ERJ-170 FLT CREW HAS A SPD DEV DURING ARR TO ORD FOLLOWING A LATE RWY CHANGE.

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WHEN APPROACHING ORD; WE WERE ASSIGNED RWY 22R. WHEN CHKING ON WITH A SECOND CTLR; WE WERE CONFIRMED RWY 22R AGAIN. A FEW MINUTES LATER; WE WERE CHANGED TO RWY 27R. WE WERE THEN GIVEN A 060 DEG HDG AFTER ORD VOR. AT APPROX 10000 FT MSL; ATC SAID; 'AS SOON AS YOU GET SLOWED DOWN; DSND AND MAINTAIN 7000 FT.' SHORTLY AFTER WE WERE CLRED TO 4000 FT; EXPECTING A SHORT APCH. WHEN GIVEN A 210 DEG HDG TO TURN BACK TOWARD FINAL; ATC ASKED WHAT OUR SPD WAS. FO STATED; '250 KTS.' ATC THEN SAID; 'YOU WERE GIVEN 210 KTS. TIGHTEN YOUR TURN.' WE INCREASED OUR BANK ANGLE. ATC THEN SAID; 'STOP DSCNT. DO YOU SEE COMPANY TFC ON FINAL FOR RWY 27L AT 12 O'CLOCK?' WE THEN REPORTED TFC IN SIGHT AND WERE CLRED FOR VISUAL RWY 27R. WE WERE NEVER GIVEN 210 KTS; AND IF WE WERE; IT WAS NEVER ACKNOWLEDGED BY READBACK AND ATC NEVER NOTICED. WE ARE CERTAIN 210 KTS WASN'T EVER ASSIGNED AND IF IT WAS; WHY DIDN'T ATC CATCH IT SOONER AND LET US DSND 6000 FT AT 250 KTS? ONLY ONE FMS (FO'S) WAS WORKING WHICH FURTHER INCREASED OUR WORKLOAD AFTER 2 RWY ASSIGNMENTS IN JUST A FEW MINUTES. ITS POSSIBLE 210 WAS ASSIGNED BUT NEVER ACKNOWLEDGED DUE TO AN OVERWHELMING AMOUNT OF REASSIGNMENTS; VECTORS; BRIEFINGS; AND CHKLISTS. ATC SHOULD'VE BETTER PLANNED OUR APCH AND NOT PRESSURED US INTO SUCH A TIGHT TURN NEAR PARALLEL TFC. ITS CLR THEY WERE HAVING LOTS OF TFC ISSUES AND PLACED THEIR BURDEN ON US AT LAST MINUTE. IF THEY DON'T HEAR 210 KTS READ BACK; THEY SHOULD DEMAND IT. IT'S IMPOSSIBLE TO SLOW TO A SPD YOU NEVER ACKNOWLEDGED.