Question

Scenario: You are testing two different household solutions with your cabbage indicator, using the color key to the right.

The second solution turns purple. A possible hydrogen ion concentration for this solution is:

1 × 10-2 M

7× 10-3 M

1 × 10-7 M

7 × 10-4 M
A cabbage p H indicator color key. Entries are 0 to 2, bright red; 3 to 4, pink; 5 to 6, purple; 7, dark violet; 8 to 9, blue; 10 to 11, bright green; 12 to 13, lighter green.

Answer 1

Purple on the key corresponds to pH 5–6, so [H+] is between 1 × 10^-6 and 1 × 10^-5 M.

None of the given choices fall in that range:
- 1 × 10^-2 M → pH 2
- 7 × 10^-3 M → pH ≈ 2.15
- 1 × 10^-7 M → pH 7
- 7 × 10^-4 M → pH ≈ 3.15

So no choice is correct. (If the intended option was 7 × 10^-6 M, that would be correct for purple.)