PREPARATION OF SOLUTIONS

Experiment #2CHEM 2

(General & Inorganic

Chemistry)

OBJECTIVE: To prepare solutions of various concentrations.

MATERIALS: 100 ml graduated cylinder 100 ml volumetric flask 500 ml beaker watch glass stirring rod 2 pipette 2 aspirator spatula 5 empty reagent bottles

CHEMICALS (REAGENTS) : concentrated HNO3

CHEMICALS (REAGENTS) : concentrated H2SO4

CHEMICALS (REAGENTS) : concentrated H3PO4

CHEMICALS (REAGENTS) : NaOH pellets

CHEMICALS (REAGENTS) : distilled water

PROCEDURE 1

Prepare 3M, 100cc HNO3 solution using concentrated HNO3 (15.6 N)

PROCEDURE 1

80 mL H2O

19.23 mLconc. HNO3

0.8 mL H2O

graduatedcylinder

beaker

pipette

pipettevolumetric

flask

RESULTS & DISCUSSIONDilution formula:M1 V1 = M2 V215.6 (V1) = 3 (100) (V1) = 300/15.6 = 19.2 mL of conc. HNO3

Volume of conc. HNO3 : ____________Volume of H2O : __________________Molecular mass of HNO3 : __________Mole of solute (HNO3) : ____________

80.8 mL63 g/mol

19.2 mL

0.3 mol

Nitric Acids’ Properties : Molecular formula : HNO3 Apperance : colorless liquid

Solubility in water : completely miscible Other characteristics: highly corossive acid made by reaction of NO2 and water

From 19.23 mL of concentrated HNO3 and 80.8 mL of water, the solution that we produced by using the dilution method (Weakening or reducing the concentration by the addition of water) is 3M nitric acid solution (dilute).

PROCEDURE 2

Prepare 1.5M, 100cc H2SO4 solution using concentrated H2SO4 (36N).

PROCEDURE 2

91.7 mL H2O

8.3 mLconc. H2SO4

graduatedcylinder

beaker

pipette

volumetricflask

RESULTS & DISCUSSIONDilution formula:M1 V1 = M2 V218 (V1) = 1.5 (100) (V1) = 150/18 = 8.3 mL of conc. H2SO4

Volume of conc. H2SO4 : ____________Volume of H2O : __________________Molecular mass of H2SO4 : __________Mole of solute (H2SO4) : _______

8.3 mL91.7 mL

98 g/mol0.15mol

Sulfurc Acids’ Properties : Molecular formula : H2SO4

Apperance : clear, colorless to slightly yellow viscous and odorless liquid

Solubility in water : miscible Other characteristics: non-flammable but highly corossive. It is pungent-ethereal. It is also soluble in water in all concentrations.

From 8.3 mL of concentrated H2SO4 and 91.7 mL of water, the solution that we produced by using the dilution method (Weakening or reducing the concentration by the addition of water) is 1.5M sulfuric acid solution (dilute).

PROCEDURE 3

Prepare of 0.5N, 100cc H3PO4 solution using concentrated H3PO4 (44.4 N)

PROCEDURE 3

98.9 mL H2O

1.1 mLconc. H3PO4

graduatedcylinder

beaker

pipette

volumetricflask

RESULTS & DISCUSSIONDilution formula:N1 V1 = N2 V244.4 (V1) = 0.5 (100) (V1) = 0.5 (100) / 44.4 = 1.1 mL of conc. H3PO4

Volume of conc. H3PO4 : ____________Volume of H2O : __________________Molecular mass of H3PO4 : __________Mole of solute (H3PO4) : ____________Mass of H3PO4 : __________

1.1 mL98.9 mL 97.97 g/mol

1.64 g

Phosporic Acids’ Properties : Molecular formula : H3PO4

Apperance : viscous and colorless liquid Solubility in water : miscible

Other characteristics: deliquescent, non-toxic acid which, in pure, is solid.

