Lab Le Chatelier's Principle Lesson 4

Part I Thymol Blue (blue) + H+ ⇌ Thymol Blue (yellow) + OH- HOH  Na+ + OH- Add HCl  H+ + Cl- Add NaOH spectator stress stress spectator Right yellow OH- lowers H+ left blue

Part II yellow orange Energy + 2CrO42- + 2H+ ⇌ Cr2O72- + H2O(l) + + Ba2+ OH- ⇌ ⇌ BaCrO4(s) HOH

Part III ⇌ yellow brown Fe3+(aq) + SCN-(aq) ⇌ FeSCN2+(aq) + 3OH- Fe(OH)3(s)

Part IV Co(H2O)62+ + 2Cl- ⇌ Co(H2O)4Cl22- + 2H2O(l) pink blue

Part V light blue powder blue ppt Cu(H2O)42+ + 2NH3 ⇌ Cu(OH)2(s) + 2NH4+ + 2H2O + + 4NH3 H+ ⇌ ⇌ Cu(NH3)42+ violet NH4+ + 2OH-

Energy + 2CrO42- + 2H+ ⇄ Cr2O72- + H2O(l) yellow orange Acid is H+ Base is OH- Acids react with bases H+ + OH- → H2O(l) Stress Shift Add HCl right Add K2CrO4 right Add K2Cr2O7 left

yellow orange Energy + + ⇄ Cr2O72- + H2O(l) 2CrO42- 2H+ + Ba2+ + BaCrO4(s) ⇌ OH- ⇌ HOH HCl 5 drops 6 M (lots!) shifts right- all CrO42- changes to Cr2O72- Ba(NO3)2 no CrO42- -no reaction NaOH left- makes CrO42- yellow ppt

1. Explain the colour changes observed when Fe(NO3)3, KSCN, and NaOH were added to the thiocyanairon equilibrium system. Start by writing the equilibrium equation. Fe3+(aq) + SCN-(aq) ⇄ Fe(SCN)2+(aq) yellow brown Adding Fe(NO3)3 increases the [Fe3+] and causes the reaction to shift right and turn brown. Adding KSCN increases the [SCN-] and causes the reaction to shift right and turn brown. Adding NaOH increases the [OH-] ,which reacts with Fe3+ , lowering the [Fe3+], causing the equilibrium to shift left , and turn yellow.