Ch. 4 - Chemical Reactions

Molarity and Dilution Homework

Molarity Calculations

Determine the molarity of the following solutions.

1. 0.45 moles of sodium chloride is dissolved to make 1.00 L of solution.

2. 0.5 moles of sodium chloride is dissolved to make 0.05 liters of solution.

3. 0.5 grams of sodium chloride is dissolved to make 0.050 liters of solution.

4. 0.5 grams of sodium chloride is dissolved to make 0.050 mL of solution.

5. 734 grams of lithium sulfate are dissolved to make 2500 mL of solution.

6. 6.7 x 10^-2 grams of Pb(C₂H₃O₂)₄ are dissolved to make 3.5 mL of solution. (Ensure that your answer is in standard form).

7. Name 2 instruments that are commonly used to measure volume. (Note: beaker is not a valid answer).

8. Are the same volumetric instruments being used in numbers 2 and 3? Why or why not? (Use complete sentences when responding).

Dilution Calculations

Solve the following problems.

1. 25 mL of water are added to 125 mL of a 0.15 M NaOH solution. Determine its molarity.

2. A chemist begins with 100. mL of a 0.15 M solution.

a. If water is added until the final volume is 150. mL, what is the molarity of the new solution?

b. Is this a dilution or reduction? Why?

3. How much 0.050 molar hydrochloric acid solution can be made by dilution 250 mL of 10.0 molar hydrochloric acid?

4. A chemist has 345 mL of 1.5 M NaCl (aq). The water is boiled until the volume of the solution is 250. mL.

a. Determine the molarity of the solution.

b. Is this a dilution or reduction? Why?

5. A chemistry lab group has 500. mL of 2.4 M waste residue. The molarity of the waste residue needs to be reduced to 1.0 M before it can safely be introduced to the environment. How much water (minimum) needs to be added to the waste?

6. 50 mL of a solution of lithium oxide has a molarity of 3.0 M. How many grams of the solute are present?

Titration Simulation

https://pages.uoregon.edu/tgreenbo/acid_base.html

*Group work permitted.

*Document your work on each (numbered) step so that another person can duplicate your entries.

*Use phenolphthalein (#4) as an indicator.

*This is a guaranteed collection.