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1. A 16.6g sample of sodium bicarbonate (NaHCO3) is decomposed by heating. How m

ID: 812215 • Letter: 1

Question

1. A 16.6g sample of sodium bicarbonate (NaHCO3) is decomposed by heating. How many grams of Na2CO3 remains? a. How many combined grams of CO2 and H2O in question 1? 2.. A 4.832g mixture of KClO3 and NaC1 is heated on a hot plate causing the decomposition to form KCl(s) and O2 (g). If 3.474 g of the mixture remains after complete decomposition: a. Calculate moles of O2 lost. b. Calculate the grams of KCIO3 present in the initial mixture. c. Calculate the percent composition of KClO3 in the mixture.

Explanation / Answer

1-NaHCO3----->Na2CO3 +CO2+H2O

2moleNaHCO3 gives 1mole Na2CO3

15.6/168                  15.6/336=0.04643mole Na2CO3&CO2&H2O

gm of Na2CO3=.04643x106=4.921gm

gm of CO2=0.04643x44=2.04292

gm of H2O=0.04643x18=0.83574total gm of CO2&H2O=2.87866gm

2-4.832gm mix KCl +NaCl

3.474gm remains only KClO3 decompose

1.358 gm KClO3 is present in the mix

a- 2 mole KClO3                 3mole O2

1.358/122.5moleKClO3          3/2x1.358/122.5=1.5x 0.011086=0.01663molex32=.53216gm O2

b-1.358 gm KClO3 is present in the mix

c- % composition=1.358/4.832x100=28.104%