how many grams of MgCl2 would you dissolve in 650mls of water to make a 0.45M solution?

To calculate the number of grams of MgCl2 needed to make a 0.45M solution in 650 mL of water, you need to use the formula:

Molarity (M) = (moles of solute) / (volume of solvent in liters)

First, convert the volume of solvent (water) from milliliters (mL) to liters (L):

650 mL ÷ 1000 = 0.65 L

Now, rearrange the formula to solve for moles of solute:

moles of solute = Molarity (M) × volume of solvent (L)

Substitute the given values:

moles of solute = 0.45 M × 0.65 L

Next, you need to convert moles of MgCl2 to grams. To do this, you need to know the molar mass of MgCl2, which consists of one atom of magnesium (Mg) and two atoms of chlorine (Cl).

The molar mass of Mg is approximately 24.31 g/mol, and the molar mass of Cl is approximately 35.45 g/mol.

Molar mass of MgCl2 = (1 × atomic mass of Mg) + (2 × atomic mass of Cl)
= (1 × 24.31 g/mol) + (2 × 35.45 g/mol)
= 95.21 g/mol

Now, use the molar mass to calculate the grams of MgCl2:

grams of MgCl2 = moles of solute × molar mass of MgCl2

Substitute the values:

grams of MgCl2 = (0.45 M × 0.65 L) × 95.21 g/mol

Now, calculate it:

grams of MgCl2 = 27.94 g

Therefore, to make a 0.45M solution of MgCl2 in 650 mL of water, you would need to dissolve 27.94 grams of MgCl2.