Solid Al(NO3)3 is added to distilled water to produce a solution

Solid Al(NO3)3 is added to distilled water to produce a solution in which the concentration of nitrate, [NO3-], is 0.10 M. What is the concentration of aluminum ion, [Al3+], in this solution?

(A) 0.010 M

(B) 0.033 M

(C) 0.066 M

(D) 0.10 M

(E) 0.30M

Answer and Explanation: Looking at the formula Al(NO3)3, we notice that for one Al ion, there are three NO3 ions. Therefore when aluminum nitrate dissociates in water, it produces one aluminum ion and three nitrate ions per each formula unit.

Since we know the concentration of nitrate is 0.1, the concentration of aluminum should be 1/3 of that.

0.1 (1/3) = 0.033 M (B)

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