Answer:
Al2(SO4)3 and Mg(OH)2
Explanation:
1. Al has a charge of 3-, and SO4 of 2-
when you cross multiply the charges you get
Al2 and (SO4)3
*the reason theres a bracket around the sulfate ion is that the charge 3 is not for oxygen only, but the entire sulphate ion*
Hence, Al2(SO4)3
2. Mg has a charge of 2- and OH of 1-
again cross multiply
Mg (you dont need to add the 1) and (OH)2
again, the bracket around OH means the charge appiles to Oxygen AND hydrogen
hence, Mg(OH)2
To find the Percent Composition of an atom, you use this formula:
Mass of element in the compound you're studying on ( in this case it's 5 since there is 5 Hydrogens) over the mass of the compound (which is here 79), Multiplied by 100 since you want a percent.
So we get:

So you get about:


So, the percent composition of Hydrogen in NH4HCO3 is 6.3%
Hope this Helps! :D
The volume of a sample of ammonia gas : 5.152 L
<h3>Further explanation</h3>
Given
0.23 moles of ammonia
Required
The volume of a sample
Solution
Assumed on STP
Conditions at T 0 ° C and P 1 atm are stated by STP (Standard Temperature and Pressure). At STP, Vm is 22.4 liters / mol.
So for 0.23 moles :
= 0.23 x 22.4 L
= 5.152 L
It would be an atom. Hope this helps! :)