First, we have to remember the molarity formula:

Part 1:
In this case, our solute is sodium nitrate (NaNO3), and we have the mass dissolved in water, then we have to convert grams to moles. For that, we need the molecular weight:

Then, we calculate the moles present in the solution:

Now, we have the necessary data to calculate the molarity (with the solution volume of 200 mL):

The molarity of this solution equals 0.2339 M.
Part 2:
In this case, we have the same amount (in moles and mass) of sodium nitrate, but a different volume of solution, then we only have to change it:

So, the molarity of this solution is 0.1701 M.
Answer:
A is the answer. Ca(calcium) is an element, O2 is a diatomic element, and NaCl is a compound composed of Na(sodium) and Cl(chlorine)
Explanation:
hopefully that helps!!!
Explanation:
According to the law of conservation of mass, mass can neither be created nor destroyed but it can simply be transformed from one form to another.
For example, 
Mass of Na = 23 g/mol
Mass of Cl = 35.5 g/mol
Sum of mass of reactants = mass of Na + mass of Cl
= 23 + 35.5 g/mol
= 58.5 g/mol
Mass of product formed is as follows.
Mass of NaCl = mass of Na + mass of Cl
= (23 g/mol + 35.5) g/mol
= 58.5 g/mol
As mass reacted is equal to the amount of mass formed. This shows that mass is conserved.
As a result, law of conservation of mass is obeyed.
Pure magnesium's formula would just be Mg because all elements except for 7 nonmetals are just left alone when they are by themselves in a formula. The 7 diatomic elements( means they have to have two of them without another element attached to it aka. a subscript two after it when it's by itself) are hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine. An easy way to remember the diatomic seven is that when looking at a periodic table if you trace over them from nitrogen over to fluorine and down to iodine all of those elements are diatomic + hydrogen.
And your unbalanced and balanced equations are correct.
(sorry I went on a tangent with the diatomic rules hopefully it will help you in the future though)
<span>An aqueous solution is produced when a solute dissolves in water. The biggest responsible is the water that is the solvent of substances in smaller proportion as some ions of K +, Na +, Cl -, forming true solutions. Occurs when a solute dissolves in the water solvent, the separation between the substances is atomic, molecular or ionic, depending on the solution.</span>