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.

Easy Example

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

Medium Example

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