Fe+3 + SCN- ==Fe(SCN)+2
if adding NaOH will form precipitates, but what is the precipitates' formula?
And after this reaction, if we add HCl to the reaction, will the precipitates dessolve? What does the HCl affect the reaction? THX
The ppt probably is Fe(OH)3 and that is soluble in HCl.
Remember (Fe^+3)(SCN^-) = Fe(SCN)^+2
and Fe(SCN)^+2/(Fe^+3)(SCN^-)= Kformation so a complex FeSCN^+2 forms when Fe^+3 and SCN^- are high enough. If NaOH is added, then we are raising (OH^-) from the NaOH to a high level so that Ksp for Fe(OH)3 is exceeded and a ppt of Fe(OH)3 forms.
Remember (Fe^+3)(OH^-)^3 = Ksp.
Probably the red colored FeSCN^+3 complex disappears, also, because the pptn of Fe(OH)3 removes so much Fe^+3.
Adding HCl dissolves the ppt because H^+ is large (from the HCl) which reduces the OH^- (because of the
(H^+)(OH^-) = Kw and if the OH^- is reduced enough, Ksp for Fe(OH)3 is no longer exceeded and it dissolves.
Thanks a lot!!!
I think I got it!!!
The balanced equation is: Fe+3 + SCN- == Fe(SCN)+2.
When NaOH is added to the reaction, it forms a precipitate. The precipitate is Fe(OH)3, which is iron(III) hydroxide.
Fe+3(aq) + 3OH-(aq) == Fe(OH)3(s)
If HCl is added to the reaction, it will dissolve the precipitate. HCl reacts with Fe(OH)3 and forms a soluble complex called FeCl3.
Fe(OH)3(s) + 3HCl(aq) == FeCl3(aq) + 3H2O(l)
HCl affects the reaction by providing chloride ions (Cl-) that combine with iron(III) ions (Fe+3) to form the soluble complex FeCl3. This complex is soluble in water and does not form a precipitate.
To determine the precipitate formed, we need to consider the solubility rules. In this case, the reaction involves the formation of a complex ion Fe(SCN)+2. However, we need additional information about the solubility of this complex ion to determine if it will precipitate.
Regarding the effect of HCl on the reaction, let's analyze each part of the reaction:
1. Adding NaOH:
Fe+3 + SCN- + 3NaOH → Fe(SCN)3 + 3Na+ + 3OH-
In this step, we add NaOH to the reaction. Sodium hydroxide (NaOH) is a strong base and will cause the formation of hydroxide ions (OH-) in the solution. If the resulting hydroxide ions react with any cations present, it can lead to the formation of insoluble hydroxide precipitates.
2. Formation of Fe(SCN)3:
Fe+3 + SCN- → Fe(SCN)+2
In this step, the complex ion Fe(SCN)+2 is formed. Whether this complex is soluble or forms a precipitate depends on its individual solubility properties.
If Fe(SCN)+2 is soluble, then there will be no precipitate formed. However, if it is insoluble, a precipitate will form.
Regarding the effect of HCl on the reaction, we need to consider its acidic nature. When an acid, such as HCl, is added to a solution containing a precipitate, it can dissolve the precipitate by reacting with the ions present. In this case, if Fe(SCN)+2 forms a precipitate, adding HCl could potentially dissolve it.
To summarize, without additional information on the solubility of Fe(SCN)+2, we cannot determine the formula of the precipitate formed. However, if it does precipitate, adding HCl may dissolve the precipitate due to its acidic nature.