Preparing Solutions

LG: I can use formulas for concentration to prepare standard solutions from a solid

Practice Calculation• What mass of solid sodium hydroxide would

be required to prepare 100 mL of 0.500 mol/L solution?

Standard Solutions• Solutions with precisely known concentrations

are called standard solutions.– Measurements are only as accurate as your

equipment!

• Standard solutions can be prepared by dissolving a solid solute in a solvent, OR

• By diluting a more concentrated solution

Activity 1: Preparing a Standard Solution from a Solid• Calculate the mass of solid required to prepare specified

volume of solution• Measure the required mass in a clean, dry, 50 mL beaker• Dissolve the solid in ~40 mL of pure water• Transfer the solution to a volumetric flask (100 or 250 mL)• Rinse the beaker 2 or 3 times with small amounts of pure

water and add the rinsings to the flask• Add pure water to the flask until the volume is 100.0 mL• Stopper the flask and seal with Parafilm, then mix by

inverting repeatedly

Preparing Solutions

LG: I can use formulas for concentration to prepare standard solutions by dilution

Practice Calculation

• You need 100 mL of 0.200 mol/L hydrochloric acid. The only solution available is 1.5 mol/L. What volume of the more concentrated acid will you require?

Activity 2: Preparing a Standard Solution by Dilution• Calculate the volume of 0.500 mol/L standard solution

required to prepare 100 mL of 0.100 mol/L solution.• Add 40-50 mL of pure water to a 100 mL volumetric

flask.• Measure the required volume of standard solution using

a 10 mL pipet and transfer to the 100 mL flask• Add pure water until the final volume is reached• Stopper the flask and mix thoroughly by inverting