Question

The formula of hydrogen phosphate of a metal is MHPO₄. Give the formula of the Metal bicarbonate.

Answer 1

• The molecular formula of the compound is always electrically neutral.
• That is the positive and negative charges of the ions or the radicals present in the chemical compounds add upto zero.
• One of the method used to write molecular formula is criss-cross method.

In criss-cross method,

• Write the symbols side by side, usually the one with positive valency first.
• Write the valency of each atom on the top of the symbol.
• To get simplest ratio, divide the valency numbers by their highest common factor(H.C.F). Ignore the (+) and (-) symbols of the radicals.
• Interchange the valencies of the radicals.
• Write the interchanged valency numbers to the lower right of the radicals.
• If the radical is a group of atoms and receives a valency number more than 1, enclose it within brackets.

In MHPO₄

The oxidation state of HPO₄ is -1.

Valency of Hydrogen phosphate is 1

So we can understand that the oxidation state of M is +1.

Formula of Metal bicarbonate is

Element Metal Bicarbonate

Symbol M HCO₃

Valency 1 1

Interchanging the valencies 1 1

Formula of Metal bicarbonate M₁(HCO₃)₁

Then the formula of metal bicarbonate is MHCO₃.