Compound Examples in Chemistry

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Compound.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Chemistry.

Concept Recap

A pure substance composed of two or more different elements chemically bonded together in a fixed ratio, whose properties differ entirely from those of its constituent elements and can only be separated by chemical means.

Elements joined together to make something new with different properties.

Read the full concept explanation →

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Compounds have fixed proportions and properties different from their elements.

Common stuck point: A compound is different from a mixture—compounds are chemically bonded.

Sense of Study hint: When identifying whether a substance is a compound, check two things. First determine if it contains two or more different elements (if only one element, it is an element, not a compound). Then check if the elements are chemically bonded in fixed ratios (if just mixed physically, it is a mixture). Finally, verify that the substance has different properties from its component elements.

Worked Examples

Example 1

easy
Define a compound and explain how it differs from both an element and a mixture.

Solution

  1. 1
    A compound is a pure substance composed of two or more different elements chemically bonded in a fixed ratio.
  2. 2
    Unlike an element, a compound contains more than one type of atom. Unlike a mixture, a compound has a definite composition that cannot vary.
  3. 3
    Compounds can only be separated into their elements by chemical means (e.g., electrolysis), not by physical means like filtering or distilling.

Answer

\text{Compound: fixed ratio, chemically bonded, two or more elements}
The law of definite proportions states that a compound always contains the same elements in the same proportions by mass, regardless of the source or method of preparation.

Example 2

medium
Water (\text{H}_2\text{O}) is a compound that can be decomposed by electrolysis. Write the equation for this decomposition and explain why the products have different properties from water.

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

medium
Classify each as an element, compound, or mixture: (a) table salt (NaCl), (b) oxygen gas (\text{O}_2), (c) bronze (Cu/Sn alloy), (d) carbon dioxide (\text{CO}_2).

Example 2

hard
Hydrogen peroxide (\text{H}_2\text{O}_2) and water (\text{H}_2\text{O}) both contain hydrogen and oxygen. Explain why they are different compounds with different properties, even though they contain the same elements.
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Related Concepts

ElementMoleculeMixture

Background Knowledge

These ideas may be useful before you work through the harder examples.

elementmolecule