Eqimolar solutions of these are prepared separetely which one of these will record highest value of ph and WHY( with proper scientifical explanations)?

1)BaCl₂

2)AlCl₃

₃₎LiCl

₄₎BeCl₂

BaCl2 because it is the salt of Ba (OH)2 , which is a strong base.
Ba (OH)2+ HCl--> BaCl2+ H2O
Hence, BaCl2 hydrolysed to give most alkaline solutions among all the salts provided in the question and adds to highest PH.

The most basic among all these will have the highest pH value. Also, basicity increases down a group while it decreases from left to right in a period. Hence, among the four, Barium Chloride will have the highest pH value.

Equimolar solutions of the given chlorides when prepared in water forms their respective hydroxides.
Be(OH)2 is amphoteric, but hydroxides of all other are basic in nature. Higher the basic character, higher will be the pH and the basic character increases as we go down the group. Li belongs to period 1, Al belongs to period 3 and Ba belongs to period 6. Therefore, hydroxide of Ba is most basic and will have the highest pH.