Question

What are some common mistakes students make with stoichiometry of reactions between ions in solutions?

Answer 1

A failure to realize that BOTH mass and charge MUST be conserved in any chemical reaction.

Explanation:

Not only must mass be balanced in a chemical reaction, but charge must be balanced as well. If I start with 10 g, I must end with 10 g. Likewise, if the reactants have a certain charge, positive or negative, the products MUST have that same charge.

For example:

Lead nitrate + sodium chloride `rarr` Lead chloride`darr` + sodium nitrate.

As a net ionic equation:

`Pb^(2+) + 2Cl^(-) rarr PbCl_2(s)darr`

The reactants were neutral (`2^(+) + 2xx1^(-)`); so too the products!