Which combination will result is a precipitate forming?

Which combination will result is a precipitate forming?

(A) NaOH(aq) and HCl(aq)

(B) NaOH(aq) and FeCl3(aq)

(C) NaNO3(aq) and FeCl3(aq)

(D) Zn(s) and HCl(aq)

Solution:

When two aqueous solutions mix and form a solid, the solid is called a precipitate. Let's do this problem step by step.

Step 1: Predict the products for each reaction doing the double deplacement. AB+CD --> AD +CB A. NaOH(aq) and HCl(aq) ---> NaCl +HOH

B. NaOH(aq) and FeCl3(aq) ---> NaCl + Fe(OH)3

C. NaNO3(aq) and FeCl3(aq) --> NaCl + FeNO3

D. Zn(s) and HCl(aq)= this choice is out because it is a single replacement reaction, not double, and would not form a precipitate.

Step 2: Identify if any of the products is insoluble using solubility table (I put the one given on the Chemistry Regents Exam). Insoluble product is the precipitate.

A. NaOH(aq) and HCl(aq) ---> NaCl -soluble +HOH - water, not solide

B. NaOH(aq) and FeCl3(aq) ---> NaCl -soluble+ Fe(OH)3 - insoluble, precipitate! B is the correct answer.

C. NaNO3(aq) and FeCl3(aq) --> NaCl-soluble + FeNO3-soluble

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