Question

molar mass of a compound containing Al3+ ion and OH- ion?

Answer 1

Answer: The molar mass of a compound containing $Al^{3+}$ ion and $OH^-$ ion is 78 g/mol

Explanation:

For formation of a neutral ionic compound, the charges on cation and anion must be balanced. The cation is formed by loss of electrons by metals and anions are formed by gain of electrons by non metals.

Here aluminium has an oxidation state of +3 called as $Al^{3+}$ cation and $OH^{-}$ is an anion with oxidation state of -1. Thus they combine and their oxidation states are exchanged and written in simplest whole number ratios to give neutral $Al(OH)_3$

Molar mass is defined as the mass in grams of 1 mole of a substance.

Atomic Mass of Aluminium (Al) = 27 g

Atomic Mass of Oxygen (O) = 16 g

Atomic Mass of Hydrogen (H) = 1 g

Molecular mass of  $Al(OH)_3$ = 27+3(16)+3(1) g = 78 g

Thus molar mass of a compound containing $Al^{3+}$ ion and $OH^-$ ion is 78 g/mol