These 3 questions refer to the following experiment. Some Fe(NO 3 ) 3 solution is added…

These 3 questions refer to the following experiment. Some Fe(NO₃)₃ solution is added to KSCN solution and a dark red colour appears. This colour is caused by [Fe(SCN)]²⁺, which is formed by the reaction :
Fe³⁺ (aq) + SCN^– (aq) \(\text { ⇌ }\) [Fe(SCN)]²⁺
Experiments show this colour becomes deeper upon addition of more Fe(NO₃)₃ or KSCN. The colour disappears when Na₂HPO₄ is added. Use one or more of the interpretations below.
(a ) Unreacted Fe³⁺ (aq) is present in the original equilibrium mixture.
(b ) Unreacted SCN^– (aq) is present in the original equilibrium mixture.
(c ) Colour change indicates a new equilibrium ;
[Fe(SCN)²⁺ (aq)] has been reduced.
(d ) Colour change indicates a new equilibrium ;
[Fe(SCN)²⁺ (aq)] has been increased.
The disappearance of colour on addition of Na₂HPO₄ supports