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

##### 1 Answer
Jan 7, 2016

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 $\rightarrow$ Lead chloride$\downarrow$ + sodium nitrate.

As a net ionic equation:

$P {b}^{2 +} + 2 C {l}^{-} \rightarrow P b C {l}_{2} \left(s\right) \downarrow$

The reactants were neutral (${2}^{+} + 2 \times {1}^{-}$); so too the products!