Answer
The Correct Formulas are :
$LiF$
$Fe_{2}S_{3}$
$Al(OH)_{3}$
$Zn(NO_{3})_{2}$
$CaCl_{2}$
Work Step by Step
The given compounds are ionic compounds. The net charge on each of the compounds must be zero. The charges of ions are given below:
Lithium : +1
Fluoride: -1
Iron(iii): +3
Sulfide: -2
Aluminum: +3
Hydroxide: -1
Zinc: +2
Nitrate: -1
Calcium: +2
Chloride: -1
1) The given formula is $LiF_{2}.$
The charge on Lithium is +1 and on Fluoride is -1.To balance the charge there must be one fluoride ion with lithium.
The formula will be $LiF$
2) The given formula is $Fe_{3}S.$
The charge on Iron is +3 and on Sulfide is -2. To balance the charge there must be three fluoride ion with two Iron.
The formula will be $Fe_{2}S_{3}$
3) The given formula is $AlOH_{3}.$
The charge on Aluminium is +3 and on Hydroxide is -1. To balance the charge there must be three Hydroxide ion with one Aluminium.
The formula will be $Al(OH)_{3}$
4) The given formula is $Zn_{3}(NO)_{2}.$
The charge on Zinc is +2 and on Nitrate is -1. To balance the charge there must be Two Nitrate ion with one Zinc.
The formula will be $Zn(NO_{3})_{2}$
5) The given formula is $CaCl^{+}.$
The charge on Calcium is +2 and on Chloride is -1. To balance the charge there must be Two Chloride ion with one Calcium.
The formula will be $CaCl_{2}$.
