Compound Y is a hydrocarbon that contains 85.7% carbon by mass. The diagram shows mass spectrum of compound Y Determine molecular formula of Y?

Answer 1

I gets...#C_6H_12# as the molecular formula....

We know that the hydrocarbon is #85.7%# by mass carbon. And so we address the empirical formula by assuming an #100*g# mass of the unknown compound...

#"Moles of carbon"=(85.7*g)/(12.01*g*mol^-1)=7.14*mol#

#"Moles of carbon"=(14.3*g)/(1.00794*g*mol^-1)=14.2*mol#..

Now clearly the empirical formula is #C_((7.14*mol)/(7.14*mol))H_((14.2*mol)/(7.14*mol))-=CH_2#

But the molecular formula is a whole number of the empirical formula....and this is....

#(CH_2)_n=84*g*mol^-1=nxx(12.011+2xx1.00794)*g*mol^-1#...

#n=(84*g*mol^-1)/(14*g*mol^-1)=6#...

And so our molecular formula is #6xxCH_2=C_6H_12#...

Good question!

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.