h�bbd``b`�$�� �� Observations (after the addition of both nitric acid and silver nitrate). Answers: 3, question: answers the answer is option a. When 44.2 g of KClO3 is completely decomposed, what is… Empirical Formula of Potassium Chlorate Purpose: To determine the empirical formula of potassium chlorate by decomposition into potassium chloride and oxygen, to write the balanced equation for this reaction, and to use stoichiometry to calculate the composition of an unknown mixture of potassium chlorate and potassium chloride. The potassium chlorate sample was not heated strongly or long enough. Use the balanced equation and your values of α (the mass of oxygen lost), β (the molar mass of oxygen) and δ (the molar mass of potassium chlorate) to determine the mass of potassium chlorate present in the original mixture (this is the KClO 3 that decomposed in this experiment and is represented by λ, below, in the equation.) ... Decomposition of Potassium Chlorate Last modified by: Administrator Company: Nitric acid spills may also be neutralized using the sodium bicarbonate solution by the sinks. The percent composition is calculated by Add a small amount of catalyst to a test tube. A common laboratory preparation of oxygen gas is the thermal decomposition of potassium chlorate (KClO3). Now heat the sample a second time for an additional 6 minutes using a high temperature flame. How long must the sample be heated the first time (total)? Be careful not to introduce any foreign material into the bottles of potassium chlorate since Answer In-Lab Questions #1 and #2 on page E4C-5. Using a Bunsen burner, heat the crucible and sample for a total of 12 minutes. Calculate the percent error between your average experimental value and theoretical value for the mass percent of oxygen in \(\ce{KClO3}\). Please refer to the table of solid substances and their properties in the Background section of the lab manual. endstream endobj 57 0 obj <> endobj 58 0 obj <> endobj 59 0 obj <>stream Which of the following sources of error could be used to explain this discrepancy (circle one)? :��ԇIe����|Y��|M��|�Wi��eU�?$% āDf�O�X�{�YcH������ a�U�P�E�[�H�\�_��1�,r#� Are there any other observations that you have made during this experiment (not those in the table above) that would suggest that the potassium chlorate was converted to a new substance upon heating? Procedure. 2. However, potassium chlorate can be dangerous and is hard to come by. The oxygen is driven off during the decomposition of potassium chlorate to produce potassium chloride. What will you observe if you obtain a positive test for chloride ions? Do you expect it weigh more than, less than or the same as the original potassium chlorate sample? The problem stated is the decomposition of potassium chlorate into potassium chloride and oxygen gas, so $$\ce{2KClO3 -> 2KCl + 3O2 ^}$$ Obviously, the half-reactions of this process can be written as the following: $$\ce{2Cl^5+ + 12e^- -> 2Cl^-}$$ $$\ce{6O^2- -> 3O2 + 12e^-}$$ Weigh 2.5 g of potassium chlorate(V) into each of the test tubes. Use the same balance for all weighings of the same sample 3. Be especially careful when using the Bunsen burner and handling hot equipment. What are. The Decomposition of Potassium Chlorate Hypothesis: Potassium chlorate decomposes into potassium chloride and oxygen gas, which means that when the glowing splint is inserted into the test tube, the flame will have enough fuel to fully reignite the splint. For the first 6 minutes, the sample should be, For the last 6 minutes, the sample should be. Upon analysis of this mixture, would you obtain a larger or smaller mass percent of oxygen than you would for an equal mass of pure sample of potassium chlorate (circle one)? Jessica Brown Chemistry Lab Write-up December 16, 2008 Decomposition of KClO 3 Purpose: To determine the value of the gas constant, R, by measuring the decomposition of potassium chlorate, KClO 3, using a liquid method. Specifically, the residue will be tested for the presence of chloride ions by the addition of nitric acid and aqueous silver nitrate. How many moles of KCIO3 are needed to produce 15 moles of oxygen gas? All compounds consist of elements chemically combined in fixed proportions – they obey the Law of Constant Composition. Using molar masses along with the known formula of potassium chlorate, calculate the theoretical mass percent of oxygen in \(\ce{KClO3}\). Legal. Clean both crucibles and their lids (obtained from the stockroom) by thoroughly rinsing with distilled water then drying as completely as possible with a paper towel. Larger Smaller. In Part A you will be performing several mass measurements. 32.7% d. 98.0% PLEASE GIVE A DETAILED DESCRIPTION OF HOW YOU FOUND THE ANSWER 72 0 obj <>/Filter/FlateDecode/ID[<2CBDB025D0504D4BB0269D9F7E621359>]/Index[56 31]/Info 55 0 R/Length 82/Prev 143198/Root 57 0 R/Size 87/Type/XRef/W[1 2 1]>>stream For more information contact us at info@libretexts.org or check out our status page at https://status.libretexts.org. Part B: Determination of the Stoichiometry of the Decomposition Reaction of Potassium Chlorate 1. To do this, the potassium chlorate must be heated to temperatures greater 400 °C, causing it to thermally decompose into potassium chloride and free oxygen: \[\ce{2KClO3 (s) ->[heat] 2KCl(s) + 3O2 (g)}\], \[\text{Potassium Chlorate} \ce{->} \text{Potassium Chloride} + \text{Oxygen}\]. The test tubes should be thoroughly cleaned and rinsed with distilled water. %%EOF 0 This can be theoretically calculated using atomic masses found on the periodic table, and experimentally calculated from lab data. Nothing was altered. Check that your lab safety goggles fit snugly around your eyes 2. Use your data to determine the experimental mass percent of oxygen in \(\ce{KClO3}\). In Part A of this lab, you will analyze a sample of potassium chlorate to determine the mass percent of oxygen present in it. ��L���00�=��*�b8�8�XE&y���@��*Lz>>� @� ��.q If a spill of either chemical occurs, rinse under running water and report the accident to your instructor. Higher/Lower. Write the word equation and the balanced formula equation for this decomposition reaction. Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. Then, once again, allow it to cool to room temperature. 1. LAB 5. Show your work clearly. Show your work clearly. Assuming complete decomposition, calculate the number of grams of O2 gas that can be obtained from 24.82 g KClO3. Introduction: The mass percentage of oxygen in potassium chlorate is determined by decomposing the potassium chlorate. In the on-campus lab, oxygen is prepared from the decomposition of potassium chlorate, an oxidizer mentioned above. In Part B of this lab, you will analyze the residue in left the "container" in order to experimentally verify its identity. What mass of oxygen should theoretically be released upon heating? 56 0 obj <> endobj Applying the Law of Mass Conservation, the difference in these measured masses is the mass of oxygen released (from the original potassium chlorate sample). We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. c) What is the volume of oxygen produced at STP? endstream endobj startxref In this lab we will observe the products of decomposition of potassium perchlorate (KClO4). 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