The atomic weight of Barium (Ba) is given as 137-3 in the question. To find the equivalent weight of Ba(OH)2, we need to consider the number of moles of Ba(OH)2 that provide one mole of hydroxide ions (OH^-).

Ba(OH)2 consists of one Ba atom and two OH^- ions. Since the valency of Ba is +2 and the valency of OH^- is -1, it means Ba(OH)2 releases 2 moles of OH^- ions per mole.

Therefore, the equivalent weight of Ba(OH)2 is the atomic weight of Ba divided by 2.

When we calculate 137-3/2, we get 68.65-7.

Hence, option 1, 85-7, is the correct answer.

Equivalent weight is a concept used in stoichiometry to determine the amount of a substance that reacts with another substance. It is the amount of a substance that contains one mole of reactive units such as atoms, ions, or molecules. In this case, the equivalent weight of Ba(OH)2 represents the amount of Ba(OH)2 needed to react with one mole of a substance that