CHE 122 GMC Concentration Temperature and solubility of Salts Lab Report CHE-122: Principles of Chemistry II Laboratory 1 Procedure – Concentration, Tempe

CHE 122 GMC Concentration Temperature and solubility of Salts Lab Report CHE-122: Principles of Chemistry II

Laboratory 1 Procedure – Concentration, Temperature and the Solubility of Salts

Background:

Solution is a homogeneous mixture of solute and solvent, solution = solute + solvent.

Figure 1. Ionic compound, NaCl salt (solute), dissolved in water (solvent) forming the solution.

In this experiment we will analyze water solutions of ionic compounds, their concentration, and solubility in water.

Concentration, in our case molar concentration, is the amount of solute, expressed in moles, that is divided by volume of the solution, expressed in liters. In the formula bellow, M is a molar concentration, n is a number of moles, and V is a volume of a solution.

M = n/V

Equation 1. Molar Concentration.

Solubility provides information about amount of solute that can be completely dissolved in solvent at given temperature. It is expressed in grams of solute per 100 grams of solvent.

Figure 2 shows the typical representation of the solubility data, that is combined in the plot called temperature and solubility curve.

Figure 2: Temperature and Solubility Curve for Various Ionic Compounds in Water.

This plot can tell us the mass of salt, expressed in grams, that can be dissolved in 100 grams of water at given temperature. There are three types of solutions that are described in this graph:

Unsaturated solution: The solution that does not contain maximum amount of salt that can be dissolved in 100 g of water at given temperature (all the values below the graph line for analyzed salt).

Saturated solution: The solution that contains maximum amount of salt that can be dissolved in 100g of water at given temperature (the values on the graph line for the analyzed salt).

Supersaturated solution: The solution that contains excess of the dissolved salt than could be dissolved by the 100g of water under normal circumstances, temperature, and/or pressure (points above the curve for the analyzed salt).

Temperature and solubility of ionic compounds: Temperature allows to dissolve more solute in 100 g of water, so we say that in most cases solubility of the ionic compounds increases with temperature.

There are several objectives of this lab:

To enhance your ability to perform molar concentration to mass of the solute calculations.
To familiarize you with the solubility curve
To improve your comprehension of the solubility.
Pre-Lab Questions:

Analyze Figure 2. Temperature and solubility curve for potassium nitrate, KNO3,

And answer the following questions:

What property is listed on x-axis?
What property is listed on y-axis?

2.Using graph for KNO3, in Figure 1, decide if the following solutions would be saturated or unsaturated?

110g of sodium nitrate in 100g of water at 40°C?
60g of sodium nitrate in 100g of water at 70°C?

a. 140g of sodium nitrate in 200g of water at 60°C?

3.According to the graph in Figure 1, will 50g of sodium nitrate completely dissolve in 100g of water at 50°C? Explain.

Procedure:

Collecting Data

From the course home page, access the simulation environment by clicking on the Concentration

link.

1.After the simulation environment loads, set Volume for 0.1L by clicking on the bottom faucet. If necessary, you can add water by clicking on the top faucet.

Select cobalt (II) nitrate, Co(NO3)2, from the “Solute” category.
Gently shake saltshaker to add salt (solute) to the solvent.
Keep adding until you obtain saturated solution.
Record the concentration of cobalt (II) nitrate.
Use Molar Concentration, M, to obtain number of moles, n, and then convert n to mass of the salt, m.
Remember that the volume equals 100 mL (we can assume that the density of water is 1 g/mL so 1mL = 1g).
Use n = m/MM for mass calculation, n is a number of moles, m is mass in grams, MM is molar mass in g/mol, calculated from atomic masses listed in periodic table.
Record your calculations:
Analyze your data and compare it with Figure 2. a solubility curves.
Record your observations.
Prepare complete lab report.

Repeat procedure described in points 3-6 for two more salts: potassium permanganate, KMnO4, and sodium chloride, NaCl.

Solute/Salt

Solution Concentration in mol/L

Solution Volume in L

Co(NO3)2

KMnO4

NaCl

Calculations and Data Analysis

6.Using solution concentration data collected in Point 7 calculate amount of salt in grams that dissolved in 100 g water.

Solute/Salt

M in mol/L

n in mol

MM in g/mol

m in g

Solubility in g/100g of water

Co(NO3)2

KMnO4

NaCl

Notes

This section should include notes about any observations or calculations of data collected during the lab.

Preparing Solubility Curve

13.Using the following data draw the solubility graph for cobalt (II) nitrate, graph has to be included in the labreport:

Temperature, °C

0

18

91

Solubility, g/100g of water

84.03 g

98.93

338.9

14.Use your solubility curve to obtain the temperature of your simulation. Hint: use solubility of Co(NO3)2 calculated in point 11.

Report Requirements
This section contains key information that must be included in your typed report.

1.Define the problem in a manner that is clear and insightful.

Identify the strategies and procedures used during the lab.
Clear presentation of data including any tables or other figures that are relevant to understanding your stated conclusions at the end of the report. Include any relevant calculations performed during the lab.
Clearly stated results and discussion of possible improvements to the procedure.
Conclusive statements arguing in favor of your findings.

2.Clear hypothesis statement and other potential solutions that identify any relevant contextual factors (i.e. real-world costs).

Note: All reports will be graded using the rubric embedded within the course.

Here are some questions to consider as you write your report:

Does my problem statement make sense?

Have I summarized my strategies/procedures well enough to be replicated by an outsider?
Did I have a valid hypothesis at the start of the lab? Have I expressed this in my report?
Do my tables and/or graphs make sense?
Are my conclusions valid based on my supplied data?
Did I thoroughly summarize my laboratory experience in a concise, factual way such that the reader can understand my processes and findings in the conclusion section alone?