Question

Calculate the molarity of each solution.

(1)1.81 mol of LiCl in 32.4 L of solution

(2)0.109 mol of LiNO3 in 6.6 L of solution

(3) 0.0386 mol of glucose in 84.8 mL of solution

To what volume should you dilute 85 mL of a 11.5 M H2SO4 solution to obtain a 1.95 M H2SO4 solution?

Express your answer using two significant figures.

Answer 1

1)

M = mol/Liter

M = 1.81/32.4 = 0.05586

M = 0.05586 mol per liter

2)

M = mol/V

M = 0.109/6.6 = 0.016515 M

3)

V = 84.8 mL = 84.8*10^-3 L

M = mol/L = (0.0386)/(84.8*10^-3) = 0.455 M

Q2.

We need to apply dilution law, which is based on the mass conservation principle

initial mass = final mass

this apply for moles as weel ( if there is no reaction, which is the case )

mol of A initially = mol of A finally

or, for this case

moles of A in stock = moles of A in diluted solution

Recall that

mol of A = Molarity of A * Volume of A

then

moles of A in stock = moles of A in diluted solution

Molarity of A in stock * Volume of A in stock = Molarity of A in diluted solution* Volume of A in diluted solution

Now, substitute known data

M1V1 = M2V2

85*11.5 = 1.95*V

V = 85*11.5 /1.95

Vfinal = 501.28 mL