How many molecules are in 10.8 grams of #C_12H_22O_11#?

1 Answer
Nov 12, 2015

Answer:

#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#