How many molecules are in 10.8 grams of C_12H_22O_11?

1 Answer
Nov 12, 2015

1.901 xx 10^22

Explanation:

The question is how many molecules are in a determined amount of an specific compound.

First step to obtain the number of moles, that is the mass/MW

"no. of moles" = "mass"/"molar mass"

The MW in this case is the sum of the atomic weights of the different atoms in the composition of the compound.

For this specific case it is C_12H_22O_11, is possible for a fast calculation to use the integer weights for C, H and O, 12, 1 and 16 respectively.

Then MW = 12(12) + 22(1) + 11(16) = "342 g/mol"

moles = "mass"/"MW" = ("10.8 g"/"342 g/mol") = "0.03157 moles"

The number of molecules per mol is defined by the Avogadro's number 6.0221409 xx 10^23,

Giving up the numer of molecules as

0.03157 xx 6.022 xx 10^23 = 1.901 xx 10^22