You will observe an instructor place 5 mL of 0.01 M sodium hydrogen carbonate solution in a small beaker, then add 5 drops of m-cresol purple indicator. The instructor will use a straw to bubble the expired air from the lungs, through the solution until a change occurs. 1.What do you observe? (m-cresol is purple above pH 8, and yellow below pH 7). 2. What exhaled gas caused this change in pH? 3.What chemical reaction occurs in water with this gas? 4. What buffer system have you formed in this container? Give the formulas of the conjugate acid-base pair that comprise the buffer system.

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