To find the number of moles of ions in a solution, you need to consider the dissociation of the compound in water. In this case, you have 0.75 mol of potassium chloride (KCl) dissolved in 0.25 L of water.
When KCl dissolves in water, it dissociates into its constituent ions, K+ and Cl-. Since there is 1 K ion and 1 Cl ion per KCl molecule, when 0.75 mol of KCl is dissolved, you will have 0.75 mol of K+ ions and 0.75 mol of Cl- ions in the solution.
So, the total number of moles of ions (both cations and anions) in solution would be the sum of the moles of K+ and Cl- ions:
Total moles of ions = moles of K+ ions + moles of Cl- ions = 0.75 mol + 0.75 mol = 1.5 mol
Therefore, there are 1.5 moles of ions (both cations and anions) present in the solution when 0.75 mol of potassium chloride is dissolved in 0.25 L of distilled water.