Lab - Composition of Potassium Chlorate

Lab 3 Assignment Report Composition of Potassium Chlorate Title: Composition of Potassium Chlorate Date: Name: Objective: In lab 3 the composition of potassium chlorate was determined by heating the compound and releasing the oxygen. Introduction: A compound is composed of two or more elements held together by chemical bonds. To determine the composition of a compound by calculating the total mass due to each element. This can be calculated by using the atomic mass of each element. Pre-laboratory Questions: Pre - Lab Answer the following. 1) _____Percent Composition__ of a compound is the percentage by mass of each element in the compound.. 2) ___Formula Mass___ ____ of a compound is determined by adding up the atomic masses of all the atoms making up the formula. 3) ___Molar Mass _____ of an element in a compound is determined by multiplying the atomic mass of that element by the number of atoms of that element in the formula. 4) Percentage composition = Mass of element / Molecular Mass X 100 Report Data: Mass of crucible cover: 15.984 g Mass of crucible + cover 36.185 g Mass of crucible + cover + KCIO 37.254 g Mass of crucible + cover + KCIO3 after 1st heating 37.207 g Mass of crucible + cover + KCIO3 after 2nd heating 37.202 g Mass of crucible + cover + KCIO3 after 3rd heating 37.201 g Mass of original sample 37.254 - 36.185 1.069 g Mass lost during heating (mass of oxygen) 37.254 - 37.201 0.053 g Final mass of residue (Mass of KCIO3). 37.202- 36.185 1.016 g Experimental % O in KCIO3 0.53 / 1.016 x 100 52.1 % Experimental % KCI in KCIO3. 1.016 / 1.063 x 100 95.58 % Theoretical % O in KCIO3 47.997 / 122.55 x 100 39.16% Theoretical % KCI in KCIO3. 74.55 / 122.55 x 100 Percent Error in Experimental % O determination 60.83 % -33.3% Recorded Observations from Chloride Ion Test Potassium Chloride Solution Cloudy Potassium Chlorate Solution No changes Residue in Crucible Solution Lightly cloudy at top Experiments: Measurements 1-5 were recorded after completing the following: The original mass of the crucible cover were measured and recorded. The Mass of the crucible and the cover were measured and recorded. After heating a crucible on a hot plate for 2 minutes using maximum heat, 1.063 g of potassium chlorate were directly added to the crucible after cooling. The covered crucible containing Potassium chlorate were then heated on low for 8 minutes. Directly after the crucible and potassium chlorate were heated on low for 10 minutes, removed from the hot plate and cooled for an additional 10 minutes. Once cooled for 10 minutes the first measurement for the mass of the crucible, cover and KCIO3 was recorded. These steps were then repeated 3 times to record a total of 3 mass mismeasurements of the crucible, cover and KCIO3. Measurements 6-8 were recorded using the recorded data from 1-5. Measurement 6 was recorded as the mass of the original sample of potassium chlorate. The measurement was recorded after calculating the difference of the mass of crucible, cover and KCIO3 from the mass of the crucible and over. Measurement 7 was recorded as the total mass lost during heating. Mass lost during heating was found by calculating the difference of the original mass of crucible, cover and KIO3 from the mass of crucible, cover and KCIO3 after the final heating was complete. Measurement 8 was recorded as the total mass of residue of KCIO3. Measurement 8 was recorded after calculating the difference the final mass of crucible, cover and KCIO3 after final heating from the initial mass of crucible and cover. Measurements 9-13 were recorded after completing experimental and theoretical formulas (listed on page 27) using original data found during experiment. Measurement 9 was recorded after calculating the experimental percent of O in KCIO. The total was sound by dividing the determined mass of oxygen by the determined mass of KCIO3 the multiplying by 100. Measurement 10 was recorded after calculating the experimental percent of KCI in KCIO. The total was found by dividing the determined mass of KCI by the determined mass of KCIO3 and multiplying by 100. Measurement 11 was recorded as the theoretical percent of oxygen in KCIO3.This measurement can be calculated by dividing the theoretical mass of oxygen by the molar mass of the chemical compound and multiplied by 100. Measurement 12 was recorded after calculating the theoretical percent of KCI in the compound KCIO3. This calculation was done by dividing the theoretical mass of KCI by the compounds molar mass and multiplying by 100. Final measurement wan recorded after calculating the percent error of the percentage of oxygen. This was done by subtracting the theoretical amount by the experimental oxygen amount dividing the sum by the theoretical total and multiplying by 100. Post Laboratory Questions: 1. Why was a white precipitate not formed upon adding silver nitrate to tube 2? There were no chloride ions in the solution. 2. What observation suggest that the residue left behind after heating was KCI? When KCIO3 is heated it releases the gas of oxygen leaving behind KCI. 3. What do you hypothesize would happen if you added silver nitrate to the solution of sodium chloride? A double replacement reaction where the positive and negative ions trade places. 4. Do the results from the silver nitrate test prove conclusively that the residue left behind after heating was KCI? If a white solid form that showed that there was chloride ions present. The white solid formed in the KCl and the residue but not the KClO3. Meaning that our residue was in fact potassium chloride. 5. If your original KCIO3 sample was contaminated with KCI, would you expect the experimental % oxygen to be high or lower than the theoretical % oxygen? The experimental % of oxygen would be lower because there would be more KCI in the sample than oxygen. 6. If your original KCIO3 sample was contaminated with moisture, would you expect the experimental % to be high or lower than the theoretical % oxygen? The theoretical value of oxygen in the sample contaminated with moisture because there is more oxygen in the sample.