Question

composition of potassium chlorate questions and problems

REPORT FOR EXPERIMENT 9 (continued) B. Qualitative Examination of Residue 1. Record what you observed when silver nitrate was added to the following: (a) Potassium chloride solution (b) Potassium chlorate solution (c) Residue solution 2. (a) What evidence did you observe that would lead you to believe that the residue was potassium chloride? (b) What would happen if you added silver nitrate to a solution of sodium chloride? Explain your answer. e) Did the evidence obtained in the silver nitrate tests of the three solutions prove conclusively that the residue actuallywas potassium chloride? Explain? QUESTIONS AND PROBLEMS 1. A student forgot to read the label on the jar carefully and put potassium chloride in the crucible instead of potassium chlorate. How would the results turn out? 2. What if a potassium chlorate sample is contaminated with KCI. Would the experimental % oxygen be higher or lower than the theoretical % oxygen? Explain your answer. 3. What if a potassium chlorate sample is contaminated with moisture. Would an analysis show the experimental % oxygen higher or lower than the theoretical% oxygen? Explain your answer? 4. Calculate the percentage of Cl in Al(CIO) 5. Other metal chlorates when heated show behavior similar to that of potassium chlorate yielding metal chlorides and oxygen. Write the balanced formula equation for the reaction to be expected when calcium chlorate, Ca(CIO)2 is heated.

Answer 1

Answer: Part B.

1. a) When silver nitrate was added to potassium chloride, a white precipitate of silver chloride is formed which in insoluble in water.

AgNO₃ + KCl -> AgCl (white ppt) +KNO₃

_b) When silver nitrate is reacted with potassium chlorate, no white precipitate of AgCl is formed

AgNO₃ + KClO₃ -> Ag(ClO₃) + KNO₃

c and 2 a) When silver nitrate is added to the residue then also we observed formation of white precipitate which indicates formation of AgCl. Therefore, it can be concluded that the residue contains potassium chloride.

Answer 2 b) If silver nitrate is added to the solution of sodium chloride then also the reaction occurs which leads to the formation of white AgCl which is insoluble in water.

AgNO₃ + NaCl -> AgCl + NaNO₃

Answer 2 c) The residue is actually potassium chloride as it forms a white precipitate on reaction with silver nitrate. If the residue is potassium chlorate then the reaction doesn't occur to furnish AgCl. The formation of silver chloride is a clear proof that the residue contain potassium chloride.

Questions and Problems

Answer 1: If the student put potassium chloride instead of potassium chlorate the reaction which is suppose to be oxidation turns out to be reduction as KCl is reducing agent. Therefore, it the student is trying to oxidize something, it undergoes reduction. The crucible when heated with potassium chloride in it would result in melting of the species.

Answer 2: The % oxygen in experiment is lower as there is no oxygen in KCl and due to contamination of potassium chlorate with KCl there will be less KClO₃ in experiment.

Answer 3: If potassium chlorate sample is contaminated with moisture then there will be higher experimental % oxygen as there is more oxygen in sample.

Answer 4: Molecular weight of all elements

Al = 27

Cl = 35.5 (3 x Cl = 106.5)

O = 16 (9 x O = 144)

Total mass 27 + 106.5 +144 = 277.5

Cl = 106.5/277.5 x 100 = 38.37 %

Answer 5:

Ca(ClO₃)_{2 ->}  CaCl₂ + 3O₂