Practice Molecule in Chemistry

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

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Quick Recap

The smallest unit of a covalent substance, consisting of two or more atoms held together by chemical bonds (typically covalent), acting as a single distinct unit.

Atoms stuck together. Water (H2O) is one molecule with 3 atoms.

Showing a random 20 of 50 problems.

Example 1

easy
Does NaCl exist as discrete molecules?

Example 2

easy
Sucrose has the formula C12H22O11. How many atoms are in one molecule of sucrose?

Example 3

easy
Is argon (Ar) found in air a molecule or a single atom?

Example 4

hard
Compare diamond and a sample of CO2. Both contain carbon. Which sample is composed of molecules?

Example 5

medium
A student sees P4 as a label for white phosphorus. Is P4 a molecule? Explain.

Example 6

easy
Define a molecule and explain the difference between a molecule of an element and a molecule of a compound.

Example 7

medium
Explain why O2 and O3 (ozone) are both molecules of the same element but have different properties.

Example 8

medium
How many atoms are in one molecule of C6H12O6 (glucose)? How many molecules are in 1 mole of glucose?

Example 9

medium
Ammonia is NH3. How many atoms are in 3 molecules of ammonia?

Example 10

hard
A sample contains 1.20×1024 molecules of H2O. How many moles of water and how many total atoms are in the sample?

Example 11

hard
A label says 'one molecule of KOH.' Is the label scientifically accurate? Justify.

Example 12

easy
What type of bond typically holds the atoms in a molecule together?

Example 13

challenge
Classify each sample as (i) a discrete molecule, (ii) a noble-gas atom, (iii) an ionic formula unit, or (iv) a network solid: S8, CaF2, SiO2 (quartz), Kr.

Example 14

hard
Ethylene glycol is C2H6O2. What is the total number of atoms in 0.40 mol of ethylene glycol?

Example 15

easy
How many atoms are in one molecule of carbon dioxide, CO2?

Example 16

medium
How many molecules are in 0.25 mol of CO2?

Example 17

medium
How many hydrogen atoms are in 5 molecules of ammonia, NH3?

Example 18

hard
A molecule of aspirin has the formula C9H8O4. Calculate the total number of atoms in one molecule, the molar mass, and the number of hydrogen atoms in 0.50 mol of aspirin.

Example 19

easy
Is O2 (oxygen gas) a molecule? Explain in one line.

Example 20

challenge
Classify each as molecular element, molecular compound, or neither: O2, CO2, Ne, NaCl.
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