Answer
The formula for potassium nitrate is KNO$_3$.
The formula for ammonium carbonate is (NH$_4$)$_2$CO$_3$.
Work Step by Step
According to the periodic table, potassium is an alkali metal and has a valence of 1+. Nitrate, according to Table 2.2 on page 65 in our book, has the formula NO$_3$$^-$. These elements combine in a 1:1 ratio to make potassium nitrate (KNO$_3$).
Ammonium's formula is NH$^+$. Carbonate's formula, according to Table 2.2 on page 65 of our book, is CO$_3$$^{2-}$. These elements combine in a 2:1 ratio, meaning there should be two ammonium ions for every carbonate ion. The formula for ammonium carbonate is (NH$_4$)$_2$CO$_3$.
