Question

(do all Parts)

Part A

What is the formula weight of lithium carbonate?

Express your answer to four significant figures and include the appropriate units.

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Part B

Find the total number of atoms in a sample of cocaine hydrochloride, C17H22ClNO4, of mass 23.5 mg .

N=

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Part C

Find the number of ibuprofen molecules in a tablet containing 160.0 mg of ibuprofen (C13H18O2).

Express your answer using four significant figures.

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A Freon leak in the air conditioning system of an older car releases 27 g of CF2Cl2 per month.

Part D What mass of chlorine is emitted into the atmosphere each year by this car? Express your answer using two significant figures. mCl = g

Answer 1

part-A

formula weight of lithium carbonate Li2CO3   = 2*7 + 1*12 + 3*16   = 74g/mole

part-B

mass of C17H22ClNO4    = 23.5mg = 23.5*10^-3 g

gram molar mass of C17H22ClNO4   = 339.8g/mole

no of moles C17H22ClNO4    = W/G.M.M

                                               = 23.5*10^-3/339.8   = 6.9*10^-5 moles

no of atoms of C17H22ClNO4   = no of moles * 6.023*10^23* atomicity                      { atomicity = total atoms in the molecule}

                                                       = 6.9*10^-5 *6.023*10^23*45 = 1.87*10^21atoms

part-C

no of moles of CH2Cl2   = 27/120.9   = 0.223 moles

1 mole of CH2Cl2 contains 2 mole of Cl

0.223 moles of CH2Cl2 contains 2*0.223 moles of Cl2

mass of Cl2 = no of moles * gram molar mass

                      =2* 0.223*35.5 = 15.84g