When elements form compounds, the elements

When a septic tank backs up a goes in to clean it out

If anyone would be able to me out with these three questions it would be these are from the chem 2202 course.

You exhale co2 which is produced during cellular respiration.  co2 combines with the water in your blood's plasma to make up one half of the body's most important buffer pair, carbonic acid.  the more physical activity you engage in, the more co2 your body is producing.  you can see this by putting some of the cabbage indicator in a glass and then blowing bubbles into it through a straw.  can you see a change in the color of the indicator?