Question

Calculate the grams of solute needed to prepare each of the following

A) 4.00 L of a 5.00 M NaOH solution

B) 3.50 L of a 0.350 M KCl

C) 50.0 mL of a 7.50 M HCl

Answer 1

A) 4.00 L of a 5.00 M NaOH solution

molarity = W*1000/G.M.wt* volume of solution in L

5             = W*1000/40*4

W            = 5*40*4/1000   = 0.8g

weight of solute ( NaOH) = 0.8g

B) 3.50 L of a 0.350 M KCl

molarity = W*1000/G.M.wt* volume of solution in L

0.35             = W*1000/36.5*3.5

W                = 0.35*36.5*3.5/1000   = 0.0447g

weight of solute (HCl) = 0.0447g

C) 50.0 mL of a 7.50 M HCl

molarity = W*1000/G.M.wt* volume of solution in L

7.5            = W*1000/36.5*0.05

W               = 7.7*36.5*0.05/1000    = 0.014g

weight of solute ( HCl) = 0.014g