Chapter 4. Reactions in Aqueous Solution Common Misconceptions

• Don’t forget that the rules of significant figures apply virtually to all the numerical problems we solve.

• Remember: Molarity is moles of solute per liter of solution, not per liter of solvent.

• The equation: only applies to dilution (that is, to the same substance when the concentration changes by adding/removing solvent). Your using of this equation to solve stoichiometry problems will be deemed as a misconception ( you can actually solve, mathematically speaking, stoichiometry problems with it –specifically when the mole- mole ratio is 1:1–, but we are doing chemistry here, not only mathematics).

• Pure water does not conduct electricity (it yields a very low concentration of ions).

• Strong electrolytes dissociate completely, weak electrolytes dissociate partially. Experiments are performed to find the difference, and we have some general rules. Also, you need to bear in mind that when we say something is insoluble, in actuality we mean poorly soluble.

• Keep in mind that the net ionic equation for the reaction between strong acids and strong bases is always: .

• Although they are close to one another, if the technique is performed correctly, the equivalence point and the end point of a titration are different. What do they refer to?

• An oxidation reaction does not necessarily require the presence, addition or removal of oxygen. Why?

• The oxidation number of an element may not relate at all to the position of the atom on the periodic table (we need to assign it following a set of rules that we memorize).

Reyes Chem 1A