CHM01 – Chemistry for Engineers – Laboratory
EXPERIMENT NO. 3
CONCENTRATION
INTRODUCTION
A solution may be classified whether dilute or concentrated. This is qualitatively
described based on the relative amount of solute against solvent. Quite differently, a
solution may be classified as unsaturated, saturated, or supersaturated. Their difference
lies on the concentration relative to the saturation value at a particular temperature.
There are several ways to express concentration. The simplest method is the
percent by mass and percent by volume in which the mass or volume of the solute is
divided by the total mass or total volume of the solution and multiplies by a hundred
percent. This is frequently used in laboratories not only in schools but also in some
industries. Molarity, which is the number of moles in a liter of the solution is equally
useful in pharmaceutical industry in particular and chemical industry in general.
Substances have different solubility in a particular solvent. Compounds which are
less soluble produce a dilute solution yet a saturated one. Conversely , a compound
may produce a concentrated and at the same time saturated if it has a relatively high
solubility.
OBJECTIVES
1. To understand how the concentration changes as more solute is being added.
2. To appreciate the concept of solubility and saturation in solutions.
PROCEDURE
1. Access this link as the simulator that will be used in this activity:
https://phet.colorado.edu/sims/html/concentration/latest/concentration_en.htm
l
2. Set the solvent at 0.5 L. Change the solute samples once you determined the
amount needed for the solution to be saturated. Use the concentration
detector to determine the required amount.
QUESTIONS
1. Know the saturation value of the substances used in the simulation. Which
one is the most soluble (in g/L)? Which has the highest molarity at its
saturation point? Encircle your answer in the table.
Solute
cobalt (II) nitrate
cobalt (II) chloride
potassium dichromate
potassium chromate
nickel (II) chloride
copper (II) sulfate
potassium permanganate
sodium chloride
Chemical Formula
Co(NO3)2
Saturation Value (g/L)
1031
CoCl2
562.2
K2Cr2O7
150.0
K₂CrO₄
650.5
NiCl₂
675.2
CuSO4
220.2
KMnO₄
75.9
NaCl
359.4
2. What is the solvent temperature used for this simulation? Refer to the
Solubility curve on the last page.
Solute
potassium dichromate
sodium chloride
Temperature ( °C)
28
30
APPLICATION PROBLEMS. Follow strictly the rules on Significant Figures.