Help with chemistry please first 2 or any

If e is the symbol for an element, which two of the following symbols represent isotopes of the same element? 1. e2. e3. ea.1 and 2c.1 and 4b.3 and 4d.2 and 3

What happens to the concentration of hydronium ions as the ph of a solution increases? a. hydronium ion concentration stays the same b. hydronium ion concentration decreases c. hydronium ion concentration increases

What is the mass of 0.750 mole of aluminum oxide, al2o3?