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LAB REPORT
DILUTION
Group Members
Ali
Rajeh
OBJECTIVE
The objective of the experiment is to prepare two solutions:
a. sodium chloride solution
b. dye solution
The sodium chloride solution is then evaporated and the mass of sodium chloride is measured.
The dye solution is prepared and its absorption spectrum is obtained.
THEORY
Sodium chloride (NaCl) is an ionic compound of positive sodium ions and negative chloride ions.
When positive molecules of water attract negative chloride ions and when negative water molecules
attract positive sodium ions, water dissolves sodium chloride in it. When such a solution is formed,
sodium chloride is called the solute and water is the solvent. To such a solution, when more solvent is
added to decrease the concentration, the process is called dilution. The number of moles of a solute per
litre of solution is called as molarity or molar concentration, M, of the solute.
𝑀𝑜𝑙𝑎𝑟𝑖𝑡𝑦, 𝑀 =
𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠, 𝑛
𝑉𝑜𝑙𝑢𝑚𝑒 𝑖𝑛 𝑙𝑖𝑡𝑟𝑒𝑠, 𝑉
When this NaCl solution is evaporated, water in the solution evaporates and we obtain the solute, NaCl.
If dilution is proper, the molarity of concentrated solution will be equal to the molarity of diluted
solution.
When dye solution is diluted, absorption spectrum of the dye solution is obtained using a
spectrophotometer. Absorbance is the amount of light blocked by the molecules of a solution. From the
absorption spectrum, molarity of the diluted dye solution is calculated. If dilution is proper, according to
Beer Lambert’s law, the Absorbance Vs Concentration graph will be linear.
PROCEDURE
Dilution of NaCl solution
1. Number of moles of NaCl required to prepare 250mL of 1.5M NaCl solution was calculated as
per below given formula.
250 mL ×
1.5𝑀
1𝐿
= 0.375 mol of NaCl
2. 1 mol of NaCl weighs 58.43g or molar mass of NaCl = 58.43g. Thus, Mass of NaCl required is then
calculated as follows:
0.375moles × 58.43 g/ moles = 21.99 g
3. Take exactly 21.91g of NaCl for the experiment using a weighing machine, record it and
carefully transfer it to a 250mL volumetric flask.
4. Add water to it and stir well to dissolve NaCl in the water completely.
5. Add more water to make up 250mL of the solution. Be careful to add water drop by drop when
the level of water is near the 250mL mark in the neck of the volumetric flask so that the level of
water doesn’t exceed the 250mL mark.
6. The actual concentration of this ...