chemistry help.. i just dont get it :(?

Question

1. find the molarity of a solution if 148 grams of sodium hydroxide is dissolved in enough water to make 3.8 L of solution?
2. find the number of grams of Magnesium Nitrate in 5.2 L of a 4.4 molar solution of magnesium nitrate.

Answer 1

1. NaOH = 40 g/m
148g/40g/m = 3.7 moles
3.7m/3.8L = .974 Molarity

2. Mg(NO3)2 = 148 g/m
4.4M = moles Mg(NO3)2/ 5.2 L
(22.88) x (148 g/m) = 3.393 Kg

Answer 2

For both questions, use the two equations

Amount (moles) = concentration (molarity) x volume (L)

Mass (g) = moles x formula weight

This should do it for you. Think about what happens to the concentration when you dilute something. Also, if you have something with higher formula weight (or molar mass or whatever you have been taught to call it), I think you can see that you will need a greater weight of stuff to have the same number of moles.

Good luck!