to follow the following equation.

So, let´s get the number of molecules for each of the options.





the smalest number is in option a)
Best of luck.