Question

which of the following substances can have variable composition? view available hint(s) diamond graphite water air

Explanation:

• Diamond is a pure form of carbon (\(C\)). Its composition is fixed as it consists only of carbon atoms arranged in a specific lattice structure.
• Graphite is also a pure form of carbon (\(C\)). It has a different lattice structure than diamond but is still a pure element with a fixed composition.
• Water has a chemical formula \(H_2O\). For pure water, the ratio of hydrogen to oxygen is always \(2:1\) by atoms, so its composition is fixed.
• Air is a mixture. It mainly contains nitrogen (\(N_2\)), oxygen (\(O_2\)), carbon - dioxide (\(CO_2\)), noble gases, etc. The proportion of these components can vary. For example, in a closed room with people breathing, the concentration of \(CO_2\) will increase over time, and in different geographical locations (such as at high altitudes), the proportion of oxygen in the air is different.

Answer:

air