Chem1: Lecture Week 6 Discussion: Solutions and Concentration Lecture Discussion

At home and at work, chemistry is all around us. The names of chemicals and units used to describe their concentrations are often different when we encounter them in our everyday lives, though. For example, we can buy distilled white vinegar at the supermarket for cooking and cleaning, but the same solution could be found in a chemistry lab labelled as 5% (w/w) acetic acid or 0.833 M acetic acid.

Some other common solutions and their typical concentrations include:

Beer, 4-8% ethanol (v/v)
Rubbing alcohol, 70-99% isopropanol (v/v)
IV Dextrose, 5-10% glucose (w/w)
Cough syrup, 1 mg/mL dextromorphan
Infant Tylenol, 160 mg/5 mL acetaminophen
Seawater, 35 ppt = 35 g/kg NaCl
Miracle Grow Indoor Plant Food, 1% N, 1% P, 1 % K (w/w)
Requirements:

Choose a chemical solution that you use regularly at home or at work and list the name and concentration of the solution from the package label.
Describe where you use the solution, what you use it for, and any additional steps required to prepare it for use.
Use the internet or published MSDS to research and report on the:
Chemical name
Chemical formula
Molecular mass
(optional, but encouraged) Include a picture of the chemical structure
Using the concentration and the molecular mass, show how to convert the concentration into units of molarity.

A quick note about % solutions: check to see what type of % is being used!

% (w/w), weight-to-weight, or % by weight is calculated as the mass of the solute divided by the mass of the solvent and is common for solids dissolved in a liquid.

% (v/v), volume-to-volume), or % by volume is calculated as the volume of the solute divided by the volume of the solvent and is common for liquids dissolved in a liquid.

% (w/v), weight-to-volume, typically only used in chemistry for reporting solubilities

Also note that water has a density of 1g/mL, so weight and volume for aqueous solutions (solutions where water is the solvent) are interchangeable. Thus, % (w/w) and % (w/v) are the same for an aqueous solution.