# What is the chemical formula for cobalt (II) hydrogen carbonate?

#### Risposta:

The chemical formula for cobalt(II) hydrogen carbonate is "Co"("HCO"_3)_2.

#### Spiegazione:

The name tells you that this is an ionic compound, made of cobalt(II) ions and hydrogen carbonate ions.

The symbol for the cobalt(II) ion is "Co"^"2+".

The symbol for the hydrogen carbonate ion is "HCO"_3^"-" (you have memorized the formulas of the ioni poliatomici, haven't you?).

So, the formula contains "Co"^"2+", "HCO"_3^"-".

We need two "-" charges to balance the "2+" charges on the "Co".

Thus, we need two hydrogen carbonate ions, so we enclose the formula in parentheses followed by a subscript 2.

La formula è "Co"("HCO"_3)_2