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The empirical formula of styrene is CH; its molar mass is 104.1 g/mol. What is the molecular formula of styrene?

AC2H4
BC8H8
CC10H12
DC6H6
Enone of these

i got C8H8 because i did

MWEF=n


but it says the answer should be C2H4


how is that possible?

Verified Answer :

Hagrid

You got the answer correct. If you would double check
given:C (12 g/mol) H (1 g/mol). 

12(8) + 1(8) = 104 g/mol

and for C2H4
12(2)+1(4) = 28g/mol

Also, chemical formula of styrene is C6H5CH=CH2.
  1. Find the molecular formula of styrene 

    Molecular formula = n x empirical formula 

    n= 104.14/13.02 = 8 where 13.02 is the empirical mass of CH 

    Molecular formula = CH x 8 
    = C8H8 

    2. From step 1, one molecule of styrene contains 8 atoms of hydrogen or one mole of styrene molecules contains 8 moles of hydrogen atoms (remember the formula of styrene is C8H8). 

    3. Convert 3.49 g styrene to mole styrene 

    mole styrene = 3.49 g/104.14 g/mol = 4.71 x 10^-3 mole 

    4. Calculate mole of hydrogens equivalent to 4.71 x 10^-3 mole styrene. Use mole ratio from step 2. 

    mole H = 4.71 x 10^-3 mole styrene 8 moles H/1 mole styrene 

    mole H = 0.0377 mole 

    5. Find number of H atoms contained in 0.0377 mole of hydrogen atoms. Use Avogadro's number. 

    no. of H atoms = 0.0377 mole H     6.02 x 10^23 atoms H/1mole H 

    no. of H atoms = 2.27 x 10^22 atoms H

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