Multiple choice

Which one of the following would have highest number of molecules?

  1. Ten grams of carbon dioxide

  2. Ten grams of oxygen

  3. Five grams of ammonia

  4. One gram of hydrogen
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The number of molecules in a given mass is inversely proportional to the molar mass. Hydrogen (H2) has the lowest molar mass (2 g/mol), so 1 gram of hydrogen contains the most molecules (0.5 moles). Carbon dioxide (44 g/mol), oxygen (32 g/mol), and ammonia (17 g/mol) all have higher molar masses, meaning the same mass contains fewer molecules. For example, 10g CO2 is only 0.23 moles.

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