Solving Stoichiometry Problems

Transcription

1 Science Objectives Students will write ratios from balanced chemical equations. Students will use -to-mass conversion to determine mass of reactants and products iven the number of s. Students will calculate the number of s and the mass of a reactant or product when iven the number of s or the mass of another reactant or product usin the balanced chemical equations. Students will list the steps used in solvin stoichiometric problems. Vocabulary molar mass ratio combustion -to-mass conversion reactant mass-to- conversion product About the Lesson This lesson involves students usin a simulation of three combustion reactions to develop skills necessary to solve stoichiometric problems. Students will use the combustion of methane to analyze ratios in chemical reactions. Students will the use the combustion of propane to analyze to mass conversion. Finally, students will use the combustion of propane to analyze mass to conversion. As a result, students will: Reinforce the skills of balancin chemical equations Develop a method of solvin stoichiometry problems TI-Nspire Naviator Send out the Solvin_Stoichiometry_Problems.tns file. Monitor student proress usin Class Capture. Use Live Presenter to allow students to show how they manipulate variables that effect results. Activity Materials Compatible TI Technoloies: TI-Nspire CX Handhelds, Tech Tips: This activity includes screen Nspire CX handheld. It is also appropriate for use with the TI-Nspire family of products includin TI-Nspire software and TI-Nspire App. Sliht variations to these directions may be required if usin other technoloies besides the handheld. Watch for additional Tech Tips throuhout the activity for the specific technoloy you are usin. Access free tutorials at captures taken from the TI- ators/pd/us/online- Learnin/Tutorials Lesson Files: Student Activity Solvin_Stoichiometry_ Problems_Student.doc Solvin_Stoichiometry_ Problems _Student.pdf Solvin_Stoichiometry_ Problems.tns TI-Nspire Apps for ipad, TI-Nspire Software 013 Texas Instruments Incorporated 1 education.ti.com

2 Discussion Points and Possible Answers Have students answer all questions on their activity sheet. Move to pae 1.. Have students answer questions 1-11 before movin to pae 1.3. In this part of the activity students will analyze ratios. 1. Students are to read the directions on how to use the simulation. When finished, they can select to close the directions. If needed at any time durin the simulation, students can select b if they would like to view the directions aain. Tech Tip: To view the directions aain, students should select > Stoichiometric Problems > Directions. They may need to back-out to the main Tools Menu to see the desired menu option.. First students need to balance the equation usin the up and down arrows to adjust the coefficients that appear in front of each reactant and product. Q1. Record the balanced equation: Answer: CH 4 + O CO + H O 3. Select the up arrow to chane the number of s of methane to be used in the reaction. Then, select play. Q. Select four different amounts of methane. For each amount, record the s of reactants and products in the table below. Sample Answers: Moles of Methane Moles of Oxyen Moles of Carbon Dioxide Moles of Water Texas Instruments Incorporated education.ti.com

3 Q3. How many s of water are produced for 0.30 of methane? What is the ratio? Answer: 0.6 s of H O for 0.3 of CH 4 Q4. How many s of water are produced for every of methane? What is the ratio? Answer: s of H O for every of CH 4 Teacher Tip: Remind students that in this part of the activity they should use sinificant fiures for all calculations. Q5. How many s of water are produced for.0 s of methane? For any iven number of s of methane? Answer: 4.0 s of H O for.0 s of CH 4. Usin coefficients in the balanced equations, s HO Moles HO.0 s CH 4 = 4.0 s HO. For any iven number of s of 1 CH methane, use the ratio of water and methane as a conversion factor. 4 Q6. How many s of oxyen are consumed to produce 1.5 s of carbon dioxide? Answer: 3.0 s of O for 1.5 s of CO Q7. How many s of oxyen are consumed for every of carbon dioxide? Answer: s of O for every of CO Q8. How many s of oxyen are consumed to produce 3. of carbon dioxide? How many are consumed to produce any iven number of s of carbon dioxide? s O Answer: Moles O 3. s CO = 6.4 s O. To produce any iven number 1 CO of s of carbon dioxide, use the ratio of oxyen and carbon dioxide as a conversion factor. Q9. What do ratios tell us? Answer: The ratio provides the ratio of the s of one reactant or product to the s of another reactant or product in the balanced equation for a chemical reaction. Mole ratios are conversion factors that can be used to relate: 013 Texas Instruments Incorporated 3 education.ti.com

4 1. s of product formed from a certain number of s of reactant. s of reactant needed to form a certain number of s of a product. 3. the number of s of a particular reactant needed to completely react with a certain number of s of a second reactant. Q10. How do you calculate the ratios? Answer: The coefficients in a balanced chemical equation can be used to determine the relative number of s of a compound involved in a chemical reaction. Q11. Write all ratios for a iven reaction. 1 CH4 1 CH4 1 CH4 Answer: the followin ratios can be written:,,, s O 1 CO s H O 1 CH4 1 CH4 s O s O 1 CO,,,,, and the inverses of each of 1 CO s H O 1 CO s H O s H O these ratios. Teacher Tip: Encourae students to analyze each problem and determine what type of ratio they need to use in order to find unknown amounts of reactants or products. Move to pae 1.3. Have students answer questions 1-19 before movin to pae 1.3. In this part of the activity students will use the simulation to determine that to mass conversion is necessary to calculate the mass of products for a iven amount of reactants in s. They should use three sinificant fiures for all calculations in this part of the activity. 4. Students are to balance the iven equation. They can use the up and down arrows to adjust the coefficients that appear in front of each reactant and product. Q1. Record the balanced equation: Answer: C H 4 + 3O CO + H O 013 Texas Instruments Incorporated 4 education.ti.com

