Question

Can anyone help me answer this!?!?!?....Also its finding molarity not moles.

Caluclate how many grams of solid Mg(NO3)2 and Sr(NO3)2 to dissolve in water to make your solutions. Specifically,write out the calculations to prepare 100.0ml of 0.1000M Mg(NO3)2 and 100.0 ml of 0.1000M Sr(NO3)2. --The Mg(NO3)2 supplied comes in the form of Mg(NO3)2 6H2O, use the formula weight 256.4 grams per mole in the calculation for Mg(NO3)2.

Answer 1

Molarity = mol/L
you know that you have
0.1000M and 0.1Litres
so solve for moles

Then use the equation
Mol = g/molecular weight
determine the molecular weight of the two compounds by adding them up then use the moles you have to determine the grams, you know how much of the compound to add to 100mL to achieve the desired concentration

Once you have the grams use gravimeter factor to solve. which is just the ratio of molecular weights of the compound you have and the one you want multiplied by the grams of the compound you need to add into solution.
This will provide you with a number that should be larger and it will equal to the grams of the compound you need

example of equation
(Mg(NO3)2 6H2O/Mg(NO3)2)*grams of Mg(NO3)2 needed to create solution

I'm rusty at solving these equations but once you understand them they are easy.
hope this helps