Show:
Homogeneous/
heterogeneous systems
Mixtures
Solutions
Concentration of a solution
Solubility
100
Is gold a homogeneous system or a heterogeneous system? Justify your answer.
It is a homogeneous system because it has a uniform appearance.
100
Give an example of a heterogeneous mixture.
Open answer
100
What is a solution?
A solution is a homogeneous mixture made of two or more components.
100
What is the concentration of a solution which has been prepared by dissolving 30 g of a solute in 2 L of water?
15 g/L
100
The solubility of a solute in water at 20 ºC is 56 g of solute/100 g of water. Decide if the following solutions are dilute, concentrated or saturated: Solution A: 46 g of solute/100 g of water. Solution B: 56 g of solute/100 g of water. Soltuion C: 3 g of solute/100 g of water.
Solution A: Concentrated. Solution B: Saturated. Solution C: Dilute.
200
Is a mixture of sugar and water a homogeneous system or a heterogeneous system? Justify your answer.
It is a homogeneous system because it has a uniform appearance.
200
Give an example of a homogeneous mixture
Open answer
200
What is the solute?
The solute is the component of a solution which is in a lower proportion.
200
Calculate the concentration of a solution which has been prepared by dissolving 12 g of salt in water. The volume of the solution is 300 mL
40 g/L
200
The solubility of salt in water at 20 ºC is 36 g of salt/100 g of water. Give an example of a concentrated solution.
Open answer
300
Is a mixture of chalk and chalk powder a homogeneous system or a heterogeneous system? Justify your answer.
It is a heterogeneous system because it has a non-uniform appearance.
300
True or false: Heterogeneous mixtures have the same properties in all their points. Justify your answer.
False. They have different properties in different points of the mixture. For example a salad does not have the same color in all its points.
300
Decide which is the solvent and which is the solute in the following solution: 5 g of sugar are dissolved in 1.5 L of water.
Solute: sugar. Solvent: Water.
300
What is the formula to calculate the concentration of a solution?
Concentration = mass of solute (g)/volume of solution (L)
300
The solubility of sugar in water at 20 º C is 204 g of sugar/100 g of water. Give an example of a dilute solution.
Open answer
400
What is a homogeneous system?
It is a material system which has a uniform apperance. It can be made of one or several substances.
400
Is a soft drink a homogenous mixture or a heterogeneous mixture? Justify your answer
It is a heterogeneous mixture (we can see the bubbles of carbon dioxide).
400
Give an example of a solid solution.
Open answer. Milk chocolate (chocolate and milk) Steel (iron and carbon) Bronze (copper and tin) Brass (copper and zinc)
400
Definition of concentration.
It is the amount of a solute which is dissolved in a specific amount of solution.
400
The solubility of salt in water at 20 ºC is 36 g of salt/100 g of water. What happens if we add 50 g of salt to 100 g of water.
36 g of salt dissolve and 14 g of salt precipitate.
500
True or false: Heterogeneous systems are always made of two or more substances. Justify your answer
False. A heterogeneous system can be made of only one substance in different states. Eg. water and ice.
500
Which are the main differences between homogeneous and heterogeneous mixtures?
1. The components of a homogeneous mixture cannot be distinguished while the components of a heterogeneous mixture can be distinguished. 2. Homogeneous mixtures have the same composition and properties in all their points while the composition and properties of a heterogeneous mixture are different in different points of the mixture.
500
Explain how to prepare 500 mL of a solution made of 20 g of sugar and water.
1. Measure 10 g of sugar with a balance. 2. Pour the sugar in a beaker and add water (less than 500 mL). Stir until the sugar is dissolved. 3. Pour the solution in a 500 mL volumetric flask and add water until you are near the line marked on the flask. 4. Use a dropper to fill the volumetric flask. Use the meniscus of the water and the line on the flask to determine your endpoint.
500
Decide which of the following solutions have a higher concentration: Solution A has been prepared by dissolving 25 g of sugar in water. The volume of the solution is 500 mL. Solution B has been prepared by dissolving 50 g of sugar in water. The volume of the solution is 750 mL.
Solution B has a higher concentration. Concentration of solution A: 50 g/L. Concentration of solution B: 66,67 g/L.
500
What is solubility?
Solubility is the maximum amount of a solute which can be dissolved in a solvent at a certain temperature.