Aspirin (acetyl salicylic acid) is a weak acid with the chemical formula HC9H7O4. The solubility of aspirin is 4.6 g per 1.00 L solution, and a saturated solution of aspirin has a pH of 2.56. Write the expression (chemical equation) that describes the saturated solution.

HC₉H₇O₄(aq) + H₂O(l) ⇄ C₉H₇O₄⁻(aq) + H₃O⁺(aq)

Explanation:

A weak acid as aspirin, HC₉H₇O₄, is in equilibrium with water as follows:

This is the chemical equation that describes the process.

As you can see, not all aspirin is dissolved, just a part that is converted in its conjugate base (A weak acid doesn't dissociate completely!).

Also, the pH is decreasing because the hydronium ion (H₃O⁺) is produced in the equilibrium (Remember, if you have an increasing in H₃O⁺ concentration the pH will decreases and vice versa).

water at room temperature is flowing through a pipe with pressure taps located 10 ft apart along one section of the pipe, which are connected to a mercury (s=13.6) manometer.