Question

Consider separate samples of water and carbon dioxide, each with the same mass. Which contains the greater number of molecules?

Answer 1

Answer: The sample that contains the greater number of molecules is water.

Explanation: To calculate the number of molecules, it is used the Avogadro's number (
`6.02*10^(23)` particles/molecules). So, considering that the mass to water and carbon dioxide is 1g (it can be any other number), the relationship between moles and molar weight is:

`moles =(mass)/(molar weight)`

To water:
`moles = (1g)/(18 g/mol)` = 0.05 moles.

Therefore,

1 mol ----
`6.02*10^(23)` molecules

0.05 moles ---- x

x =
`0.30*10^(23)` molecules of water.

To carbon dioxide:
`moles = (1g)/(44 g/mol)` = 0.02 moles.

Therefore,

1 mol ----
`6.02*10^(23)` molecules

0.02 moles ---- y

y =
`0.12*10^(23)` molecules of carbon dioxide.