Question

A student finds two unlabeled flasks of clear liquids. One is believed to be 0.1 m nacl and the other to be 0.1 m naclo3. What is a quick way of determining what is in each flask?

Answer 1

Answer:

• Add AgNO₃ solution to both unlabeled flasks: based on solubility rules, you can predict that when you add AgNO₃ to the NaCl solution, you will obtain AgCl precipitate, while no precipitate will be formed from the NaClO₃ solution.

Explanation:

1. Adding AgNO₃ to NaCl solution:

• AgNO₃ (aq) + NaCl (aq) → AgCl (s) + NaNO₃ (aq)

2. Adding AgNO₃ to NaClO₃ solution

• AgNO₃ (aq) + NaClO₃ (aq) → AgClO₃ (aq) + NaNO₃ (aq)

3. Relevant solubility rules for the problem.

• Although most salts containing Cl⁻ are soluble, AgCl is a remarkable exception and is insoluble.

• All chlorates are soluble, so AgClO₃ is soluble.

• Salts containing nitrate ion (NO₃⁻) are generally soluble and NaNO₃ is not an exception to this rule. In fact, NaNO₃ is very well known to be soluble.

Hence, when you add AgNO₃ to the NaCl solution the AgCl formed will precipitate, and when you add the same salt (AgNO₃) to the AgClO₃ solution both formed salts AgClO₃ and NaNO₃ are soluble.

Then, the precipiate will permit to conclude which flask contains AgCl.