Calculations With  Information - Question #3    Answers

Given the following information:
The phenomenon known as "knocking" in an internal combustion engine depends markedly on the nature of the constituent hydrocarbons in gasoline.  The knocking tendency of a fuel is expressed in terms of an octane number.  The octane rating of a gasoline product may be greatly improved by the addition of small amounts of tetraethyllead (TEL), sometimes referred to as tetraethylplumbate or lead tetraethyl. This antiknock agent controls the concentration of free radicals and prevents premature explosions in the combustion chamber.

Tetraethyllead is a colourless, oily liquid with a faint fruity odor whose vapours form explosive mixtures with air.  It burns with an orange-coloured flame with a green margin.  Tetraethyllead has a specific gravity of 1.653 and boils at 200oC with decomposition.

The vapors are very toxic and fatal lead poisoning by ingestion, vapor inhalation, or skin absorption may occur.  Open-cup flash-point is 120oC.

The formula for tetraethyllead is given as: (C2H5)4Pb

The structural formula is:     C2H5
                                                |
                                  C2H--Pb-- C2H5
                                                |
                                               C2H5

Find the following:

a)  Mass of molecular mass of tetraethyl lead                              ____ g/mol

b)  Percent composition by mass                                                    ____ %C

                                                                                                         ____ %H

                                                                                                         ____ %Pb

c)  Number of atoms in 1 molecule of compound                            ____

d)  Number of molecules in 1 mole of compound                            ____

e)  Mass of 1 molecule of compound                                              ____ g

f)  Number of moles in 98.75 g of compound                                  ____ mol

g) Number of  grams in 0.625 moles of the compound                   _____  g