Which of the following mixtures is classified as a solution?

• A. Oil and vinegar
• B. Sand suspended in water
• C. Salt water (NaCl dissolved in H2O)
• D. Smoke in air

Answer: (C)

Verified step by step guidance

1. Understand the definition of a solution: A solution is a homogeneous mixture where the solute is completely dissolved in the solvent, resulting in a single phase with uniform composition throughout.
2. Analyze each mixture given: Oil and vinegar form a heterogeneous mixture (a suspension or emulsion) because oil and vinegar do not mix uniformly; they separate into layers.
3. Sand suspended in water is a heterogeneous mixture called a suspension because the sand particles do not dissolve and can settle out over time.
4. Salt water (NaCl dissolved in H2O) is a homogeneous mixture because the salt (solute) dissolves completely in water (solvent), forming a uniform single-phase solution.
5. Smoke in air is a heterogeneous mixture called a colloid or aerosol, where tiny solid particles are dispersed in a gas but not dissolved.