30. If the formula of metal sulphite of a metal M is MSO3, give the formula of its
(a) phosphate
(b) hydrogen phosphate
(c) chloride
30. If the formula of metal sulphite of a metal M is MSO3, give the formula of its
(a) phosphate
(b) hydrogen phosphate
(c) chloride
- Formula represents a molecule of an element or compound.
- It is a combination of the symbols of the constituent elements along with the number of atoms of individual elements present in a molecule.
Derivation of Formulae of Compounds from the Constituent Radicals
A chemical compound is always electrically neutral.
This means in a molecule of a compound, the positive valencies are balanced by the negative valencies.
The formula of the compound can be derived by using a shortcut method known as criss-cross method.
- The positive radical is written first followed by the negative radical.
- The valencies of the ions or radicals are written below the radicals without positive and negative signs.
- The valencies should be interchanged and written as subscripts on the right side of the respective ions.
- If the valencies have common factors, they are divided by the highest common factor.
- The radicals containing more than one atom are enclosed in brackets if the number of radicals present in a molecule is more than one.
- The given formula of metal sulphite of a metal M is MSO3
- The sulphite ion (SO42-) is divalent and carry -2 charge.
- In order to neutralise the -2 charge on sulphite ion, M ion should be divalent and carry +2 charge. So, from the formula, we find that the M ion is divalent and has +2 charge.
(a) Formula of metal phosphate:
The phosphate ion( PO4-3) is trivalent and carry -3 charge. And we already know that the metal ion has +2 charge.
So, the formula of the metal phosphate will be M3(PO4)2.
(b) Formula of metal hydrogen phosphate:
The hydrogen phosphate ion( HPO4)-2 is divalent and carry -2 charge. And we already know that the metal ion has +2 charge.
So, the formula of the metal hydrogen phosphate will be MHPO4.
(c) Formula of metal chloride:
The chloride ion(Cl-) is monovalent and carry -1 charge. And we already know that the metal ion has +2 charge. In order to neutralise the +2 charge on the metal ion, two chloride ions are necessary.
So, the formula of the metal hydrogen chloride will be MCl2.
- Formula represents a molecule of an element or compound.
- It is a combination of the symbols of the constituent elements along with the number of atoms of individual elements present in a molecule.
Derivation of Formulae of Compounds from the Constituent Radicals
A chemical compound is always electrically neutral.
This means in a molecule of a compound, the positive valencies are balanced by the negative valencies.
The formula of the compound can be derived by using a shortcut method known as criss-cross method.
- The positive radical is written first followed by the negative radical.
- The valencies of the ions or radicals are written below the radicals without positive and negative signs.
- The valencies should be interchanged and written as subscripts on the right side of the respective ions.
- If the valencies have common factors, they are divided by the highest common factor.
- The radicals containing more than one atom are enclosed in brackets if the number of radicals present in a molecule is more than one.
- The given formula of metal sulphite of a metal M is MSO3
- The sulphite ion (SO42-) is divalent and carry -2 charge.
- In order to neutralise the -2 charge on sulphite ion, M ion should be divalent and carry +2 charge. So, from the formula, we find that the M ion is divalent and has +2 charge.
(a) Formula of metal phosphate:
The phosphate ion( PO4-3) is trivalent and carry -3 charge. And we already know that the metal ion has +2 charge.
So, the formula of the metal phosphate will be M3(PO4)2.
(b) Formula of metal hydrogen phosphate:
The hydrogen phosphate ion( HPO4)-2 is divalent and carry -2 charge. And we already know that the metal ion has +2 charge.
So, the formula of the metal hydrogen phosphate will be MHPO4.
(c) Formula of metal chloride:
The chloride ion(Cl-) is monovalent and carry -1 charge. And we already know that the metal ion has +2 charge. In order to neutralise the +2 charge on the metal ion, two chloride ions are necessary.
So, the formula of the metal hydrogen chloride will be MCl2.
