Molarity Worksheet - CHEMISTRY



Calculating Molarity Practice: Show all your work including units. Box your final answer.

1. What is the definition and units of molarity?

2. Calculate the molarity of 0.060 moles NaHCO3 in 1500.0 mL of solution.

3. Calculate the number of moles of NaCl contained in 0.500L of a 1.5M solution.

4. Calculate the molarity of 34.2 grams of sugar, C12H22O11 in 500.0 mL of solution.

5. What is the molar concentration of 1.0 mol of KCl dissolved in 750.0 mL of solution?

6. Calculate the number of moles of NaOH contained in 250. mL of a 0.05M solution.

7. Calculate the molarity of 29.25 grams of NaCl in 2.0 liters of solution.

8. How many grams of NaCl are contained in the solution discussed in problem #3?

9. How many grams and moles of solute are there in 250. mL of a 0.10M CaCl2 solution?

Answers: 2) 0.040M (2sf) 3) 0.75mole (2sf) 4) 0.200M (3sf) 5) 1.3M (2sf) 6) 0.01mol (1sf) 7) 0.25M (2sf) 8) 44g (2sf)

9) 0.025mole and 2.8 g CaCl2 (2sf)

Making Solutions using Volumetric Flasks textbook pages 484

When making a solution, we use a piece of equipment called a volumetric flask. You make a solution by adding your solute first, dissolving it in a little bit of solvent, and then adding solvent until you get to the total volume line.

If you go over the line, you have to pour it out and start over because you have added too much solvent. This would make your Molarity higher / lower (circle one) than you needed, and your solution would be more dilute / concentrated (circle one) than you wanted.

Calculating how to make a solution: How would you make a 0.50 M NaCl solution using the volumetric flask to the left?

You have the Molarity from the problem and the volume in mL from the flask. You need to know how much solute, ___________, to add to the flask before you add the solvent, _____________.

Step 1: Convert the volume to Liters.

? L H2O =

Step 2: Use the Molarity formula to calculate how many moles of solute you need.

? mols NaCl =

Step 3: Convert the moles of solute to grams we can measure in a lab.

? g NaCl=

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250 mL

Lazy Scientist Note:

We abbreviate “the concentration of NaCl” as [NaCl].

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