32) Home and Garden pH Indicators Beets Very basic solution changes from red to purple. Blueberries Blue pH 2.8-3.2. Turn red as
solution becomes more acidic. Cherries Red in acidic solution; turns blue/purple in basic solution. Curry Powder Curry's pigment curcumin changes from yellow at pH 7.4 to red at pH 8.6. Beet juice is added to a unknown solution and changes color from red to purple. Curry powder, added to the same solution, turns a deep red color. What can you tell about the hydrogen/hydroxide ion concentration of the unknown liquid?
Answer is: there are more hydroxide ions (OH⁻) in this unknown liquid than hydrogen ions (H⁺), because change of the the colors of curry powder and b<span>eet juice show that pH of unknown solution is higher than seven. </span>When pH is below 7, solution is
acidic, pH greater that 7 solution is basic and pH equals to 7, solution is
neutral. Concentration of OH⁻ ions is higher than H⁺ ions in basic solutions.
A buffer is defined as the mixture between weak acid and conjugate base. In the problem, acetic acid is the weak acid and sodium acetate the conjugate base.
When a strong acid as perchloric acid is added to a buffer, <em>the pH decreases slightly</em> because the acid reacts with conjugate base producing weak acid and not affecting directly the concentration of H⁺ ions.
