Urgent quick question for chemistry

Question

Which of the following reagents cannot be used to differentiate sodium hydroxide solution from sodium chloride solution?

A Aqueous iron(III) nitrate

B Aqueous copper(II) nitrate

C Aqueous lithium nitrate

D Aqueous ammonium nitrate

I put C as my answer but I am unsure which is correct. I’m hoping for a detailed explanation for each option, and explain clearly how to find out which reagent cannot be used to differentiate the two sodium solutions, thanks in advance! :)

Answer 1

Let's look at the reaction of each reagent with BOTH NaCl and NaOH:

Iron(III) nitrate, Fe(NO3)3

Fe(NO3)3(aq) + 3NaCl(aq) ==> FeCl3(aq) + 3 NaNO3(aq) = No Reaction b/c all are soluble and dissociate

Fe(NO3)3(aq) + 3NaOH(aq) ==> Fe(OH)3(s) + 3 NaNO3(aq)

Conclusion: Fe(NO3)3 will differentiate because of the formation of a precipitate

Copper(II) nitrate, Cu(NO3)2

Cu(NO3)2(aq) + 2NaCl(aq) ==> CuCl2(aq) + 2NaNO3(aq) = No Reaction b/c all soluble and all dissociate

Cu(NO3)2(aq) + 2NaOH(aq) ==> Cu(OH)2(s) + 2NaNO3(aq)

Conclusion: Cu(NO3)2 will differentiate because of the formation of a precipitate

Lithium nitrate, LiNO3

LiNO3(aq) + NaCl(aq) ==> No Reaction b/c all species dissociate completely and all are soluble

LiNO3(aq) + NaOH(aq) ==> No Reaction b/c all species dissociate completely and all are soluble

Conclusion: LiNO3 will not differentiate

Ammonium nitrate, NH4NO3

NH4NO3(aq) + NaCl(aq) ==> No Reaction b/c all species dissociate completely and all are soluble

NH4NO3(aq) + NaOH(aq) ==> No Reaction b/c all species dissociate completely and all are soluble

Hopefully, this answers and explains your question Recall that when all products are soluble and they dissociate completely, there will be NO REACTION.