Question

Write the chemical formula for potassium dichromate.

Answer 1

The symbol of potassium is ‘$\mathrm{K}$’, having a valency of 1⁺.

The formula of dichromate is ‘${\mathrm{Cr}}_2{\mathrm{O}}_7$’ with valency 2^-.

Step 1 –

Write the formula of potassium dichromate:

Symbol Valency

Potassium $\mathrm{K}$ 1⁺

Sulphur ${\mathrm{Cr}}_2{\mathrm{O}}_7$ 2^-

Step 2 –

Write each symbol with its valency:

$\mathrm{K}$ ${\mathrm{Cr}}_2{\mathrm{O}}_7$

Step 3 –

Interchanging the valencies:

$$\begin{gathered} \mathrm{K}{\mathrm{Cr}}_2{\mathrm{O}}_7 \\ \searrow \swarrow \\ {1}^{+}{2}^{-} \end{gathered}$$

The chemical formula of the compound potassium dochromate would be ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$.