Question

A certain anesthetic contains 64.9 percent carbon, 13.5 percent hydrogen, and 21.6 percent oxygen by mass. At 120°C and 750 mmHg, 1.00 L of the gaseous compound weighs 6.90 g. What is the molecular formula of the compound?

Answer 1

1) First you l have to calculate the empirical formula of the compound and the mass of the empirical formula.

2) Then with the information of the volume, temperature and pressure (PV=nRT) you can calculate the number of moles.

3) With the number of moles and the mass in 6.90g you can calculate the Molecular mass (MM= mass/ number of moles) .

4) You can divide the molecular mass by the empirical formula mass and find the factor that you have to multiply the empirical formula to obtain the molecular formula.

Answer 2

1) to calculate the empirical formula, convert the percentage in g, divide them by the atomic mass of the element (C=12, O=16, H=1), generate a pseudoformula. Cx Oy Hz Divide the 3 numbers (x,y,z) by the smallest one. Round the decimal of the other until get a whole number. You should get your empirical formula. Calculate the empirical mass of that formula.

Answer 3

2) and 3) can be combined in the formula

\[MM =\frac{ m RT }{ PV } \]

Answer 4

@Cuanchi sorry you lost me on this. How does this lead up to a molecular formula?

Answer 5

@Cuanchi Couldn't I just take the g/mole of each element combined them find the mole then divide that number into my empirical formula?

Answer 6

@Cuanchi
So for carbon I would take the C4 I got and divide by .0932 which is the moles and I end up with C43
Then I do the same thing with the others and I get the final molecular solution as
C43H107O11