AP CHEMISTRY JUNE BOZEMAN #2

AP Chemistry BOZEMAN #2 Chemical Analysis                   Name:

15 points

1.  CH₂O is the empirical formula of what molecule?

2.  What is the molar mass of gold (give a unit!)?

3.  Notice that even though hydrogen and oxygen are diatomics, when dividing by the

            mass of each element to find moles, you only use 1 gram and 16 grams                             respectively.  What are the three steps in finding the empirical formula when        given a mass spectrum analysis?

a)

b)

c)

4.  SHOW WORK FOR POINTS IN THIS PROBLEM.  (10 points)

Nicotine is composed of C,H, and N.   A 5.250 mg sample of nicotine was combusted, producing 14.242 mg of CO₂ and 4.083 mg of H₂O. SIG FIGS COUNT!!!

HINT:  Don't worry about the mg - make them all grams.  It's all about the ratio, baby.

a)  What is the mass of CO₂?

b)  FInd the grams of carbon in the 14.242 g of CO₂ that is given:

c)   Change grams of C to grams to mols of C:

d)  What is the mass of H₂O?

e)  FInd the grams of hydrogen in the 4.083 g of H₂O that is given:

f)   Change grams of H to mols of H:

g)  All that is left is finding the nitrogen.  To do this, subtract the masses you got for the carbon (answer b) and the hydrogen (answer e) from the total number of grams        in the nicotine (given in the problem).  This is your grams of nitrogen.

h)  Convert your grams of nitrogen to moles of nitrogen.

i)  Divide by the smallest number of mols to find the mol ratio.  Show your work here:

j)  What is the empirical formula for nicotine?