8/18/2019 Exercise 13-Percent Composition and Molecular Formula

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PERCENT COMPOSITION

PURPOSE: Finding the percentage by mass of oxygen released by the decomposition of hydrogen peroxide.

MAER!A"S:

# $ %& cm test t'bes MnO#  matches goggles

% $ small bea(er )* sol'tion of +#O#  balance splint

SAFE,:

%. -ear safety goggles at all times. #. o not ingest chemicals. ). o not to'ch chemicals.

PRO/EURE: O0SER1A!O2S:

A. Place t3o %&4centimeter test t'bes in a small bea(er.

0. Place the bea(er on a balance. A. mass of bea(er 5 test t'bes 6 777777 g/. Record the mass of the bea(er and test t'bes in the

obser8ations col'mn 9label 3hat yo' are recording and

incl'de 'nits.

CAUTION:  -ear safety goggles 3hen doing this acti8ity.. Add manganese dioxide 9MnO# to a depth of abo't

% cm to one of the test t'bes.

E. etermine the mass of the bea(er; test t'bes; andmanganese dioxide on the balance. 0. mass of bea(er 5 test t'bes 5 MnO# 

F. Record the mass in the obser8ations col'mn 9label 3hat 6 777777777 g

yo' are recording and incl'de 'nits.

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/A"/U"A!O2S:

%. /alc'late the amo'nt of hydrogen peroxide 'sed in this experiment then m'ltiply that amo'nt by )*. his

is the mass of hydrogen peroxide 'sed. 9Use the information in yo'r obser8ations letters / and 0.

#. /alc'late the mass of oxygen released d'ring the reaction 9basically s'btract the total masses before and

after the reaction of bea(er and test t'bes.

). From the res'lts of this experiment; find the percentage of oxygen released from hydrogen peroxide 'sing

the ans3ers from ?% and ?# and the percent composition form'la. 9%@ >'dos for calc'lating this correctly.

Percent /omposition and Molec'lar Form'la -or(sheet

%. -hats the empirical form'la of a molec'le containing B&.&* carbon; &.&* hydrogen; and #C.@*

oxygenD

#. !f the molar mass of the compo'nd in problem % is %%@ gramsmole; 3hats the molec'lar form'laD

). -hats the empirical form'la of a molec'le containing %.G* lithi'm; %B.)* carbon; and B&.@*

oxygenD

H. !f the molar mass of the compo'nd in problem ) is G). gramsmole; 3hats the molec'lar form'laD

Write the molecular formulas of the following compounds:

&. A compo'nd 3ith an empirical form'la of /#O+H and a molar mass of grams per mole.

B. A compo'nd 3ith an empirical form'la of /H+HO and a molar mass of %)B grams per mole.

G. A compo'nd 3ith an empirical form'la of /F0rO and a molar mass of #&H.G grams per mole.

. A compo'nd 3ith an empirical form'la of /#+ 2 and a molar mass of HB grams per mole.

 Answer the following questions:

C. he percentage composition of acetic acid is fo'nd to be )C.C* /; B.G* +; and &).H* O. etermine the

empirical form'la of acetic acid.

%@. he molar mass for I'estion ?C 3as determined by experiment to be B@.@ gmol. -hat is the molec'larform'laD

%%. Aniline; a starting material for 'rethane plastic foams; consists of /; +; and 2. /omb'stion of s'ch

compo'nds yields /O#; +#O; and 2# as prod'cts. !f the comb'stion of C.G% g of aniline yields B.B) g+#O and %.HB g 2#; 3hat is its empirical form'laD

%#. he molar mass of aniline is C) gmol. -hat is its molec'lar form'laD

%). /alc'late the mass percent of carbon; nitrogen and oxygen in acetamide; /#+& 2O.

%H. A &@.&% g sample of a compo'nd made from phosphor's and chlorine is decomposed. Analysis of the prod'cts sho3ed that %%.)C g of phosphor's atoms 3ere prod'ced. -hat is the empirical form'la of the

compo'ndD

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%&. -hen #.&@@@ g of an oxide of merc'ry; 9+gxOy is decomposed into the elements by heating; #.H@& g of

merc'ry are prod'ced. /alc'late the empirical form'la.