Solution Stoichiometry

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Hydrochloric acid solution

Lactic acid solution

Ethyl alcohol solution

Pure sodium chloride

Try to classify the following substances as electrolytes or nonelectrolytes…

Slide 11

Answers to Electrolytes

ELECTROLYTES:

NONELECTROLYTES:

Tap water (weak)

NaCl solution

HCl solution

Lactate solution (weak)

Pure water

Sugar solution

Ethanol solution

Pure NaCl

Slide 12

Ionic Compounds “Dissociate”

NaCl(s) 

AgNO3(s) 

MgCl2(s) 

Na2SO4(s) 

AlCl3(s) 

Na+(aq) + Cl-(aq)

Ag+(aq) + NO3-(aq)

Mg2+(aq) + 2 Cl-(aq)

2 Na+(aq) + SO42-(aq)

Al3+(aq) + 3 Cl-(aq)

Slide 13

The reason for this is the polar nature of

the water molecule…

Positive ions associate with the negative

end of the water dipole (oxygen).

Negative ions associate with the positive

end of the water dipole (hydrogen). Ions tend to stay in solution where they can conduct a current rather than re-forming a solid.

Slide 14

Some covalent compounds IONIZE in solution

Covalent acids form ions in solution, with the

help of the water molecules.

For instance, hydrogen chloride molecules,

which are polar, give up their hydrogens to

water, forming chloride ions (Cl-) and

hydronium ions (H3O+).

Slide 15

Other examples of strong acids include:

Sulfuric acid, H2SO4

Nitric acid, HNO3

Hydriodic acid, HI

Perchloric acid, HClO4 Strong acids such as HCl are completely ionized in solution.

Slide 16

Many of these weaker acids

are “organic” acids that contain a “carboxyl” group.

The carboxyl group does not easily give up its

hydrogen.

Weak acids such as lactic acid usually ionize less than 5% of the time.

Slide 17

Other organic acids and their sources include:

Citric acid – citrus fruit

Malic acid – apples

Butyric acid – rancid butter

Amino acids – protein

Nucleic acids – DNA and RNA

Ascorbic acid – Vitamin C

This is an enormous group of compounds;

these are only a few examples. Because of the carboxyl group, organic acids are sometimes called “carboxylic acids”.