Question

second photo is for your reference. thanks!

In this step, you add xSCN to oneof the our escoi y a. If your solution has Fe", s te portions from Step 12A. ,what change should you expect to observe? b. Write a balanced chemical equation for the reaction between Fe" and KSCH. equation Step 13 In this step, you first add Naf to one of the four decantate portions NH&SCN in ethanol. from Step 12A; then, you add a. If your solution has Co", what change should you expect to observe? b. What is the purpose of NaF in this step? c. Write a balanced chemical equation for the reaction involving NaF appropriate for this step. with NH.SCN. d. Write a balanced chemical equation for the reaction of Co NH SCN is added in this step, the solution turns red, similar to Step 12B, even if the solution has Co present. If this should happen, what would be a suitable remedy? Step 12B: Test for Iron Fo one portion, add 1 or 2 drops of 0.2 M KSCN, A blood red solution, due to Fe(SCN)3 proves the presence of iron. What Happens In This Step? Thiocyanate anion, SCN forms a Lewis acid-base complex with Fe that prod characteristic blood-red solution. Fe"(aq) + 6SCNTaq) → Fe(SCN)-(aq) Blood-Red Solution Confirms the Presence of Iron STEP 13: Test for Cobalt To the second portion of the solution prepared in Step 12A, add 10 drops of 1M NaF solution and mix well by stirring. Then add 10-20 drops of a saturated solution of NH4SCN (ammonium thiocyanate) in ethyl alcohol. The formation of a blue solution due to Co(SCN)42- proves the presence of Co2 Thiocyanate ion, SCN-, also forms a Lewis acid-base complex with Co2*, Co(SCN)42- whichis light blue. However, if Fe* isalso present, the blood-red color of Fe(SCN) 3 will obscure the light blue color of Co(sCN. Therefore, fluoride ions are added first to sequester the Fe ions, so that they don't react with SCN more stable complex with fluoride ions, FeF, than with SCN- in the form of ammonium thiocya complex. Iron(III) forms a uoride ions, FeFs, than with SCN ions. Then, SCN- ions nate in ethyl alcohol, is added to form the Co(SCN)2- Light blue in alcohol layer Confirms the Presence of Cobalt cohol than in water, so if you the cloating above out, Co(SCN) is more stable in ethyl alcohol than in t turns o ammonium (br of the Co(scn compleco ou shouid sald the light the more dense aqueous layer should see the thiocyanate solution 06

Answer 1

(a) Fe⁺³ reacts with SCN^- to form a deep red coloured complex.

(b) Fe⁺³ (aq) + SCN^- (aq) = Fe (SCN)⁺² (aq)

Step 13:

(a) Co⁺² forms a light blue coloured complex with SCN-. Hence the solution turns light blue.

(b) F^- is added to separate Fe⁺³ from Co⁺². Fe⁺³ reacts with fluoride ion and forms a stabler complex. For the reason; it dies not react with SCN-. SCN- reacts only with Co+2.

(c) Co⁺² (aq) + 4 SCN^- (aq) = [Co (SCN)₄]^-2 (aq)

(d) Add NaF. F- replaces the SCN- ion from deep red coloured [Fe (SCN)]⁺² and SCN- can react with Co+2.