Lab Molarity

Welcome to your "sort of" first online lab. I would like to use this first lab activity to cover some additional lecture material and then follow it up with a short activity.

Section 4.5: Concentration of Solutions

You may have noticed in lab that many of the solutions we used had a label like "3M" to indicate the concentration of the solute in the solution. 3M means 3 molar or the molarity is 3. As you will see in your text the definition of molarity (M) is the moles of solute divided by liters of solution.

Example 1

What is the molarity of a solution made by adding 1.23 moles of sodium chloride to 1 .00 L of water?

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Answer: 1.23 M NaCl

Example 2

What is the molarity of a solution made by adding 12.34 grams of sodium chloride to 1.000 L of water? (Note: you will need to calculate the molecular mass of NaCl...)

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molecular mass of NaCl...

12.34 g of NaCl = ? moles of NaCl

then calculate M = ?

Answer: 0.2112 M NaCl

Hard (but not really) Example

What is the molarity of a solution made by adding 43.21 grams of sodium chloride to 1,234 mL of water?

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Answer: 0.5992 M NaCl