Question

What mass of carbon is present in 1.4*x10^20 molecules of sucrose?

Answer 1

No of moles of Carbon, C = mass/ molar mass.  
 Molar mass of carbon = 12.0107. We only have to calculate the no of moles
of carbon to obtain carbon's mass. .  
 From Sucrose chemical formula C12H22O11 we know that there are 12
carbon atoms. 
 So there are 1.4x10^(20) x12 = 16.8 x 10^20 carbon atoms. 
 We will use avogardo's number to find out the number of carbon molecules
in the compound. 
 From Avogadro's no. One mole of any substance equals to 6.022140857
atoms. 
 
 So X mole contains 16.8 * 10^(20) carbon atom 
 (16.8x10^20 carbon atoms)/6.022 x10^23 particles/mol = 0.00279 mols 
 The molar mass of carbon is 12.0107g/mol so we'll multiply to get the mass:
0.00279 mols x 12 = 0.03348.