Question

which of the following is not a mixture? a ocean water b milk c brass d ammonia

Explanation:

• Ocean water: It contains water, salts (like sodium chloride), dissolved gases (such as oxygen and carbon dioxide), and other impurities. So, it is a mixture.
• Milk: It is a colloid (a type of mixture). It contains water, fats, proteins, lactose (a sugar), and minerals.
• Brass: It is an alloy (a solid - mixture). Brass is made by combining copper and zinc.
• Ammonia (\(NH_3\)): It is a compound. A compound has a fixed chemical composition. Ammonia is composed of nitrogen and hydrogen atoms chemically bonded in a \(1:3\) ratio (\(N: H\)). Compounds are not mixtures as mixtures have physically combined substances.

Answer:

d. Ammonia