E.23 Calculations

[605988349]

Hi,

Can anyone tell me what I'm doing wrong in my calculations for E.23 (textbook problems). "Calculate the amount (in moles) of (b) SO3 molecules in 7.00 x 10^2 mg of SO3."

This is what I have:
1S--> 32.065 g/mol
3O--> 48 g/mol
molar mass of SO3--> 80.065 g/mol

and because we are using 7.00 x 10^mg in mg, to convert it to grams it'll be 0.007.

: 0.007g x (1mol/80.065 g) = 8.743 x 10^5 mol SO3

However, in the answer sheet, it comes out as 8.74 x 10^-3 mol SO3.

Is there somewhere I messed up? Any help is appreciated :)

[chloe lee]

Hi,

all your calculations are right, except for your conversion of 7.00 x 10^2 mg to g. I think you forgot to include the 10^2 because 7.00 x 10^2 mg of SO3 is 7.00 x 10^2 mg / 10^3 which is equal to 0.70 g.

so, 0.70 g SO3 x (1mol/80.065 g) = 8.743 x 10^3 mol SO3

hope this helps