Which of the following tests can help distinguish between a mixture of baking soda and cornstarch and baking powder in a sample?

• A. Heat the sample; baking powder will melt, but baking soda and cornstarch will not.
• B. Add iodine solution; baking powder will turn blue-black, but baking soda and cornstarch will not.
• C. Add water; baking soda and cornstarch will dissolve completely, but baking powder will not.
• D. Add vinegar; baking soda will react vigorously, while baking powder will produce a slower reaction.

Answer: (D)

Verified step by step guidance

1. Understand the composition of each substance: baking soda is sodium bicarbonate (NaHCO\_3), cornstarch is a carbohydrate (a polysaccharide), and baking powder contains baking soda plus an acid and a filler like cornstarch.
2. Recognize that baking soda reacts with acids to produce carbon dioxide gas (CO\_2), which causes bubbling or fizzing, while cornstarch does not react with acids.
3. Note that baking powder contains both an acid and a base, so it reacts with water and acids but typically produces a slower or less vigorous reaction compared to pure baking soda.
4. Consider the test with vinegar (an acid): adding vinegar to baking soda will cause an immediate and vigorous release of CO\_2 gas, while baking powder will react more slowly due to its acid-base balance, and cornstarch will not react at all.
5. Conclude that the vinegar test is effective to distinguish between a mixture of baking soda and cornstarch (which will fizz vigorously) and baking powder (which will fizz slowly), making it the best choice among the options.