Red cabbage contains a water-soluble pigment. In a highly acidic solution, the pigment turns bright red, and in a moderately acidic solution, it turns pinkish. In a highly basic solution, the pigment turns yellow, and in a moderately basic solution, it turns bluish.

Question

A student makes a pH indicator from red cabbage that has a reddish-purple color with a pH of approximately 7. The student pours the same amount of the cabbage solution into each of four different beakers. He then adds a different household solution to each of the four beakers until a color change is obtained. His results are shown in the table below.
The student finds the following chart online from someone else’s cabbage pH indicator investigation.
Based on the information in the passage, which household solution has the highest pH?

a
club soda
b
lemon juice
c
drain cleaner
d
window cleaner

Answer 1

Based on the information provided about the color changes of the red cabbage pigment at different pH levels:

• In a highly acidic solution, the pigment turns bright red (indicating a low pH).
• In a moderately acidic solution, it turns pinkish (indicating a slightly higher, but still acidic, pH).
• In a highly basic solution, it turns yellow (indicating a high pH).
• In a moderately basic solution, it turns bluish (indicating a less extreme but still basic pH).

Given the household solutions listed:

a) Club soda - Generally mildly acidic (around pH 5 to 6). b) Lemon juice - Highly acidic (around pH 2 to 3). c) Drain cleaner - Very basic (typically pH 13 to 14). d) Window cleaner - Moderately basic (usually around pH 9 to 11).

From this information, we can determine that the household solution with the highest pH is:

c) drain cleaner.

It is the most alkaline option among the listed household solutions.