Question

calculation the required mass in order to have 250 ml of na2s2o3.5h2o at 38 g/l

Answer 1

Given: Strength = 38g/L (than means 38g of Na2S2O3.5H2O is dissolved in 1L of solution)
Number of moles in 38g of Na2S2O3.5H2O = 38 / 248 = 0.15

Molarity = No of moles of solute / Concentration of solution (inL) = 0.15/1 = 0.15 M

(No of moles = mass of solute / Molecular mass)

Now for 250 mL of solution, from the formula of molarity we will calculate the mass required in 250 mL

0.15 = (m/248)/0.25

m = 0.15x 0.25 x 248 = 9.3g

required mass in order to have 250 ml of na2s2o3.5h2o at 38 g/l is 9.3g