Chap11 -Exercises Flashcards
Concentration Problem
250 g of sugar is dissolved in enough water to make 2.5 L of solution. What is the concentration of this solution?
10% m/V
A 500 mL saline solution is made by dissolving 10 g of salt.
a)What is the concentration of the saline solution in g/L?
b)What is the concentration of
the saline solution in %(m/V)?
a)20g/L
b) 2% (m/V)
Concentration Problem
Gargling with a salt solution can help with sore throats. The recommended recipe for a salt solution is to dissolve 3 g of salt in 240 mL of water. Calculate the recommended concentration in:
a) g/L
b) %m/V
a) 12.5 g/L
b)1.25%(m/V)
Concentration Problem
How much antibiotic is needed for a pharmacist to make 300 mL of a 0.5 %(m/V) antibiotic solution?
1.5g of antibiotic is needed
How is the particle model useful and what are the limitations of the particle model?
The model helps usunderstand how the particles are organized as well as how they behave. It allows us to make predictions based on this model.
The model is limited as it is a simplified version of reality (e.g., in the case of water the particles are further apart in the solid phase than in the liquid phase).
Which of the following results in a dilution of a solution?
A) Evaporating some solvent
B) Adding more solvent
C) Adding more solute
D) Removing solute
B
Which of the following examples describe a dilution? (hint: there could be more than one)
A) Add more sugar to iced tea.
B) Add water to cool down hot chocolate.
C) Putting powdered milk in water and stirring.
D) Add 3 cups of water to orange juice from concentrate.
A and D
A lab technician receives 1 L of a concentrated solution. He will need a solution with half the concentration. What should he do?
A) Add 500 mL of solvent.
B) Add 500 mL of solute.
C) Add 1 L of solvent.
D) Add 1 L of solute.
C
Dilution problems
A lab technician has 500 mL of a hydrochloric acid with a concentration of 36 g/L. She
dilutes the solution to a final volume of 1.2 L. What is the concentration of the dilute
solution?
15 g/L
What volume of a 200 g/L concentrated salt solution is needed to make a 3 L solution at a concentration of 40 g/L?
A) 0.6 L
B) 1.67 L
C) 15 L
D) 2667L
A
In the lab, you are given 50 mL of a 5 g/L solution of sugar and water. You want to dilute the solution to make a solution with a concentration of 2 g/L. Calculate the amount of water you have to add to the original solution.
75 mL needs to be added to achieve the final volume
You place a pot of water on the stove to boil in order to make some tea. Draw the particle model of the phases of the water as it heats.
Possible answer:
An unknown liquid needs to be tested to see if it’s an acid, a base or if it is neutral. There is no more pH paper and all that is left is red litmus paper. The following result is obtained:
- The red litmus paper stays red
Which of the following conclusions must be true?
A) It is a base
B) It is an acid
C) It is neutral
D) It is not a base
The answer is D: It is not a base.
Why?
When using red litmus paper, if it stays red the substance being tested could be either an acid or neutral
Here is a reminder of how to decode result using Blue and Red litmus paper:
* Red stays red and blue turns red = acid
* Blue stays blue and red turns blue = base
* Red stays red and blue stays blue = neutral
Saline solutions have many health applications. These solutions are made by dissolving salt in water. Which of the following statements (plural!) are true for a saline
solution?
1) Salt is the solute.
2) Salt is the solvent.
3) Water is the solvent.
4) Water is the solute.
5) Saline solutions are heterogeneous mixtures.
6) Saline solutions are homogeneous mixtures.
Answer: 1, 3 and 6
