Answer:
sample B contains the larger density
Explanation:
Given;
volume of sample A, V = 300 mL = 0.3 L
Molarity of sample A, C = 1 M
volume of sample B, V = 145 mL = 0.145 L
Molarity of sample B, C = 1.5 M
molecular mass of sodium chloride, Nacl = 23 + 35.5 = 58.5 g/mol
Molarity is given as;

The reacting mass for sample A = 0.3mol x 58.5 g/mol = 17.55 g
The reacting mass for sample B = 0.2175 mol x 58.5 g/mol = 12.72 g
The density of sample A 
The density of sample B 
Therefore, sample B contains the larger density
Answer:
- The chemical reaction is not balanced. There is two oxygens on the reactant's side while there's only one oxygen on the products side.
- I would not say it's following the law of conservation of mass as it's not a balanced equation.
- To balance this equation, you would need to add the coefficient of '2' to Magnesium (Mg) on the reactants side, and add the coefficient of '2' to the products side. This would make it so that there's 2 Mg's and 2 O's on both the reactant's side and products side.
edit: I hope this helped you in some way. ^^
C it is combining the nuclei to become bigger