To calculate the grams of MgCl2 needed, we can use the formula:

Molarity (M) = Mass of solute (in grams) / Volume of solution (in liters)

Rearranging the formula to solve for the mass of solute:

Mass of solute (in grams) = Molarity (M) x Volume of solution (in liters)

Given:

Molarity (M) = 1.4 M

Volume of solution = 700 mL = 0.700 L

Mass of MgCl2 (in grams) = 1.4 M x 0.700 L = 0.98 grams

Therefore, 0.98 grams of MgCl2 are needed to make 700 mL of a 1.4 M solution.