Question

In the following question, a positive and a negative radical is listed. Using the criss-cross method, write the formula for the compound that is formed and name the compound.

${\mathrm{Ca}}^{+2}$ ${\mathrm{HSO}}_4^{-1}$

Answer 1

Step-1: Identify the acidic and basic radicals or positive and negative ions:

• Positive ion or cation or basic radical: ${\mathrm{Ca}}^{+2}$
• Negative ion or anion or acidic radical: ${\mathrm{HSO}}_4^{-1}$

Step-2: Write the valency of the ion:

• Valency is written as a positive or negative charge on the ion as a superscript on the right hand side.
• Valency of ${\mathrm{Ca}}^{+2}$ is 2 Valency of ${\mathrm{HSO}}_4^{-1}$ is 1

Step-3: Write the valency of the ion below or above its symbol without the + or - sign:

Symbol of radical $\mathrm{Ca}$ ${\mathrm{HSO}}_4$

Valency of the radical 2 1

Step-4: Transpose the valency by criss-cross:

• Criss-cross multiplication is a method where the valency of a cation is written as a subscript of anion and vice-versa.

$$\begin{gathered} \mathrm{Ca}{\mathrm{HSO}}_4 \\ \searrow \swarrow \\ 21 \end{gathered}$$

Step-5: Write the outcome of criss-cross and simplify by dividing using a common factor if needed

• ${\mathrm{Ca}}_1{\left({\mathrm{HSO}}_4\right)}_2$ or $\mathrm{Ca}{\left({\mathrm{HSO}}_4\right)}_2$

Step-6: Write the chemical formula and chemical name

• Cation is written first followed by the anion.
• The chemical formula of the compound is $\mathrm{Ca}{\left({\mathrm{HSO}}_4\right)}_2$
• Name of the cation is written followed by the anion.
• Cation is written is Calcium and anion is Bisulphate or Hydrogen sulphate.
• The chemical name of the compound is Calcium bisulphate or Calcium hydrogen sulphate.