Which of the following is NOT an example of a solution?

• A. Air (a mixture of gases)
• B. Sand and water mixture
• C. Salt water (NaCl dissolved in H2O)
• D. Brass (an alloy of copper and zinc)

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the definition of a solution. A solution is a homogeneous mixture where the composition is uniform throughout, and the solute is completely dissolved in the solvent.
2. Step 2: Analyze each option to determine if it fits the definition of a solution:
3. - Air is a homogeneous mixture of gases, so it is a solution.
4. - Salt water is a homogeneous mixture where salt (NaCl) is dissolved in water, so it is a solution.
5. - Brass is a homogeneous alloy of copper and zinc, so it is a solution.
6. - Sand and water mixture is heterogeneous because sand particles do not dissolve in water and the mixture is not uniform.