Practice Compound in Chemistry

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

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Quick 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 component elements.

Elements joined together to make something new with different properties.

Showing a random 20 of 50 problems.

Example 1

medium
How is CO different from CO2_2, and what does the existence of both show?

Example 2

hard
A 50 g sample of a binary compound contains 40 g of element A and 10 g of element B. Another 100 g sample of the same compound must contain how much of A?

Example 3

easy
Classify: ammonia gas (NH3_3).

Example 4

hard
Hydrogen peroxide (H2O2\text{H}_2\text{O}_2) and water (H2O\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.

Example 5

medium
What evidence shows that water has different properties from hydrogen and oxygen separately?

Example 6

hard
Suggest a single experimental test that distinguishes a compound from a mixture.

Example 7

medium
Hydrogen and oxygen gases are mixed but not reacted. Compound or mixture? Then they are ignited. Now what?

Example 8

medium
Classify each: (a) diamond, (b) carbon monoxide, (c) saltwater, (d) sugar.

Example 9

medium
Why is steel (iron + carbon) called a mixture rather than a compound?

Example 10

medium
Sugar dissolved in water and table salt dissolved in water look the same. Are both mixtures, both compounds, or different?

Example 11

medium
What is the formula for the compound made of one calcium ion (Ca2+^{2+}) and chloride ions (Cl−^-)?

Example 12

challenge
A 100 g compound is decomposed into 40 g of element X and 60 g of element Y. Another sample of the same compound is 25 g total. Predict the mass of X.

Example 13

hard
Why is the formula H2_2O2_2 different from H2_2O even though both have only H and O?

Example 14

medium
Why does H2O\text{H}_2\text{O} behave nothing like hydrogen gas or oxygen gas?

Example 15

medium
Classify each as an element, compound, or mixture: (a) table salt (NaCl), (b) oxygen gas (O2\text{O}_2), (c) bronze (Cu/Sn alloy), (d) carbon dioxide (CO2\text{CO}_2).

Example 16

hard
A compound is 75% C and 25% H by mass. Find its empirical formula (use atomic masses C = 12, H = 1).

Example 17

medium
Write the formula of the compound containing Al3+^{3+} and O2−^{2-}.

Example 18

hard
A pure white solid melts at exactly 801°C and is broken by electrolysis into a silvery metal and a green-yellow gas. Classify the solid.

Example 19

medium
Is brass (copper + zinc) a compound? Why or why not?

Example 20

medium
Bronze is an alloy of copper and tin. Is bronze a compound? Justify.
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