Question

Which has more molecules, a teaspoon of water that has a mass of 1.25 grams or a teaspoon of ethanol -C 2 H 5 OH that has a mass of 0.890 grams ?

Answer 1

Water

Step-by-step explanation:

To solve this problem, we need to solve for the number of molecules of these compounds;

given:

Mass of water = 1.25g

Mass of C₂H₅OH = 0.89g

We first solve for the number of moles of these compounds;

Number of moles =
`(mass)/(molar mass)`

Molar mass of H₂O = (2x1) + 16 = 18g/mole

Molar mass of C₂H₅OH = (12 x 2) + (1 x 5) + 16 + 1 = 46g/mole

Number of moles of H₂O =
`(1.25)/(18\\)` = 0.07moles

Number of moles of C₂H₅OH =
`(0.89)/(46)` = 0.02moles

We see that number of moles of water is more than that of ethanol. Therefore it has more molecules because;

1 mole of substance = 6.02 x 10²³

0.02moles of ethanol = 1.2 x 10²²molecules of ethanol

0.07moles of water = 4.2 x 10²² molecules of water