Question

1. Describe the preparation of the following solutions. Include the calculations and the necessary laboratory equipment.

A.500 mL of a 1.50 M KNO3 solution.

B. 150g of a 50% solution of NaC2H3O2

c. 500 mL of a 0.50M NaOH solution from a 6.0M NaOH solution.

2. Fifty milliliters of HNO3 require 35.50 mL of Ba(OH)2 0.150M to neutralize. Determine the molarity of the acidic solution. Write the adjusted chemical equation

3. A sample of ten milliliters (10mL) of a KBr solution has a mass of 12.60g. When the solution evaporates, the residue weighs 3.80g, with these data determine a) the density of the solution b) the% by mass of solute c) the molarity of the solution.

Answer 1

1. Describe the preparation of the following solutions. Include the calculations and the necessary laboratory equipment.

A.500 mL of a 1.50 M KNO3 solution.

Solution :- Using the molarity and volume we can find the moles of KNO3 and then convert moles to mass

Moles = molarity x volume in liter

Moles of KNO3 = 1.50 mol per L * 0.500 L

                            = 0.750 mol KNO3

Mass = moles x molar mass

Mass of KNO3 = 0.75 mol * 101.1032 g per mol

                         = 75.8 g KNO3

Therefore we need to use 75.8 g KNO3 and dissolve in small amount of water and then dilute it in the 500 ml volumetric flask up to the mark.

B. 150g of a 50% solution of NaC2H3O2

Solution :-

50 % solution means 50 g solute in 100 g solution

Therefore to make the 150 g solution we need to calculate the mass of NaC2H3O2

150 g * 50 % / 100 % = 75 g NaC2H3O2

Mass of water = mass solution – mass of solute

                       = 150 g – 75.0 g

                        =75.0 g

Therefore we need to use 75 g NaHCO3 and dissolve it in 75 ml water (density of water is 1 g/ml)

c. 500 mL of a 0.50M NaOH solution from a 6.0M NaOH solution.

Solution :- Here we need to use the dilution formula to calculate the volume of the 6.0 M NaOH solution needed to make the 500 ml of 0.50 M NaOH

M1V1=M2V2

V1=M2V2/M1

    = 0.50 M * 500 ml / 6.0 M

   = 41.7 ml

Therefore we need to use 41.7 ml 6.0 M NaOH solution and dilute it with water to make the 500 ml solution.