In the reaction between lead(II) nitrate and sodium chloride, what, if any, are the spectator ions

Explanation:

Spectator ions are ions in a solution/reaction that do not take part in a chemical reaction (hence are called "spectator" ions). They can be identified when they are found both in the reactant and product sides.

The reaction between lead(II) nitrate, Pb(NO₃)₂ and sodium chloride, NaCl is illustrated below

Pb(NO₃)₂ + 2NaCl ⇒ PbCl₂ + 2NaNO₃

According to solubility rules, all the compounds above (with the exception of PbCl₂) are all soluble and would dissociate when involved in a reaction.

Hence, the ionic equation based on the description above will be

Pb²⁺ + 2NO₃⁻ + 2Na⁺ + 2Cl⁻  ⇒  PbCl₂ + 2Na⁺ + 2NO₃⁻

From the above ionic equation, it can be noted that both 2NO₃⁻ and 2Na⁺ are found on both the reactant and product side and are hence the spectator ions.

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)