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Chemistry Stoody Guide

Molarity

  1. Perform conversions involving molarity
  2. Write the steps of a procedure to make a solution of a specific and precise concentration from a solid sample or a stock solution of known concentration

Molarity

Molarity: Measure of the concentration of a solute in a solution. It is defined as the number of moles of solute per liter of solution. For example, if a solution contains 1 mole of NaCl in 1 liter of water, the molarity of the solution is 1 M. If 1 mole of NaCl is dissolved in 2 liters of water, the molarity is 0.5 M.

To solve molarity problems, set up dimensional analysis. For example, if a 45.3 g sample of NaCl is dissolved in 1.5 L of water, the molarity of the solution is:

Making a Solution of a Specific Concentration

Given a type of element, and a desired molarity, the steps to make a solution of a specific concentration are essentially the steps to calculate molarity given a mass and volume of solution, but in reverse. For example, to make a 250 ml and 0.5 M solution of NaCl: