What is the molarity of 5.15 g Mn(NO3)2⋅2H2O in 175 mL of solution

Question

I'm not sure what I'm supposed to do with the 2H2O. Does it get included with the molecular weight when you convert from grams to moles?

Answer 1

Yes, it does get included with the molecular weight as it is actually part of the compound you are weighing out.

The molar mass of Mn(NO₃)₂ • 2H₂O = 314.98 g / mole

5.15 g x 1 mol / 314.98 g = 0.01635 moles of Mn(NO₃)₂ • 2H₂O

175 mls = 0.175 L

Molarity = 0.01635 mols / 0.175 L = 0.0934 M (3 sig. figs.)