From 1.1 mL of concentrated H3PO4 and 98.9 mL of water, the solution that we produced by using the dilution method (Weakening or reducing the concentration by the addition of water) is 0.5N phosphoric acid solution (dilute).

PROCEDURE 4

Prepare 5% 100cc NaOH solution.

PROCEDURE 45 g NaOH

pellets

Add 5 mL of distilled H2O

weigh an emptywatch glass

Dissolve in 90 mL distilled water

stir volumetricflask

beaker

Until obtaining 100 mL of 5% NaOH solution

RESULTS & DISCUSSION

Mass of NaOH pellets : ____________Volume of H2O : __________________

5 g95 mL

Using solubility method...

Sodium Hydroxide’s Properties : Molecular formula : NaOH pellets

Apperance : white, waxy, opaque crystals, odorless Solubility in water : miscible Other characteristics: caustic, readily absorb moist when exposed.

From 5 g of NaOH pellets and 95 mL of water, the solution that we produced by using the dissolution method is 5% sodium hydroxide solution (dilute).

PROCEDURE 5

Prepare 25%, 100cc NaOH solution.

PROCEDURE 525 g NaOH

pellets

Add 5 mL of distilled H2O

weigh an emptywatch glass

Dissolve in 70 mL distilled water

stir volumetricflask

beaker

Until obtaining 100 mL of 5% NaOH solution

RESULTS & DISCUSSION

Mass of NaOH pellets : ____________Volume of H2O : __________________

25 g75 mL

Sodium Hydroxide’s Properties : Molecular formula : NaOH

Apperance : white, waxy, opaque crystals, odorless Solubility in water : miscible Other characteristics: caustic, readily absorb moist when exposed.

From 25 g of NaOH pellets and 80 mL of water, the solution that we produced by using the dilution method (Weakening or reducing the concentration by the addition of water) is 25% sodium hydroxide solution (dilute).

PROCEDURE 6

Repeat procedure 4 and solve for the molality of solution.

SOLVINGMolality:m = nA = wtA = 5g = 0.125 mol kgB mwA 40g/mol 0.095 kg kgB 0.095 kg

= 1.32 m

Volume of solution (L) : __0.1 L________________

Molecular mass of NaOH : __________Mole of solute (NaOH) : ____________

Mass of solvent (kg) : ______0.095 kg____________Molar concentration (m) : _____1.25 M_______

40 g/mol0.125 mol

VALUES LEARNED When making chemical solutions, always use the

appropriate safety equipment. As a general rule, always add the more concentrated

solution to the less concentrated solution. All chemicals that you are unfamiliar with should be

treated with extreme care and assumed to be highly flammable and toxic.

Label all prepared acid solutions before storing them with at least the name of the acid, concentration, hazard warning or how the acid can hurt you, and date prepared on the label.

GENERALIZATION in experiment 1, we have prepared 3M nitric

acid by using dilution method where we added 80.8 mL of H2O to 19.23 mL conc. nitric acid.

in experiment 2, we have prepared 1.5M sulfuric acid by using dilution method where we added 91.7 mL of H2O to 8.3 mL conc. sulfuric acid.

in experiment 3, we have prepared 0.5N phosphoric acid by using dilution method where we added 98.9 mL of H2O to 1.1 mL conc. phosphoric acid.In the first three experiment, we have used the dilution method. It is the process where we weakens the concentration of the substance, but the amount of solute does not change.

GENERALIZATION : in experiment 4, we have prepared 5%

sodium hydroxide solution by dissolving 5g NaOH pellets in 95 mL distilled H2O.

in experiment 5, we have prepared 25% sodium hydroxide solution by dissolving 25g NaOH pellets in 75 mL distilled H2O.

In the last two experiments, we have used the solubility method where a amount of substance is dissolved in a given quantity of solvent to form a saturated solution.

REFERENCES: http://

en.wikipedia.org/wiki/preparingsolutions Modules in GENERAL CHEMISTRY

(Inorganic and Organic)