Universal indicator solution is composed of a blend of molecules that elicit a color alteration upon encountering H+ and OH– ions. This solution is employed by scientists to estimate the pH of an unfamiliar substance. Analyze the chart provided to observe the array of pH levels identified by universal indicator solution and the colors they associate with.

Question

Red: ph: 1
Pink: ph: 2
Orange: ph: 3
Beige: ph: 4
Yellow: ph: 5
Lime-green: ph: 6
Green: ph: 7
Dark green: ph: 8
Turquoise: ph: 9
Pale blue: ph: 10
Blue: ph: 11
Dark blue: ph: 12
Violet: ph: 13
Purple: ph: 14
A nutritionist aims to investigate the influence of food combinations on stomach pH. She introduces ten drops of freshly extracted potato juice into a beaker containing a universal indicator solution. This action results in the solution turning yellow in color. Subsequently, she introduces ten drops of white vinegar, a solution of acetic acid.
Using the color chart for the universal indicator provided above, and considering a comprehension of acid-base chemistry, select the response that accurately predicts the PROBABLE color the universal indicator will exhibit when vinegar is introduced to potato juice.

Answer 1

To analyze the scenario, we look at the colors associated with the pH levels provided by the universal indicator.

1. Freshly Extracted Potato Juice: When the nutritionist introduced the potato juice, the universal indicator turned yellow, which corresponds to a pH level of 5. This indicates that the potato juice is acidic.

2. Introducing White Vinegar: White vinegar contains acetic acid, which is a weak acid. Acetic acid has a low pH, typically around 2-3. When vinegar is introduced to the already acidic potato juice (pH 5), it will likely further lower the pH.

When combining these two solutions, the resulting pH will be lower than 5, falling into the acidic range of the universal indicator. Given that vinegar is relatively strong compared to the potato juice, the final pH will likely be significantly lower than 5.

Referring back to the color chart:

• A pH of 4 corresponds to the color beige,
• A pH of 3 corresponds to the color orange,
• A pH of 2 corresponds to the color pink,
• A pH of 1 corresponds to the color red.

Since the vinegar is more acidic than the potato juice and will decrease the overall pH significantly, the most probable color for the universal indicator after introducing the vinegar is orange (pH 3) or potentially even pink (pH 2), depending on the exact mix.

However, considering a likely scenario without extreme concentrations, we can conservatively predict that the universal indicator will show an orange color, corresponding to a pH of about 3. Thus, the probable color the universal indicator solution will exhibit after the addition of vinegar is likely to be orange.