What is a solution?
A Solutions is a homogeneous mixture in which one substance is dissolved in another. A solution includes both a Solute and a Solvent.
- Solute: the substance that is being dissolved
- Solvent: the substance that is doing the dissolving, sometimes the largest amount of substance there (water is a universal solvent).
Salt water is a simple example of a solution, which one would be the solute and which would be the solvent?
- Salt would be the solute because it's the substance that is being dissolved.
- Water would be the solvent because it's the substance that is doing the dissolving.
what is Solubility?
Solubility is the amount of a substance that dissolves in a given volume of solvent or solution at a given temperature.
There are 3 factors that affect the rate of solubility (how fast a substance dissolves).
Here are a few rules that you must remember (when it comes to the rate of solubility with temperature and pressure):
(Only gases are affected by pressure)
There are 3 factors that affect the rate of solubility (how fast a substance dissolves).
- Increasing the temperature
- Size of the particles (smaller particles dissolve faster)
- Stirring the solution
Here are a few rules that you must remember (when it comes to the rate of solubility with temperature and pressure):
- Solids become more soluble as the temperature increases
- Gases become less soluble as the temperature increases
- Pressure has no effect on solids and liquids
- Gases become more soluble as the pressure increases
(Only gases are affected by pressure)
Molarity and Molality
Molarity represents the number of moles of solute per liter of solution.
Let's start with an example:
1. What is the molarity of 2.5 L of solution that contains 1.0 mol MgCl2?
This is a simple problem, you just pop the information into the formula!
M= 1.0 mol/2.5 L = 0.40 Molarity or just M
2. How many moles of solute are present in 400 mL of 2.0 M KNO3?
Here we have to change the mL to L and find the moles, to change the mL to L, put the number over 1000
(1000 mL = 1L)
400mL/1000 = .400L
Now put the information into the formula!
2.0 M= x mol
.400 L (Now you can cross multiply and divide)
= 0.8 mol
3. How many grams of CaCl2 are in 350 mL of 2.0 M CaCl2 solution?
With this one, we will also need the formula for grams which is g= molar mass x mol
Ca = 40.078 + Cl2 = 35.453(2) = 110.984
Don't forget to change the mL to L
2.0 M= x mol
.350
= 7.8 g
Molality represents the number of moles and solute per kilogram of solvent
Let's try a sample problem!
1. Calculate the molality of a solution that has 1.5 moles added to 675 mL of solvent
675 mL/1000 = .675 L
1.5 mol/.675 mL = 2.2
Dilution is the addition of water to a concentrated solution
For these, all you have to do is plug everything into the equation!
1. If you had 40.0 mL of a 3.00 M hydrochloric acid solution and you wanted to dilute it to 2.00 M, what would be the new volume?
M1 = 3.00 M
V1 = 40.0 mL
M2 = 2.00 M
V2 = ?
120 M = 2.00 M
2 mL 2mL
Cross multiply and divide!
= 60 mL
Now here's another problem for you to try!
2. If you dilute 70.0 mL of 5.0 M NaCl to make a 350.0 mL of solution, what is the molarity of the dilute solution?
M1 = 5.0 M
V1 = 70 mL
M2 = ?
V2 = 350 mL
= 1.2 M
- Molarity (M) = Moles of solute/liters solution
Let's start with an example:
1. What is the molarity of 2.5 L of solution that contains 1.0 mol MgCl2?
This is a simple problem, you just pop the information into the formula!
M= 1.0 mol/2.5 L = 0.40 Molarity or just M
2. How many moles of solute are present in 400 mL of 2.0 M KNO3?
Here we have to change the mL to L and find the moles, to change the mL to L, put the number over 1000
(1000 mL = 1L)
400mL/1000 = .400L
Now put the information into the formula!
2.0 M= x mol
.400 L (Now you can cross multiply and divide)
= 0.8 mol
3. How many grams of CaCl2 are in 350 mL of 2.0 M CaCl2 solution?
With this one, we will also need the formula for grams which is g= molar mass x mol
Ca = 40.078 + Cl2 = 35.453(2) = 110.984
Don't forget to change the mL to L
2.0 M= x mol
.350
= 7.8 g
Molality represents the number of moles and solute per kilogram of solvent
- Molality = moles of solute/kilograms of solvent
Let's try a sample problem!
1. Calculate the molality of a solution that has 1.5 moles added to 675 mL of solvent
675 mL/1000 = .675 L
1.5 mol/.675 mL = 2.2
Dilution is the addition of water to a concentrated solution
- M1V1 = M2V2
For these, all you have to do is plug everything into the equation!
1. If you had 40.0 mL of a 3.00 M hydrochloric acid solution and you wanted to dilute it to 2.00 M, what would be the new volume?
M1 = 3.00 M
V1 = 40.0 mL
M2 = 2.00 M
V2 = ?
120 M = 2.00 M
2 mL 2mL
Cross multiply and divide!
= 60 mL
Now here's another problem for you to try!
2. If you dilute 70.0 mL of 5.0 M NaCl to make a 350.0 mL of solution, what is the molarity of the dilute solution?
M1 = 5.0 M
V1 = 70 mL
M2 = ?
V2 = 350 mL
= 1.2 M
solubility chart
First, here is a solubility rules chart!
solubility graph
Solubility Curves show the amount (g of solute/100 g of H2O) of a substance that dissolves in a given volume of solvent or solution at a given temperature (Celsius)
1. How much KNO3 will dissolve in 50 mL of water that is at 30 °C? 45g
2. If you stir 20 grams of KNO3 in 100 mL of water that is at 50°C, will all of it dissolve? Yes
3. A solution that contains 120 grams of MgSO4 in 100 mL of water at 80°C would be saturated, unsaturated, or supersaturated? Supersaturated
1. How much KNO3 will dissolve in 50 mL of water that is at 30 °C? 45g
2. If you stir 20 grams of KNO3 in 100 mL of water that is at 50°C, will all of it dissolve? Yes
3. A solution that contains 120 grams of MgSO4 in 100 mL of water at 80°C would be saturated, unsaturated, or supersaturated? Supersaturated
- Saturated - point is on the curve of the line
- Unsaturated - point is below the curve at a given temperature
- Supersaturated - point is above the curve at a given temperature