ACR LINED UP FOR LNDG ON WRONG PARALLEL RWY AFTER BEING GIVEN A CHANGE IN RWY PLAN. ERROR DISCOVERED BY CREW AND CTLR.

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APCHING ORD FROM BEARZ; WE WERE GIVEN RWY 14R. AS WE APCHED ORD WE WERE GIVEN A RWY CHANGE. WE BOTH THOUGHT IT WAS RWY 22R WHEN; IN FACT; IT WAS RWY 22L. THEN WE WERE GIVEN A R TURN TO PARALLEL RWY 22 OUTBOUND. THEN APCH CTL ASKED US IF WE HAD THE FIELD IN SIGHT. WE SAID YES AND THEY CLRED US FOR A VISUAL APCH. WE TURNED L TO INTERCEPT RWY 22R AND AS WE WERE ON AN INTERCEPT HDG TO RWY 22R; WE SAW TWO ACFT ON FINAL. ONE WAS AHEAD OF US AND ONE WAS FURTHER OUT ON FINAL; BUT TOO CLOSE FOR US TO FIT INTO THE LINE. WE CALLED TWR TO CLARIFY THE RWY AND AT THE SAME TIME WE STARTED A L TURN AWAY FROM RWY 22R FINAL. TWR SAID OUR RWY WAS RWY 22L AND FOR US TO TURN L AND CLB TO 4000 FT; WHICH WE DID. WE CONTINUED TO CIRCLE AROUND AND LANDED ON RWY 22L. THE RWY ASSIGNMENT WAS RWY 22L; BUT WE HEARD RWY 22R. SUPPLEMENTAL INFO FROM ACN 442710: WE WERE INITIALLY TOLD EXPECT RWY 14R. OUR RWY ASSIGNMENT WAS THEN CHANGED TO RWY 22L. WE THOUGHT WE WERE GOING TO RWY 22R; THE MORE USUAL LNDG RWY. WE WERE TURNED ONTO A PARALLEL DOWNWIND FOR RWY 22 AND ASKED IF WE HAD THE FIELD IN SIGHT. WE RPTED THE FIELD IN SIGHT AND WERE CLRED FOR A VISUAL APCH AND PASSED TO ORD TWR. WE TURNED TO INTERCEPT RWY 22R AND SWITCHED TO TWR. TURNING THROUGH BASE APPROX 6 MI NE OF O'HARE WE SAW 2 OTHER ACFT ON FINAL (BOTH VISUALLY AND ON TCASII). ONE WAS JUST PAST RIDGE OM AND THE OTHER ABOUT 4 MI BEHIND. WE WOULD HAVE HAD TO FIT IN BTWN THEM IN THE SEQUENCE AND THERE WOULD NOT HAVE BEEN SUFFICIENT ROOM. WE QUERIED THE TWR WHEN WE CHKED IN IF WE WERE TO LAND RWY 22R. HE RESPONDED 'NO; RWY 22L.' SHORTLY AFTER THAT HE INSTRUCTED US TO TURN L TO 090 DEGS AND CLB TO 4000 FT. WE HAD ALREADY TURNED AWAY FROM RWY 22R FINAL BY THE TIME WE WERE INSTRUCTED TO GO AROUND. BOTH OF US THOUGHT THE RWY ASSIGNMENT WAS RWY 22R. I DON'T REMEMBER WHAT THE APCH CLRNC WAS; BUT WE WERE PROCEEDING TO RWY 22R UNTIL WE SAW THE OTHER TFC.