C172 PLT DECLARES EMER AFTER TURB ENCOUNTER AND VIOLATES ZZZ1 CLASS C AIRSPACE ON SUBSEQUENT FLT.

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WE WERE TRYING TO BEAT A COLD FRONT AND IT WAS NOT MOVING AS FORECAST. I KNEW WE HAD ONLY A CERTAIN AMOUNT OF TIME ON THE GND BEFORE THE SECOND BAND OF WX WOULD HIT. SO; I MOVED THINGS ALONG AS FAST AS I COULD. I WAS SURPRISED BY THE RAIN WHEN WE WERE FINALLY READY TO DEPART AND NOTED THE WINDS HAD SHIFTED 180 DEGS; FRONTAL PASSAGE. I RECHKED ALL AVAILABLE WX; FSS; AND RADAR BRIEFINGS. RADAR SHOWED GREEN TO ABOUT 30 MI S; THEN CLR ALL THE WAY TO MY DEST. I FILED IFR; GOT CLRED; ENCOUNTERED LIGHT TURB ON THE CLB; ENTERED THE BASES ON THE VECTOR TO THE AIRWAY; AND ALL HECK BROKE LOOSE. ON THE FIRST JOLT OF TURB; I TIGHTENED MY ALREADY TIGHT SEATBELT. THANKS TO BOTH ASRS AND MOUNTAIN FLYING CLINICS FOR THAT KNOWLEDGE. ON THE SECOND JOLT; I TIGHTENED THE SHOULDER HARNESS AS TIGHT AS IT WOULD GO. I ADVISED MY PLT-RATED PAX TO DO THE SAME. HE DID NOT. AFTER THAT; THE TURB WAS SO FAST AND HARD THAT I ADVISED ATC I WAS UNABLE TO MAINTAIN ALT. I WAS WATCHING THE ALTIMETER JUMP HUNDREDS OF FT IN BOTH DIRECTIONS. ATC CLRED ME FOR A BLOCK ALT OF A THOUSAND FT. THE JOLTS HAD EMPTIED MY PAX'S POCKETS SO THERE WAS A CELL PHONE AND PENS AND PAPERWORK FLYING THROUGH THE COCKPIT. THEN MY PAX HIT THE CEILING WITH HIS HEAD/HEADSET; HARD. THE PAX'S DOOR ALSO POPPED OPEN. MY HEADSET HIT THE SIDE WINDOW; AGAIN; AND AGAIN. WE TOOK ANOTHER HIT AND DROPPED 1000 FT. THE RADIO WAS CONSTANT CHATTER BUT ATC HAD JUST CALLED US; I RESPONDED 'MAYDAY MAYDAY MAYDAY; CESSNA NEEDS AN IMMEDIATE VECTOR TO ZZZ.' I KNOW MY STRESS LEVEL WAS EXTREMELY HIGH AS I DO NOT REMEMBER THE ENTIRE EXCHANGE OF COMS. I DO KNOW THAT I WAS USING ATC FULLY AND THE CTLR WAS VERY HELPFUL. IN ADDITION; THE OTHER PLTS ON FREQ KEPT THEIR SILENCE; WHICH REALLY HELPED. THE CTLR ISSUED A FEW LOW ALT ALERTS; BUT WE HAD DROPPED OUT OF THE BOTTOM OF THE CLOUDS INTO ABOUT 1/4 MI VISIBILITY; AND I WAS ABLE TO SPOT FAMILIAR LANDMARKS AND KNEW I COULD IGNORE MOST OF THE ALT ALERTS. THE TURB LESSENED; AND THE VISIBILITY IMPROVED. I LANDED AND CLOSED THE IFR FLT PLAN. MY PAX WAS SHAKEN BUT OKAY. BACK ON THE WX COMPUTER I SAW THE LITTLE DOCILE GREEN SPLOTCH HAD TURNED INTO A RED SPLOTCH SURROUNDED BY YELLOWS. WE WAITED OUT THE BAND OF WX; THEN WE HEADED OUT VFR WITH 10+ MI VISIBILITY. THE FLOOR OF ZZZ1 CLASS C AIRSPACE IS 2500 FT MSL. I CHOSE TO REMAIN AT 2200 FT SO AS TO NOT CROWD THE FLOOR OF ZZZ1 CLASS C; THEN CLB TO 2500 FT AND REMAIN BELOW THE CLOUDS AND ABOVE ALL OBSTACLES. LESS THAN 10 MINS AFTER DEP; I NOTICED WE WERE AT 2500 FT HEADED TO 2600 FT. I WAS 2700 FT BEFORE I GOT THE CLB STOPPED AND THE DSCNT STARTED AND STOPPED AT 2500 FT. THEN I REALIZED I WAS NOT OUT FROM UNDER ZZZ1 'C' AND I STILL HAD 3 MI TO GO. I CONTINUED THE DSCNT TO 2200 FT AND STAYED THERE UNTIL I WAS CLR OF THE AIRSPACE. ATC GAVE US DIRECT AND WE WERE ABLE TO COMPLETE THE FLT WITHOUT FURTHER INCIDENT.