How many grams?

Question

If you have a .750 M MgCl2 aqueous solution, How many grams of MgCl2 is present in 425 mL of this solution?

Answer 1

Hi,
1) Okay, so we have .750 mole of MgCl2 in a liter (1000 ml) of water.
2) A mole of MgCl2 weighs 24.31 + 2(35.45) = 95.21 grams.
3) So, we have .750*95.21= 71.41 grams of MgCl2 in 1000 ml of H2O.
4) Then we take out 425 ml of this and we have:
(415/1000)*71.41 = 30.35 grams of MgCl2.

So much for chemistry.:-)

FE

Answer 2

M = molarity = moles of solute per liter of solvent

the molarity and volume are given, so you'll solve for moles.

moles = .750M/.425L = 1.76 moles of MgCl2

now you need to convert moles to grams. so calculate how much 1 mole of MgCl2 is in grams.

Mg= 24.3g
Cl= 35.45 x 2 = 70.9g

then knowing how much 1 mole of MgCl2 weighs, use the conversion factor to solve for grams.

1.76 mol x (95.2g/1mol) = 167.6g of MgCl2