Question

. Give the concentration of the following in terms of Molarity.

          a. The molarity of hydroxide ions in a 4.25M solution of barium hydroxide.

          b. The molarity of sodium ions in a 11.5M sodium phosphate solution.

Answer 1

a) Here we are dissolving Ba(OH)₂ ,then finding out concentration of hydroxide ion in the aqueous solution.

• Dissolution of Barium hydroxide in water or write down balanced dissolution equation.

             Ba(OH)₂   +    H₂O        Ba²⁺     +      2 OH^-

•     Use the coefficient from this equation to calculate concentration of the individual ions in aqueous solution.

Molarity of Hydroxide ion (OH^-) :-

So molarity of OH^- ion in 4.25 M solution of Ba(OH)₂ solution is 8.5 M .

b) Sodium phosphate are salt of sodium (Na⁺) and phosphate(PO₄^3-) , some examples are:-

Here I am calculating concentration of sodium in sodium dihydrogen sulphate (NaH₂PO₄).

• Dissolution of sodium phosphate in water or write down balanced dissolution equation.

             NaH₂PO₄ +    H₂O        Na⁺     +      H₂PO^-₄

•     Use the coefficient from this equation to calculate concentration of the individual ions in aqueous solution.

Molarity of sodium ion (Na⁺) :-

So molarity of Na⁺ ion in 11.5 M solution of NaH₂PO₄ solution is 11.5M .Similarly you can calculate sonium ion concentration in other sodium phosphate by considering 2 or 3 mol of sodium ion.