Rachel is given 50 grams each of three different white powders that look very similar. She is told that each of these powders is commonly used in cooking. Without tasting any of them, she is asked to try to identify them. She is told the amounts of sugar and salt that can each be dissolved in 100 mL of water.

Question

Substance Solubility
(g per 100 mL water)
table sugar 211
table salt 36
flour not soluble
Rachel adds all 50 grams of one powder to 100 mL of water and stirs it for a while. Afterwards, she has a clear liquid with some powder on the bottom.

Which of the following could this powder have been?
A.
flour
B.
sugar
C.
salt
D.
all of these

Answer 1

To determine which of the powders Rachel could be dealing with based on the information provided about solubility, we analyze each substance.

1. Table Sugar: The solubility of sugar (sucrose) in water is 211 grams per 100 mL. Since Rachel added only 50 grams of sugar to 100 mL of water, it would dissolve completely, resulting in no powder at the bottom.

2. Table Salt: The solubility of salt (sodium chloride) in water is 36 grams per 100 mL. Since Rachel added 50 grams of salt to 100 mL of water, this exceeds the solubility limit of salt. Therefore, not all the salt would dissolve, resulting in a clear liquid with some salt remaining at the bottom.

3. Flour: Flour is not soluble in water; if Rachel added 50 grams of flour to 100 mL of water, there would be a mixture of water and flour, but it would not dissolve, leaving a thick mixture and not a clear liquid.

Based on this analysis:

• If Rachel ends up with a clear liquid and some powder at the bottom, the most likely powder she could have used is table salt (C), since it's the only one that exceeds its solubility limit in this scenario and results in undissolved powder.

Therefore, the correct answer is C. salt.