Ion concentration refers to the molar concentration of an ion in solution. It ma

Question

Ion concentration refers to the molar concentration of an ion in solution. It may be identical to, or greater or less than, the molar concentration of the compound containing the ion that was used to make the solution. For soluble salts, the molarity of a particular ion is equal to the molarity of that compound times the subscript for that ion. For example, 1 M of AICI3 is 1 What is the concentration of K+ in 0. 15 M of K2S? If CaCl-2 is dissolved in water, what can be said about the concentration of the Ca2+ ion? A scientist wants to make a solution of tribasic sodium phosphate, Na3P04l for a laboratory experiment. How many grams of Na3P04 will be needed to produce 425 mL of a solution that has a concentration of Na+ ions of 1. 30 M?

Explanation / Answer

A)

If you have 2 moles of K+ for every mole of K2S and Molarity (M) is Moles per Liter. Then you know that you have 0.30 M of K2S. The way that you do that is setting up a series of conversion factors like so:

(0.15moles k2s/liter) x (2 moles of K/ 1 mole of K2S) = 0.30 moles k/ liter.

The moles of K2S cancel out and you are left with moles of K per liter.

B) half of that concentration of Cl- ion

C)Since there are 3 moles Na+ in 1 mole of Na3PO4 the concentration of Na3PO4 needed is 1.3/3 M = 0.433 M.
And 0.433 moles Na3PO4/L = 163.94*0.433 = 70.98g/L.
Which are 70.98*425/1000 g = 30.169 g in 3425 mL.

Hence answer is 30.169 gms

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