The koala bear dines exclusively on eucalyptus leaves. Its digestive system deto

Question

The koala bear dines exclusively on eucalyptus leaves. Its digestive system detoxifies the eucalyptus oil, a poison toother animals. The chief constituent in eucalyptus oil is asubstance called eucalyptol, which contains 77.87 percent C, 11.76percent H, and the remainder O. (a) What is the empirical formula for this substance? (b) A mass spectrum of eucalyptol shows a peak at about 154amu. What is the molecular formula of the substance? The koala bear dines exclusively on eucalyptus leaves. Its digestive system detoxifies the eucalyptus oil, a poison toother animals. The chief constituent in eucalyptus oil is asubstance called eucalyptol, which contains 77.87 percent C, 11.76percent H, and the remainder O. (a) What is the empirical formula for this substance? (b) A mass spectrum of eucalyptol shows a peak at about 154amu. What is the molecular formula of the substance?

Explanation / Answer

a) percent of carbon = 77.87      percent of hydrogen = 11.76 percent of oxygen       =100- (77.87 + 11.76 )                                      = 10.37                       C                         H                       O mass (g)         77.87                 11.76                 10.37 moles (n)       77.87 /12.01     11.76 /1.008          10.37 /15.999                        6.483                11.666                   0.648 All are divided by least factor                       6.483 / 0.648       11.666 /0.648        0.648 / 0.648                            10.00                   18.00                      1.00      Therefore empirical formula of eucalyptol is C10H18 O . ------------------------------------------------------------------- b) Molecular formula ofthe  eucalyptol   = empirical formula * n(moles)                                                                 = ( C10H18 O ) * n                     A mass spectrum of eucalyptol shows a peak at about 154 amu so themolamass of eucalyptol is 154 amu          and empirical formula mass = 154 amu [( 12*10) amu +(18*1 ) amu +(16*1)amu ].              so moles n = molarmass of C10H18 O /empirical formula mass                                = 154 amu /154 amu                                = 1          molecular formula of substance ,eucalyptol    = (C10H18 O ) * 1                                                                                 = C10H18 O                  

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