Question

Chromate ions react according to the following equation, where the left side of the reaction is yellow and the right side is orange.

CrO2−4+2H+⇌Cr2O2−7+H2O

A student adds sodium hydroxide (NaOH
) to the solution at equilibrium. In one to two sentences, describe and explain any changes to the solution that the student will observe.

(2 points)

Short Answer Rubric (2 points)
Points Awarded Criteria
2
The answer is very clear.

The answer is fully supported by details.

There may be a few errors in grammar, usage, or mechanics. Errors do not interfere with meaning.

1
The answer is somewhat clear.

Details are weak or not related.

There are some errors in grammar, usage, and mechanics. Errors interfere with meaning.

0
The question is not answered.

Answer 1

OH− from NaOH reacts with H+ (OH− + H+ → H2O), lowering [H+]. By Le Chatelier’s principle the equilibrium shifts left, converting orange Cr2O7^2− to yellow CrO4^2−, so the solution becomes more yellow.