Preparing Solutions

• Solutions are commonly prepared by– Using solid solute– Diluting a concentrated solution

• When preparing a solution from solid solute, first use the molarity equation determine the mass of the solute required.

Preparing a Solution from Solid Solute

• An experiment calls for 250 mL of a 0.10 M NaCl solution. How many grams of solid NaCl are required to make the solution? Explain how you would create this solution.

Steps Involved in Preparing Solutions from Solids

– Calculate the amount of solid required– Mass out the solid– Place in an appropriate volumetric flask– Fill flask about half full with water and mix.– Fill to the mark with water and invert to mix.

Steps Involved in Preparing Solutions from Solids

What Do You Think?

• A chemist wants to make 100.0 mL of a 4.0 M sodium hydroxide (NaOH) solution. What mass of NaOH is required to make the solution?

Preparing Solutions from Other Solutions

• Many times solutions are prepared by diluting concentrated solutions. These are called stock solutions.

• Dilution = process of adding water to a stock solution to achieve the molarity desired for a particular solution.

• Adding water increases the volume of the solution and this causes the concentration to decease.

• Dilution Equation:

M1V1 = M2V2

Preparing a Solution by Dilution

• An experiment calls for 500 mL of a 0.10 M HCl solution. How many milliliters of 12 M HCl are required for the dilution? Explain how you prepare the solution.

Dilution• Make a diluted solution once you know V1 and V2

– Use a pipet/graduated cylinder to deliver a volume of the concentrated solution to a new volumetric flask.

– Add solvent to the line on the neck of the new flask.

– Mix well.

Its Your Turn1. How many mL of 5.0 M K2Cr2O7 solution

must be diluted to prepare 250 mL of 0.20 M solution?

2. If 10.0 mL of a 10.0 M stock solution of NaOH is diluted to 250 mL, what is the concentration of the resulting solution?

Wrapping It Up• Reflect on what you have learned concerning the today’s

topic.

• Respond to the following…– What is the most important thing you learned today?– What is one question you would still like answered?– What is a way what you have learned today connects with

what you knew before?