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Lesson Instructions
Lesson Instructions
Review the learning goals and success criteria for Topic 4: Solutions.
Review the minds on, action, and consolidation sections of the lesson, completing any tasks as outlined.
Complete the fill-in-the-blanks handouts that have been provided to you. They have been linked below.
Practice and apply what you've learned by completing the practice tasks outlined at the end of the lesson.
Learning Goals
Learning Goals
I am learning to ...
Describe molar concentration.
Perform calculations using molar concentrations.
Success Criteria
Success Criteria
I am able to ...
Describe molar concentration.
Use molar concentration to perform calculations.
Describe the term “dilution” and perform simple calculations.
Minds-On
Minds-On
The Breathalyzer
The Breathalyzer
Solution chemistry is an important concept to understand when thinking about how a Breathalyzer works. The breathalyzers that were first developed relied on a chemical reaction that was able to quantify the amount of alcohol in someone's blood based on the strength of the colour produced in a sample. The indicator fluid, which changed from yellow to green in the presence of alcohol. The person using this early device exhaled through a straw immersed in the liquid sample, allowing alcohol in their breath to enter the liquid. A beam of light was passed through this sample, and a detector recorded the change in colour intensity.
Figure 1. A police office is testing a persons blood alcohol content levels using a breathalyzer.
Testing Water Samples
Testing Water Samples
Tap water is quantitatively analyzed regularly across different cities and regions. It is important to maintain healthy, drinkable levels of different solutes. There are many different elements found in our drinking water. For example, the standard level for chlorine in our tap water is 250 mg/L – that is, 250 mg of chlorine for every 1L of water. Sometimes these concentrations are expressed as PPM which stands for parts per million. If chlorine levels were to rise significantly above 250 mg/L, your tap water would start to taste like swimming pool water. Yuck! Municipalities are responsible for routinely measuring the amount of chlorine contained in tap water and making sure it safe for consumption.
Figure 2. Chlorine levels in our tap water are routinely monitored by the municipalities in which we reside. The standard level for chlorine in our tap water is around 250 mg/L.
Action
Action
Concentration of Solutions
Concentration of Solutions
The molar concentration (C) of a solution is defined as the number of moles of solute dissolved per liter of solution.
The units of molar concentration (C) is written as mol/L.
Figure 3. Mole triangle to help us with calculations involving concentration of solutions.
Think back to when we learned about homogenous mixtures. Remember that matter exists in various phases, such as solid, liquid, or gas. Mixtures are said to be homogeneous if they have only one visible phase, so when you look at the mixture you see only one ‘layer’. If a homogenous mixture is in the liquid and gaseous state, this mixture is also called a solution. Tea, coffee, powdered drink, salt water, non-pulp orange juice, and the air we breathe are all examples of homogeneous solutions. The other type of solution is referred to as a heterogeneous mixtures. These mixtures have more than one visible layer or phase. Oil and vinegar salad dressing, dusty air, beach sand, topsoil, and orange juice with pulp are examples of heterogeneous solutions.
What is a solution?
What is a solution?
Solutions are made up of two main parts – the solute and the solvent.
The solute is the substance dissolved in another substance called the solvent.
The solute and the solvent can be solid, liquid, or gas.
In this example of a tea ...
The tea/water/liquid is the solvent.
The sugar being added is the solute.
Both the solute and the solvent form a solution of sweetended tea.
Figure 4. Diagram highlighting the difference between a solute, solvent, and a solution.
Examples of Solutions
Examples of Solutions
Mixing gatorade drink powder in water.
Water is the solvent, the drink powder is the solute.
150 g of magnesium sulphate is dissolved in 300 mL of water.
Water is the solvent; the magnesium sulphate is the solute.
Figure 5. Gatorade drink powder.
Figure 6. Solution of magnesium sulfate for medicinal use.
Calculations Involving Concentration of Solutions
Calculations Involving Concentration of Solutions
Example 1.
Example 1.
A saline solution contains 0.90 g of sodium chloride, NaCl, dissolved in 100 mL of solution. What is the molar concentration of the solution?
Example 2.
Example 2.
Calculate the mass of solute needed to make 250 mL of a 0.50 mol/L solution of NH4Cl.
Example 3.
Example 3.
How many molecules of KNO3 are in 210 mL a 0.30 mol/L solution?
Preparing Solutions & Dilutions
Preparing Solutions & Dilutions
There are two different ways that we can prepare a solution.
Method 1
Method 1
Weigh out a solid, and add water to dissolve it.
Method 2
Method 2
Using an aqueous stock solution and add water to dilute it
Calculations for Preparing a Solution
Calculations for Preparing a Solution
Example 4.
Example 4.
For a class experiment, Mr. Coleiro must make 250 mL of 0.10 mol/L copper (II) sulfate solution. How would Mr. Coleiro prepare this solution?
Calculations for Diluting a Solution
Calculations for Diluting a Solution
Figure 7. Formula use when performing a dilution.
You can dilute a solution by adding more solvent. Think about making orange juice from frozen concentrate. The formula that we use when dealing with dilution calculations is C1V1=C2V2. Think about when we discussed Gatorade. Imagine you added too much gatorade powder. You could dilute the solution of gatorade by adding water to decrease the concentration of the drink powder.
Example 5.
Example 5.
How would you prepare 100 mL of a 0.20 mol/L solution of HCl from a stock solution with a concentration of 1.0 mol/L?
Applications of Solution Calculations
Applications of Solution Calculations
Example 6.
Example 6.
A zinc chloride solution can be used to make fingerprints more visible to forensics experts. What mass of zinc chloride is needed to make 1.0 L of a 0.020 mol/L solution?
Figure 8. Detecting Fingerprints on stone and other difficult porous surfaces via zinc chloride and a laser.
Example 7.
Example 7.
A pharmacist takes 150 mL of 0.100 mol/L solution of folic acid and dilutes it by adding 350 mL of water. What would the concentration of the new solution be?
Figure 9. A Pharmacist carrying out a dilution in their lab.
This lesson is now complete. Return to D2L - Brightspace and complete the assigned tasks to consolidate your learning.
On D2L you will complete the following task.
Topic 4 Practice Assignment: Solutions (Hand-in for evaluation)
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