What color does blue litmus paper turn when detecting ammonia?

The correct answer is that blue litmus paper turns red when it comes into contact with an acidic substance, not ammonia since ammonia is a basic substance. Therefore, blue litmus paper does not change its color when exposed to ammonia.

When ammonia is present, there is no reaction that would lead to a color change in blue litmus paper; it maintains its blue color, indicating that the environment is alkaline rather than acidic. This is crucial in identifying the presence of ammonia because a change in litmus color would suggest an entirely different chemical interaction.

In a typical acid-base reaction involving litmus paper, a clear understanding of the properties of acids and bases helps to properly interpret the results observed during experiments.