Question

Write the molecular formula
(A) Sodium carbonate
(B) Hydrogen chloride
(C) Calcium carbonate
(D) Aluminium oxide
(E) Calcium phosphate
(F) Aluminium bicarbonate
(G) Zinc sulphate

Answer 1

The molecular formula of the above given compounds can be obtained by using the criss-cross method. In this method, the numerical value, i.e. the ionic charges of each element is crossed over which becomes the subscript of the other ion.

Complete step by step solution:
By using the criss-cross method, the molecular formula of the given compounds can be obtained in the following way
(A) Sodium carbonate:
Considering the ionic charges,
Sodium has charge $N{{a}^{1+}}$
Carbonate has charge $C{{O}_{3}}^{2-}$
$Na$ $CO{}_{3}$
1+ 2-
After criss-crossing, we get
$N{{a}_{2}}CO{}_{3}$
Thus, the molecular formula of Sodium carbonate is $N{{a}_{2}}CO{}_{3}$
(B) Hydrogen chloride:
Considering the ionic charges,
Hydrogen has charge ${{H}^{1+}}$
Chloride has charge $C{{l}^{1-}}$
$H$ $Cl$
1+ 1-
After criss-crossing, we get
$HCl$
Thus, the molecular formula of Hydrogen Chloride is $HCl$
(C) Calcium carbonate:
Considering the ionic charges,
Calcium has charge $C{{a}^{2+}}$
Carbonate has charge $C{{O}_{3}}^{2-}$
$Ca$ $CO{}_{3}$
2+ 2-
After criss-crossing, we get
$CaC{{O}_{3}}$
Thus, the molecular formula of Calcium carbonate is $CaC{{O}_{3}}$
(D) Aluminium oxide:
Considering the ionic charges,
Aluminium has charge $A{{l}^{3+}}$
Oxygen has charge ${{O}^{2+}}$
$Al$ $O$
3+ 2-
After criss-crossing, we get
$A{{l}_{2}}{{O}_{3}}$
Thus, the molecular formula of Aluminium oxide is $A{{l}_{2}}{{O}_{3}}$
(E) Calcium phosphate:
Considering the ionic charges,
Calcium has charge $C{{a}^{2+}}$
Phosphorus has charge ${{(P{{O}_{4}})}^{3-}}$
$Ca$ $P{{O}_{4}}$
2+ 3-
After criss-crossing, we get
$C{{a}_{3}}{{(P{{O}_{4}})}_{2}}$
Thus, the molecular formula of Calcium phosphate is $C{{a}_{3}}{{(P{{O}_{4}})}_{2}}$
(F)Aluminium bicarbonate:
Considering the ionic charges,
Aluminium has charge $A{{l}^{3+}}$
Bicarbonate has charge $HC{{O}_{3}}^{2-}$
$Al$ $HC{{O}_{3}}$
3+ 2-
After criss-crossing, we get
$A{{l}_{2}}{{(C{{O}_{3}})}_{3}}$
Thus, the molecular formula of Aluminium bicarbonate is $A{{l}_{2}}{{(C{{O}_{3}})}_{3}}$
(G)Zinc sulphate:
Considering the ionic charges,
Zinc has charge $Z{{n}^{2+}}$
Sulphate has charge ${{(S{{O}_{4}})}^{2-}}$
$Zn$ $S{{O}_{4}}$
2+ 2-
After criss-crossing, we get
$ZnS{{O}_{4}}$
Thus, the molecular formula of Zinc sulphate is $ZnS{{O}_{4}}$

Note: Sodium carbonate is commonly known as washing soda, used in cleaning products. Calcium carbonate is a dietary supplement used during calcium deficiency in the body.