Question

Question #32f25

Answer 1

don't forget that Ba(OH)2 contains 3 ions (1x Ba and 2x -OH ions) thus correct answer is 0.00075 x 3 = 0.00225

Explanation:

conc = mol / vol (in dm^3)
so
mol = conc x vol (in dm^3)
mol = 0.025 * (30/1000)
mol = 0.00075
but this is moles of Ba(OH)2.
therefore total moles of ALL ions = moles of Ba2+ ions + 2 x moles of hydroxide ions
= 0.00075 + (2 x 0.00075)
= 0.00225
=)