Experiment 2 Dilution

EXPERIMENT 2: DILUTION Objectives: To determine the concentration of coloured solution such as FeCl3 by using dilution and colour differentianting (colorimetric) techniques. Concepts: 1. To understand molarity,normality and mole concepts 2. To learn dilution techniques 3. To learn the way to use M1V1=M2V2 Introduction: Concentration can be expressed in many different ways such as percentages volume and percentage weight etc. In laboratory, normally concentrations were expressed as molarity and normality. Molarity is the mole of material in 1000 mL (1 Liter or 1 dm3) of solution, as shown as followed equation. Molarity (M) = Mole_________ Volume ( 1 Liter/ 1 dm3) M = n/V Stock solution is the solution with known concentration. When the solution was diluted, only the concentrations will change while the mole number is remain constant. Based on this principle, the concentration of dilute solution can be determined by using followed equation. M1V1 = M2V2

Where: M1= concentration of concentrated solution (mol dm3) V1= volume of concentrated solution (dm3) M2= concentration of dilute solution V2= volume of dilute solution Apparatus: Pipette Test Tube

6 unit

Volumetric flask.

5 × (50/100)

Materials: 0.10 M FeCl3 solution 0.10 KCNS solution FeCl3 solution (B) Methods: 1. Calculate and prepared the following solution from standard solution of 0.01 M FeCl3, by a given equation a. 50/100 ml FeCl3 solution ( 5.0 × 10-2 M) b. 50/100 ml FeCl3 solution ( 5.0 × 10-2 M) c. 50/100 ml FeCl3 solution ( 5.0 × 10- 3M) d. 50/100 ml FeCl3 solution ( 5.0 × 10-3M) e. 50/100 ml FeCl3 solution ( 5.0 × 10-4 M) The Volume of solution is recorded. 2. 5 ml of each prepared solution are transfer into test tube and add 2 drop of KCNS (potassium thiocyanate) to each test tube. Shake it until homogeneous and wait for any colour changes.

3. 5 ml of B solution are transfer into another test tube and add 2 drop of KCNS solution. Shake it and compare colour of the solution with the series of solution that have been prepared previously (2). Suggest the concentration of B solution. Result: (A) For 50ml solution. By using M1V1 = M2V2 (a.) (0.1) (V1) = (50)(5.0 × 10-2 M) (V1) = 25 ml (b.) (0.1) (V1) = (50)(1.0 × 10-3 M) (V1) = 5 ml (c.) (1.0 × 10 -2) (V1)= (50)(5.0 × 10-3) (V1) = 25 ml (d.) (V1) (5.0 × 10-3 ) = (50)(5.0 × 10-3 M) (V1) = 10 ml (e.) (V1) (5.0 × 10-3 M )= (50)(5.0 × 10-4 M) (V1) = 25 ml

(B) For 100 mL By using M1V1 = M2V2 (e.) (0.1) (V1) = (100)(5.0 × 10-2 M) (V1) = 50 ml (f.) (0.1) (V1) = (100)(1.0 × 10-3 M) (V1) = 10 ml

(g.) (0.1) (V1)= (100)(5.0 × 10-3) (V1) = 5 ml (h.) (V1) (5.0 × 10-3 ) = (100)(1.0 × 10-3 M) (V1) = 20 ml (e.) (V1) (1.0 × 10-3 M) = (100)(5.0 × 10-4 M) (V1) = 50 ml Concentration of unknown B solution is: 1.0 × 10-3 M

Discussion: Dilution also defines as the process where the concentration is the measure of how much of a given substance there is mixed with another substance. This can apply to any sort of chemical mixture, but most frequently the concept is limited to homogeneous solutions, where it refers to the amount of solute in a substance. To concentrate a solution, one must add more solute, or reduce the amount of solvent (for instance, by selective evaporation). By contrast, to dilute a solution, one must add more solvent, or reduce the amount of solute. Unless two substances are fully miscible there exists a concentration at which no further solute will dissolve in a solution. At this point, the solution is said to be saturated. If additional solute is added to a saturated solution, it will not dissolve (except in certain circumstances, when supersaturation may occur). Instead, phase separation will occur, leading to either coexisting phases or a suspension. The point of saturation depends on many variables such as ambient temperature and the precise chemical nature of the solvent and solute.

Normality is the highlights the chemical nature of salts: in solution, salts dissociate into distinct reactive species (ions such as H+, Fe3+, or Cl-). Normality accounts for any discrepancy between the concentrations of the various ionic species in a solution. For example, in a salt such as MgCl2, there are two moles of Cl- for every mole of Mg2+, so the concentration of Cl- is said to be 2 N (read: "two normal"). Further examples are given below. Colour differentianting techniques is the quantitative study of color perception. It is similar to spectrophotometry, but may be distinguished by its interest in reducing spectra to tristimulus values, from which the perception of color derives. In this process there are several precaution to take over.For example, we need to prevent the parallal error due to using pipette and volumetric flask.

Conclusion. As the conclusion, the molarity of unknown solution can be done by doing colour differentianting. For that techniques we will easily determine the molarity and it normality.