Acids, Bases, and pH Buffers

The strong acid and strong base used in this lab are the same concentration. Thus, the magnitude of the pH change caused by addition of a single drop will be the same on wither side of the starting pH. Addition of acid lessens the pH, and addition of base raises the pH. In the graph below, negative drops indicate the magnitude of drops of acid, whereas positive drops indicate the magnitude of drops of base. What trends in the buffers ability to maintain a constant pH do you observe in the graph? B. The buffer was able to keep pH changes small for a large number of drops, but past a critical point the pH changed dramatically.

B. The buffer was able to keep pH changes small for a large number of drops, but past a critical point the pH changed dramatically.

Which color did the bromothymol blue indicator turn when it was added to the test tube containing citric acid? B. Yellow

A. Red B. Yellow C. colorless D. blue

Which of the following is the strongest base? C. ammonia

A. all three are of equal strength B. diluted bleach C. ammonia D. acetone

After addition of bromothymol blue, what was the pH of the test tube containing water? C. 7.00

A. 7.52 B. 1.30 C. 7.00 D. 6.56

Suppose you are given an unknown solution and you need to test its pH. The pH meter is broken, and all you have is the indicator bromothymol blue to use. You add two drops of bromothymol blue to 10mL of your unknown, and the solution turns a bright yellow. Which of the following is the best estimate of the pH of the unknown solution? D. 1.5

A. 8.5 B. 7.0 C. 11.5 D. 1.5

What is the biological significance of buffers? A. Buffers prevent even the slightest changes in pH that can inhibit important biological molecules such as enzymes.

A. Buffers prevent even the slightest changes in pH that can inhibit important biological molecules such as enzymes. B. Buffers prevent acidic or basic foods from altering the pH of the digestive system C. all of the answer choices are examples of the biological significance of buffers D. Buffers prevent stomach acids from escaping the stomach and digesting other tissues in the body.

Which of the following is true regarding how weak acid-conjugate base buffers neutralize acids and bases? A. The weak acid in the buffer neutralizes bases. The conjugate base neutralizes acids

A. The weak acid in the buffer neutralizes bases. The conjugate base neutralizes acids B. The conjugate base neutralizes bases. The weak acid neutralizes acids. C. The weak acid in the buffer is attracted to strong acids and surrounds them, neutralizing them. Conjugate bases act in a similar fashion on strong bases. D. strong acid and weak acid bond, forming a compound that is not acidic. A similar reaction occurs when a strong base is added to a buffer.

Suppose you forget to write down the contents of four test tubes/ Each contains a different solution that has a different pH. What is the best way to quickly identify the contents of each test tube? B. check the pH of each solution with a pH meter

A. add hydrocholoric acid to each solution, then check the pH with a meter B. check the pH of each solution with a pH meter C. check the pH of each solution with the thymol blue D. add sodium hydroxide to each solution, then check the pH with a meter

Which of the following has the solutions you tested correctly ranked from acidic to basic? B. Citric acid, acetone, diluted bleach

A. ammonia, acetone, water B. Citric acid, acetone, diluted bleach C. citric acid, ammonia, water D. acetone, diluted bleach, citric acid

In the Phosphate Buffer System Experiment, which solution had the least change in pH after addition of the acid or the base? A. mix of sodium dibasic phosphate and sodium monobasic phosphate

A. mix of sodium dibasic phosphate and sodium monobasic phosphate B. sodium dibasic phosphate C. sodium monobasic phosphate D. water

Which of the four solutions is the best buffer against addition of acid or base? A. sodium dibasic phosphate and sodium monobasic phosphate

A. sodium dibasic phosphate and sodium monobasic phosphate B. sodium dibasic phosphate C. sodium monobasic phosphate D. water

Which of the following is the strongest acid? C. citric acid

all three are of equal strength vinegar citric acid acetone

In the Phosphate Buffer System Experiment, which solution had the greatest change in pH after the addition of hydrochloric acid? D. water

sodium dibasic phosphate sodium dibasic phosphate + sodium monobasic phosphate sodium monobasic phosphate water

In the Phosphate Buffer System Experiment, which solution had the greatest change in pH after the addition of sodium hydroxide? C. water

sodium monobasic phosphate sodium dibasic phosphate + sodium monobasic phosphate water sodium dibasic phosphate