Question

Calculate the molality of a solution formed by dissolving 27.8 g of lii in 500.0 ml of water.

Answer 1

Answer: Molarity of a solution : 0.416 M

$Molarity = \frac{(Moles of solute)}{(Volume of solution in L)}$

In our question LiI(Lithium Iodide) is solute and we need to find the moles of LiI.

Given grams of LiI = 27.8g , Volume of solution = 500 mL

$Moles of LiI = \frac{Grams}{Molar mass}$

Molar mass of LiI = 133.85 g/mol

$Moles of LiI = \frac{27.8g}{133.85\frac{g}{mol}}$

Moles of LiI = 0.208 mol

To find molarity we need volume of solution in 'L' , so we need to convert 500 mL to L.

1 L = 1000 mL

$(500 mL)\times \frac{(1L)}{(1000mL)}$

Volume = 0.5 L

$Molarity = \frac{(Moles of solute)}{(Volume of solution in L)}$

$Molarity = \frac{(0.208mol)}{(0.5 L)}$

Molarity = $0.416\frac{mol}{L}$ or 0.416 M