| Procedural Tips
FAQs
Introduction/Goals
Background
Pre-lab
Additional Problems
Supplies and Chemicals
Safety Precautions
Waste Disposal Instructions
Chem 106 Lab Homepage
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In this lab, you will see the effect of solvent characteristics on the
solubility of common covalent and ionic compounds. In addition, the
solubility of NH4Cl will be
determined at various temperatures and a solubility curve constructed.
Finally, the concentration of a sodium chloride solution will be determined |
Print off a copy of the Grading Sheet
for this lab.
PROCEDURAL TIPS:
Using the Bunsen Burner
Using the Top-Loading Balance
FAQ:
Why do I have to wear safety goggles?
Are M and moles the same thing?
No, M is the abbreviation for molarity (molar concentration).
Molarity is the moles of a solute in 1 L of solution. The abbreviation
for the mole is mol.
INTRODUCTION/GOALS:
Introduction:
In this experiment, you will note the solubility of various
substances in polar and nonpolar solvents. Using the solubility rule -
like dissolves like- you will predict whether the solutes are polar or
nonpolar.
You will heat and cool a NH4Cl
solution and noting the temperature at which you first notice solid
crystals of NH4Cl . This is
the temperature at which the solution is saturated. You will
construct a solubility curve for NH4Cl using your data. Solubility is
defined as the number of grams of solute in 100 mL of solute.
You will be introduced to various ways of
expressing the concentration of a solution. You will determine the concentration (m/m%, m/v%, and M) of a sodium
chloride solution.
Goals:
 | Predict whether common substances are polar or nonpolar based on
their solubility in various solvents. |
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Determine the solubility of NH4Cl at various
temperatures. |
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Calculate the concentration of a solution in differing
concentration units (m/m%, m/v%, and M) |
BACKGROUND:
Soluble versus insoluble salts: Solubility is the
ability for a substance (a solute) to dissolve in a solvent. The solubility of a
substance depends on:
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the nature of the solute and the solvent: "Like
dissolves like" - nonpolar solutes are generally soluble in nonpolar
solvents, while polar solvents will dissolve polar solutes. A solute
will not dissolve in a solvent if the forces between solute particles
are too strong to be overcome by interactions with solvent particles,
or if solvent particles are more strong attracted to each other than
to solute particles. |
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the temperature: As the temperature increases, the
solubility increases. |
Concentration: The term concentration refers to the quantity of
solute in a quantity of solution. There are several ways of expressing
the concentration of solutions:
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Molar concentration or molarity (M) is defined
as the number of moles of solute in 1 liter of solution. |
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Percent solutions are defined as the parts of
the solute in the solution expressed as a percentage. 2 types of
percent solutions are common:
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mass/volume percent (m/v): grams of solute/100
milliliters of solution |
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mass/mass percent (m/m): grams of solute/100 grams of
solution |
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PRE-LAB:
Read the introductory material on the webpage.
Read Experiment Eleven in the laboratory manual.
Answer the pre-lab study questions for Experiment
Eleven.
You are encouraged to do the Application Questions at
the end of Experiment Eleven before coming to lab.
ADDITIONAL PROBLEMS:
- How many grams of sodium chloride are required to prepare 500 mL of
a 7.5% (m/v) NaCl solution?
- The solubility of NaOH is 109 g per 100 g of water at 20 ºC. What is
the (m/m)% concentration of a saturated NaOH solution at 20 ºC?
- What volume of 0.0250 M NaOH is needed to give 8.10 g of NaOH?
- Would you expect the following compounds to be soluble or insoluble
in water? in toluene?
- NaI
- CH4
- Mg(NO3)2
- CO2
- Which of the following solutions, 1% (m/m) or 1 mg/dL, is most
concentrated?
- Answer 9.63 in your McMurrary textbook.
SUPPLIES AND CHEMICALS
SAFETY PRECAUTIONS:
SAFETY GOGGLES MUST BE WORN AT ALL TIMES DURING
THE LAB.
WASTE DISPOSAL INSTRUCTIONS:
Liquid waste for part A should be disposed of in the
waste container found under the hood. The container should be labeled
"Organic Waste-Experiment 11.
Dispose of NH4Cl
solutions in
the appropriately labeled container found under the hood. Do not
throw NH4Cl
solutions down the sink.
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