Question

Scoring Scheme: 3-3-2-1 Part V. The chemical system containing the simultaneous equilibria involves the precipitation of calcium oxalate in the presence of a weak diprotic acid, oxalic acid: Ca2+(aq) + C2042-(aq) ; CaC204(s) H2C204(aq) H20()FH30* (aq) HC204 (aq) HC204(aq)+ H20)H3(aq)+ C2042(aq) You added 10 drops of 6 M HCI to the solution of calcium chloride and oxalic acid. Which of the following statements explains your observations? a. The addition of H30t shifts the oxalic acid equilibria to the left, decreasing the oxalate ion concentration. Removing some of the oxalate ion from the calcium oxalate equilibrium causes the solid calcium oxalate to dissolve as this equilibrium shifts to the left. b. The addition of H30* shifts the oxalic acid equilibria to the left, decreasing the oxalate ion concentration. Removing some of the oxalate ion from the calcium oxalate equilibrium causes more calcium oxalate to precipitate as this equilibrium shifts to right. c. The addition of H3O* shifts the oxalic acid equilibria to the right, increasing the oxalate ion concentration. Increasing the oxalate ion concentration in the calcium oxalate equilibrium causes the solid calcium oxalate to dissolve as this equilibrium shifts to the left. d. The addition of H30 shifts the oxalic acid equilibria to the right, increasing the oxalate ion concentration. Increasing the oxalate ion concentration in the calcium oxalate equilibrium causes more calcium oxalate to precipitate as this equilibrium shifts to the right. o e. None of the above.

Answer 1

2 2. This xhale ttcabeplaines b Le.chateie s up a o drops M is added to the solution oralic aeid o Le -chateiers primuple, the equilibrium iu sht m that side, he inn i side the amount Thus, dussoiatin oxalic acid deireares and onatic acid equiu bria ttot et.be caune in ight to ft amounH ot deereare s becauva e ơn This results oxalate lơn,

2-t Previou ona ผe explained that the con centrahm oxalate iom de exeapes due to additin f tHhyo1 acoding to Le-chatelien HİU shift orr that, by gong σ v nhí ch side the cor, e n bation primtip Le-uhatelierors the eq1w li brium, |γ) wple, o calate ion ine reares So the equili bium wiu shitt to the left and lissoves resullin im an imtreane Soticl ealium oxalate - con Len tanti m 6,1 ox a late , on . Statemen The addi tim sht the ox a ie cid equilibria to the lejt, decrearimg the oxalate ion concemtation Removing some t the oxalate ion tom the Cad erwmv oxalate efter li brium caus e s the solid c서 coum oxalate to dissolve this epuuu brium shists to the lef t