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Fun with Stoichiometry: Humpty Dumpty Meets the Air Bag! Step 1: Humpty Dumpty sat on a wall, Humpty Dumpty had a great fall; All the King's horses, and all the King's men Could not put Humpty Dumpty together again. What if Humpty had an airbag? Design one for him and we'll have an egg drop contest! Your objective will be to create an airbag that will - allow Humpty Dumpty to survive the fall. In this activity you and your partner will design and test your own airbag system by combining baking soda (sodium hydrogen carbonate, also known as sodium bicarbonate, NaHCOs) and vinegar (acetic acid, CH3COOH) in recloseable sandwich bags. Carbon dioxide (CO2), water (H2O), and sodium acetate (NaCHsCOO) are the products of this reaction. Which product will be the gas that will inflate Humpty's airbag? Write the chemical equation for the reaction described above and then balance the equation. NaHC03 + CH3COOH * Step 2: A. You will test out the reaction by adding 1 gram of NaHC03 to 25 ml of vinegar in a re-cioseabie sandwich bag. 1. Wrap the sodium bicarbonate, NaHCOs, in a tissue before dropping it into the vinegar. This will allow you to control the reaction a bit. 2. Determine the best way to drop the wrapped NaHCOa into the vinegar in the bag without losing any gas. You will need to flatten the bag to remove air and seal the bag as quickly as possible. 3. Drop the NaHCOs into the vinegar and record your observations. 4. After the reaction becomes slow or stops, mix the ingredients to make sure the reaction is complete. 5. On separate paper, record your observations. B. Pay special attention to the inflation of the bag and think about how you could change this to make a better airbag. Step 3: A. Based on the first investigation, calculate the amounts of vinegar and baking soda you would need to react to fully inflate the bag and leave the least amount of left over reactants. In other words, what is the most CO2 you can generate to fill the bag, but not have it pop open and not have leftover reactants? The following information will be useful: r 1. You will need to get the volume of the bag. Create your own plan to do this. Describe it in your electronic report and record your measurements and volume. 2. Vinegar is a 1M solution of acetic acid (CH3COOH) in water. That means there is one mole of acetic acid in 1 liter of vinegar. The rest of the solution is water. If you use 25 ml, (0.025 liters) of vinegar, how many moles of acetic acid are you using? Step 4: Using your calculated values of NaHCOg and vinegar, test your hypotheses by experimentation to determine the best amounts of vinegar and baking soda to use in your airbag. Record all ideas, procedures, calculations and investigation results. You will need to turn all of this in with vour lab report. Take photos to include in your electronic report. Step 5: Once you determine how to make the most efficient air bag (efficient means using the least mass of chemicals to create the maximum carbon dioxide gas), design and build a vehicle for Humpty Dumpty (a raw egg) so that when he falls, the airbag will protect him. Humpty will be dropped from a height of 2 meters and he is depending on your design for survival/ The only materials you can use for the vehicle are: ® small cardboard box or large margarine tub • two ziplock plastic bags • 1M solution of acetic acid (vinegar) • Sodium hydrogen carbonate { sodium bicarbonate), NaHCOs (baking soda) • Tape PLEASE NOTE that we have found in previous years that the elaborate creation of a "vehicle" did NOT change our results in any way. As such, you will NOT need to spend time elaborately designing a vehicle. En Step 5, Once you determine how to make the most efficient air bag (using the least mass of reactants necessary), Humpty will be dropped from a height of 2 m. If you have calculated the amount of reactants properly, Humpty will survive. You can talk about this in your Discussion and/or Sources of error, if necessary. How-It Works Air bags flit with nitrogen gas as they deploy m automobile crashes. Hie source of the nitrogen gas is the chemical compound sodium azide (NaN3). Hazardoas sodium metal is produced along with the nitrogen/so potassium nitrate is added to con¬ vert the sodium into less hazardous sodimn oxMe {Na20')- iStolchion^etric calculations are needed to, determine the praise, quantity of sodimm aade that will produce the volurhe of nitrogen gas .xeqaired - •: to inflate the air bag. If too miicb'gas is produced; > die air bag may he so rigid that Mtting it w:ould be '; the same as hitting a solid wall. o Crash sensor detects. deceleration and sands signal to air bag module. HI Igniter explodes, heating sodium azide in the inftator. o Silicon dioxide (sand), sodium oxide, and potassium oxideformed in the inftalor fuse hito glass. Q Nitrogen gas inflates air bag. High temperature decomposes sodium azide into sodium and nitrogen gas. Sodium and potassium nitrate react releasing more nitrogen gas. ft#ft Jl s# *• •-ft ::.iv ;ft ft'ftr Thinking Critically f. Pradlcting Which stalling material usral in the air bag infiator is die least rmpoitant for he proper inflation of Hie air bag? Would it be necessary to have it present in a precise stoichiometric ratio? Why or why not? 2, Analyze and Conclude What is the sor- ; stoichioraetric ratio between Na!^ ¦ 'X : KN03 to ensare no sodium Is unraaeted? What would be the consequences of mi excess of KNOj to tlie operation of an Fun with Stoichiometry LAB REPORT REQUIREMENTS You will Carry out this lab on: Jan 18 / 19 and Jan 23 / 24 This lab report is due: Jan 30 / 31 It is the ONLY lab report you will be submitting for term 2, so do a thorough job! The Lab report will b® in TWO PARTS: PART ONE: (25 MARKS) There will be a group lab report (one per pair or trio - no groups larger than 3 are allowed). It may be easiest to submit this lab electronically as is does require photos to be included. Your group can decide on the best format (paper or electronic) to hand in part one. (1)TITLE/ FORMAT (1) Purpose Materials and Procedure do NOT have to be written out for (3) Observations (from Step 2A) (3) Data (Record and clearly report all relevant data from this CALCULATIONS: 1) Write the balanced chemical reaction (3 marks) 2) Show your calculation of the airbag volume (step 3) (3 marks) 3) Show your calculation of the number of moles of acetic acid in the 25 ml of vinegar (step 3) (3 marks) 4) Show your calculations (and explanations) of the amount of reactants needed to fill the airbag efficiently (step 4 and 5). This is where you would include your photos. (5 marks!!!) this lab lab activity). DISCUSSION (3 marks) Step 2B asks you to suggest changes to your airbag design. Do a thorough job of expanding on / explaining your suggestions as a group for full marks here. You might want to refer to some relevant theories in order to effectively explain your design change suggestions. PART TWO: (10 MARKS) The INDIVIDUAL portion of the lab report. You must do this section ON YOUR OWN and hand it in separately. This means that people in the same lab group may not get the same overall mark on their lab report. (1)TITLE/ FORMAT (6) EXTRA STOICHIOMETRY CALCULATIONS QUESTIONS: 1) Write the balanced chemical reaction between solid Magnesium and an aqueous solution of hydrochloric acid. Name this type of chemical reaction. 2) If 5.0 g of Mg (s) is reacted with as much acid is required, how many mL of Ha (g) will be formed at RTP? (3) SOURCES OF ERROR (from HUMPTY DUMPTY LABWORK): Suggest some sources of error associated with your group lab activity. Be sure to refer back to the Lab Report Format Handout, to ensure that you are completing this section correctly. Mrs. Toombs will look to see that you have come up with your OWN answers here, so do not just copy your partner's answers.