Lab 11 - Mandatory Lab assignment in class PDF

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Mandatory Lab assignment in class...

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Farzana Uddin Chem 101- Section 1L04 Experiment 11: Alka-Seltzer and the Escaping Gas Initial Observation: Vinegar is a clear liquid with strong smell, and Alka Seltzer tablet is white solid with no smell. Step 1: Measure the mass of a small beaker, then pour 30 mL of vinegar in it, and measure the beaker again. After measuring the beaker with the vinegar in it, subtract the initial mass from the new mass to get the mass of the vinegar. Step 2: Measure the mass of two Alka Seltzer tablets. Step 3: Measure the mass of a 600 mL beaker, then pour the 30 mL vinegar into it, and drop the two Alka Seltzer tablets into the beaker. Record observation. Step 4: When the reaction stops bubbling, and the gas escapes, measure the mass of the beaker with the mixture in it. Find the mass of CO2 of one Alka Seltzer tablet. Step 5: Repeat the experiment. Experimental Observations: When the Alka Seltzer tablets were being mixed with the vinegar, the reaction started to bubble, and it looked like sprite. It took a while for the bubbles to stop. In the following chart, the masses of everything is recorded: Item 600 mL beaker Vinegar 2 Alka Seltzer tablets Total Mass (Initial) After reaction Mixture + beaker Mixture only (final) Initial-Final=Mass of CO2/2 Calculations:

1st Trial Mass (g) 216.05 29.66 6.54 36.2

2nd Trial Mass (g) 177.3 23.99 6.4 30.39

1st Trial Mass (g) 249.67 33.62 1.29 g

2nd Trial Mass (g) 205.5 28.2 1.09

1st trial: To find mass of CO2 for one Alka Seltzer tablet: Total mass of vinegar, and 2 Alka Seltzer tablets= 36.2g After reaction: mass of mixture and beaker = 249.67g

Beaker mass with mixture – beaker mass = 33.62 g (Mixture mass) Initial mass (36.2) - Final Mass (33.62) = 2.58g (CO2 in two alka seltzer tablets) 2.58 g / 2 = mass of one tablet = 1.29 g --> 1290 mg 2nd trial To find mass of CO2 for one Alka Seltzer tablet: Total mass of vinegar, and 2 Alka Seltzer tablets= 30.39g After reaction: mass of mixture and beaker = 205.5 g Beaker mass with mixture – beaker mass = 28.2 g (Mixture mass) Initial mass (30.39) - Final Mass (28.2) = 2.19 g 2.19 g / 2 = mass of one tablet = 1.095 g --> 1095 mg Group 1 2 3 4 5 Avg: Mass of one tablet: 2.2/2 = 1.1g --> 1100 mg

Mass CO2 (g) of 2 tablets 2.2 2.32 1.65 2.42 2.09 2.2

Results/Conclusion: According to the group results, one commercial Alka Seltzer tablet contains 1.1 g of CO2. Using that information you can calculate the mass of NaHCO3 in one tablet: 1.1g CO2 x (1mol/44.0095g CO2) x (1 mol NaHCO3/ 1 mol CO2) x (84.008g NaHCO3/ 1 mol NaHCO3) = 2.099 g --> 2.1 g of NaHCO3 in one alka seltzer tablet --> 2099 mg Therefore Mr. Smiley's accusation is true that the Alka Seltzer tablet does not match the 1916 mg of NaHCO3 advertised. Post-Lab Answers: 1) We as a class settled on one value to report to the Bayer Corportation by reporting the avergae of our two results to the group, and then adding up every groups result and dividing that by the number of groups. That is how we got the value to report to the Bayer Corporation. 2. 27.37% Molar mass of NaHCO3 is (22.99g + 1.008g + 12.01g + 16.00g(3) = 84.008g) Molar mass of Na is (22.99g) The mass percent of Na ((22.99g / 84.008g)*100%) = 27.366 .% The mass percent of Na is 27.37%

3. 64.79 % Mass percent of NaHCO3 in one alka seltzer tablet : (2.1 g NaHCO3/ 3.241 g Alka Seltzer mass) x 100 = 64.79 % --> 65%...