AQA A Level Chemistry - Inorganic HELP!

An aqueous solution Y is known to contain one type of group 2 metal ion and one type of negative ion.
Aqueous solutions of sulfuric acid and magnesium nitrate are added to separatesamples of solution Y. The observations are shown in Table 5.

Table 5
Solution added Observation with solution Y
Sulfuric acid A white precipitate forms
Magnesium nitrate A white precipitate forms

7 . 1 Suggest the identity of the group 2 metal ion present in solution Y.
Write an ionic equation, including state symbols, for the reaction that takes place when sulfuric acid is added to solution Y.
[2 marks]
Group 2 metal ion

Ionic equation

0 7 . 2 Suggest the identity of the negative ion present in solution Y.
Write an ionic equation, including state symbols, for the reaction that takes place when magnesium nitrate is added to solution Y.
[2 marks]

Negative ion

Ionic equation

You need to show your attempt.What are the ions present in Y ?

I found out the ions present are Ba^2 and OH^-

yup

how tho? 😂

When sulfuric acid is added, a white ppt forms. It is due to BaSO4. So the metal ion present is Ba2+.

When Mg(NO3)2 is added, a white ppt forms. It is due to Mg(OH)2. So the anion present is OH-.

how do you know it's those elements???