a mixture of kcl and kclo3 has a mass of 2.565grams. The mixture is heated and t
ID: 506154 • Letter: A
Question
a mixture of kcl and kclo3 has a mass of 2.565grams. The mixture is heated and the Kclo3 is decomposed. After cooling,its mass is found to be 1.987 grams. perform each of the following calculations and show all work. Course/section Chum 13l lenani nstructor PRE-LAB ASSIGNMENT I. A mixture of KCI a mass of 2.565 grams. The mixture is KCIO3 is and KCIO3 has the heated an decomposed. After cooling, its massis foul to be 1.987 grams. Perform each of the following calculations and show all work. (a) Calculate the mass of oxygen lost from the mixture. (b) Calculate the number of moles ofor lost from the mixture. (c) Calculate the number of moles of KClos in the original mixture. (d) Calculate the mass of KCIO3 in the original mixture. (e) Calculate the percentage of KCIO3 in the original mixture 93Explanation / Answer
#1. Balanced reaction: 2 KClO3 --heat----> 2 KCl(s) + 3O2(g)
Stoichiometry: Upon heating, 2 moles of KClO3 produces 2 moles of KCl and liberates 3 moles of O2.
#2. Loss in Mass = Initial mass – Mass after drying
= 2.565 g – 1.987 g
= 0.578 g
The only chemical species escaping the sample during heating is O2. Thus, mass of O2 produced during heating is equal to the loss of mass during heating.
So,
Mass of CO2 produced = 0.578 g
Moles of O2 = Mass/ Molar mass
= 0.578 g/ (32.0 g/ mol)
= 0.0180625 mol
#3. See the stoichiometry of balanced reaction- 2 moles of KClO3 produces 3 moles of O2.
So, moles of KClO3 in sample = (2/ 3) x moles of O2
= (2/3) x 0.0180625 moles
= 0.012 mol
Mass of KClO3 in sample = Moles x Molar Mass
= 0.012 mol x (122.55 g/ mol)
= 1.47 g
% KClO3 in sample = (Mass of KClO3 / Initial mass of sample) x 100
= (1.47 g/ 2.565 g) x 100
= 57.31 %
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