Question

on dissolving calcium oxide in water it gives a colourless solutin how do you know the solutin formed is an acid or base

Answer 1

CaO +H2O⇒Ca(OH)2 + Δ

THE SOLUTION FORMED IS CALCIUM HYDROXIDE IT IS A BASE 
TO CHECK THE SOLUTION IS A BASE:
1)TAKE A RE LITMUS PAPER.
2)DIP A RED LITMUS PAPER INTO THE SOLUTION IT CHANGES TO BLUE COLOR.IT SHOWS,IT IS A BASE.

Answer 2

you can check it by litmus paper red litmus paper turns blue under basic (i.e. alkaline) conditions and  Blue litmus paper turns red under acidic conditions