Help with a lab. I need to report the percentage of potassium chlorate in the un

Question

Help with a lab. I need to report the percentage of potassium chlorate in the unknown. I also need to find mass, moles, percent, and average.

ve su Percentage of KCIO3 in a Mixture Your instructor will provide you with approximately 8 grams of an unknown mixture of potassium chlorate and a stable salt (sodium chloride). Your assignment is to report the percentage of potassium chlorate in the unknown. Since the decomposition of two moles of potassium chlorate yields three moles of oxygen molecules, one can determine the number of moles of potassium chlorate in a mixture by measuring the number of moles of oxygen molecules released by the decomposition. And since the molecular weight of KCIOs can be calculated from its formula, the mass of potassium chlorate in the mixture is readily calculated. 2KCIO3 (s) KCl (s) + 102 (g) (Balance this please) ure: Caution: Since mixtures of KCIOs and combustible materials can explode violently upon heating, take the following precaution to be sure that your sample can be heated safely. Perform the following after r. Place the uncovered crucible on a ring stand If the small sample melts quietly and shows no evidence of you have read the introductory paragraph and have secured the sample from your instructo about 0.1 grams of the KCIOs mixture in a crucible, support with a clay triangle, then heat strongly. combustion or explosion, proceed as directed below with the remainder of your sample. Clean your crucible and lid, heat over a burner, cool, and then weigh. Add your sample (between 1 and 2 grams) to the crucible and reweigh. Record this mass. Heat until the sample melts or until the reaction appears to be complete, and then continue heating another five minutes. Lift the lid every couple of minutes to allow the oxygen to escape. Allow the crucible and lid to cool to room temperature (with the lid on) and weigh. Record this mass. Reheat strongly for another five minutes, cool, and reweigh. Record this mass. If the two weights are not within 0.005 grams (5 milligrams) of each other, repeat the heating and cooling procedure Repeat the above procedure with another sample. One can test intermittently for oxygen with a glowing splint. What will the splint do and what will it tell us about the completeness of the reaction? Caution: A dangerous explosion may result if the splint is dropped onto the hot KCIOs in the original mixture. he The student's grade on this experiment will be determined (1) by the accuracy of the results and (2) by the proper use of calculations. times as possible one neds For best results, it is desirable to carry out the experiment as many renc

Explanation / Answer

Trial 1

Trial 2

Trial 3

Mass of crucible, lid and sample (g)

24.022

24.461

23.029

Mass of crucible and lid (g)

22.188

22.626

21.256

Sample Mass (g)

1.834

1.835

1.773

Mass of crucible, lid and sample after first heating (g)

22.190

22.495

21.244

Subsequent masses after additional heating (g)

23.933

24.295

22.924

Subsequent masses after additional heating (g)

23.932

24.292

22.922

Final mass of crucible, lid and sample (g)

23.932

24.292

22.922

Mass of oxygen evolved (g) = (mass of crucible, lid and sample) – (final mass of crucible, lid and sample)

0.09

0.169

0.107

Moles of oxygen evolved (mole) = (mass of oxygen evolved)/(molar mass of oxygen)

Molar mass of oxygen = 32 g/mol

(0.09)/32 = 0.0028125

0.00528125

0.00334375

Moles of potassium chlorate in sample (mole) = (moles of oxygen evolved)*(2 mole potassium chlorate)/(3 mole oxygen)

(0.0028125)*(2/3) = 0.001875

(0.00528125)*(2/3) = 0.003521

(0.00334375)*(2/3) = 0.002229

Mass of potassium chlorate in sample (g) = (moles of potassium chlorate)*(molar mass of potassium chlorate)

Molar mass of potassium chlorate = 122.55 g/mol

(0.001875)*(122.55) = 0.2298

(0.003521)*(122.55) = 0.4315

(0.002229)*(122.55) = 0.2732

Mass of sodium chloride in sample (g) = (sample mass) – (mass of potassium chlorate)

1.834 – 0.2298 = 1.6042

1.835 – 0.4315 = 1.4035

1.773 – 0.2732 = 1.4998

Percent of potassium chlorate in sample (%) = (mass of potassium chlorate)/(sample mass)*100

(0.2298)/(1.834)*100 = 12.53

(0.4315)/(1.835)*100 = 23.51

(0.2732)/(1.773)*100 = 15.41

Average percent of potassium chlorate in sample

1/3*(12.53 + 23.51 + 15.41) = 17.15

Trial 1

Trial 2

Trial 3

Mass of crucible, lid and sample (g)

24.022

24.461

23.029

Mass of crucible and lid (g)

22.188

22.626

21.256

Sample Mass (g)

1.834

1.835

1.773

Mass of crucible, lid and sample after first heating (g)

22.190

22.495

21.244

Subsequent masses after additional heating (g)

23.933

24.295

22.924

Subsequent masses after additional heating (g)

23.932

24.292

22.922

Final mass of crucible, lid and sample (g)

23.932

24.292

22.922

Mass of oxygen evolved (g) = (mass of crucible, lid and sample) – (final mass of crucible, lid and sample)

0.09

0.169

0.107

Moles of oxygen evolved (mole) = (mass of oxygen evolved)/(molar mass of oxygen)

Molar mass of oxygen = 32 g/mol

(0.09)/32 = 0.0028125

0.00528125

0.00334375

Moles of potassium chlorate in sample (mole) = (moles of oxygen evolved)*(2 mole potassium chlorate)/(3 mole oxygen)

(0.0028125)*(2/3) = 0.001875

(0.00528125)*(2/3) = 0.003521

(0.00334375)*(2/3) = 0.002229

Mass of potassium chlorate in sample (g) = (moles of potassium chlorate)*(molar mass of potassium chlorate)

Molar mass of potassium chlorate = 122.55 g/mol

(0.001875)*(122.55) = 0.2298

(0.003521)*(122.55) = 0.4315

(0.002229)*(122.55) = 0.2732

Mass of sodium chloride in sample (g) = (sample mass) – (mass of potassium chlorate)

1.834 – 0.2298 = 1.6042

1.835 – 0.4315 = 1.4035

1.773 – 0.2732 = 1.4998

Percent of potassium chlorate in sample (%) = (mass of potassium chlorate)/(sample mass)*100

(0.2298)/(1.834)*100 = 12.53

(0.4315)/(1.835)*100 = 23.51

(0.2732)/(1.773)*100 = 15.41

Average percent of potassium chlorate in sample

1/3*(12.53 + 23.51 + 15.41) = 17.15

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