5 5. Students will now set the number of s of ethene equal to 1.00 and then select. Teacher Tip: Remind students that in this part of the activity they should use 3 sinificant fiures for all calculations. Q13. How many s of carbon dioxide will be produced in this reaction? Support your answer usin the appropriate ratio. s CO Answer: Moles CO 1.00 C H =.00 s CO 4 4 Q14. How many rams of carbon dioxide will be produced in this reaction? Support your answer usin the appropriate molar mass. Answer: molar mass of CO is = 44.0 /, s 44.0 / = 88.0 Q15. How many s of water will be produced in this reaction? Support your answer usin the appropriate ratio. s HO Answer: Moles HO 1.00 CH 4 =.00 s HO 4 Q16. How many rams of water will be produced in this reaction? Support your answer usin the appropriate molar mass. Answer: molar mass of H O is = 18.0 /, s 18.0 / = Texas Instruments Incorporated 5 education.ti.com

6 6. Students are to enter their calculated answers in the appropriate text boxes. If necessary, they should revise their calculations. 7. Then students will reset the simulation. They can select the up or down arrows to chane the number of s of ethene to be used in the reaction. Tech Tip: Students will need to tap in the rams box to brin up the keyboard to input answers. Press and hold down the key that hides the keyboard and choose split -- to see behind the keyboard. You can then use the same key to slide the split keyboard up and down. 7. Select three different amounts of ethene and calculate the s and the mass of the products. Show your calculations and results in the table below. Verify your calculations usin simulation. Sample Answers: Moles of C H Calculations s CO.00 s of C H 4.00 s of CO s of CO of CO s HO.00 s of CH s of HO s of HO of HO s CO 5.00 s of C H 10.0 s of CO s of CO of CO s HO 5.00 s of CH s of HO s of HO of HO s CO 8.00 s of C H 16.0 s of CO s of CO of CO Grams of CO Grams of H O Texas Instruments Incorporated 6 education.ti.com

7 s HO 8.00 s of CH s of HO s of HO of HO Q18. How many rams of water and carbon dioxide are produced if s of ethene is burned? Answer: Find the number of s of CO and H O usin appropriate ratios, and then use molar mass of each product to convert from s to mass. s CO s C H = 1.40 s CO 4 1 CH4, 1.40 s 44.0 / = 61.6 of CO s H O s C H = 1.40 s H O 4 1 CH4, 1.40 s 18.0 / = 5. of H O Q19. How many rams of water and carbon dioxide are produced if 4.00 s of oxyen is consumed? Answer: Find the number of s of CO and H O usin appropriate ratios, and then use molar mass to convert from s to mass. s CO 4.00 s O =.67 s CO 3 s O,.67 s 44.0 / = 118 of CO s H O 4.00 s O =.67 s O 3 s O,.67 s 18.0 / = 48.1 of O Tech Tip: Students can insert a Calculator pae to complete calculations for the problems by selectin /~ and selectin Add Calculator. They can also use the Scratchpad». Tech Tip: Students can insert a Calculator pae by selectin > Calculator. Move to pae 1.4. In this part of the activity students will use the simulation to calculate the mass of products iven the mass of reactants in the combustion of propane combustion reaction. They should use three sinificant fiures for all calculations in this part of the activity. Based on their work, they will determine the key steps to solvin stoichiometry problems. 013 Texas Instruments Incorporated 7 education.ti.com

8 8. First students are to balance the equation. Use the up and down arrows to adjust the coefficients that appear in front of each reactant and product. Q0. Record the balanced equation: Answer: C 3 H 8 + 5O 3CO + 4H O 9. Now students are to set the mass of propane equal to 10.0 and then select the play button. Teacher Tip: Remind students that in this part of the activity they should use 3 sinificant fiures for all calculations. Q1. How many s of propane are used in this reaction? Show your calculations. 1 Answer: 10.0 rams of C H 0.7 s of C H 44.1 rams Q. How many s of carbon dioxide will be produced in this reaction? Show your calculations. 3 s CO Answer: Moles CO 0.7 s C H = s CO 013 Texas Instruments Incorporated 8 education.ti.com

9 Q3. How many rams of carbon dioxide will be produced in this reaction? Show your calculations. Answer: s 44.0 / = 30.0 Q4. How many s of water will be produced in this reaction? Show your calculations. Answer: 4 s H O Moles H O 0.7 s C H = s H O 1 C3H8 Q5. How many rams of water will be produced in this reaction? Show your calculations. Answer: s 18.0 / = Students are to enter their calculated answers in the appropriate text boxes. If necessary, they should revise their calculations. 11. Then students will reset the simulation. They can select the up or down arrows to chane the mass of propane to be used in the reaction. Q6. Select two different values and calculate the s and mass of the products. Show your calculations and results in the table below. Verify your calculations usin the simulation. Grams of C 3 H Calculations rams of C H s of C H 44.1 rams 3 s CO s C H.040 s of CO.040 s of CO of CO 4 s HO s of C3H8.7 s of HO.7 s of HO of HO Grams Grams of CO of H O Texas Instruments Incorporated 9 education.ti.com

10 rams of C H 1.13 s of C H 44.1 rams 3 s CO 1.13 s of C H 3.39 s of CO 3.39 s of CO of CO 4 s HO 1.13 s of C3H8 4.5 s of HO 4.5 s of HO of HO Q7. How many rams of water and carbon dioxide are produced if 5.0 rams of propane is burned? Answer: Use propane s molar mass to find the number of s of propane used in the reaction. Find the number of s CO and H O usin appropriate ratios, and then use the molar mass of each product to convert from s to mass rams of C H s of C H 44.1 rams 3 s CO s of C H = 1.70 s of CO 1 C3H s 44.0 / = 74.8 of CO 4 s H O s of C H =.7 s of H O 1 CH4.7 s 18.0 / = 40.9 of H O 013 Texas Instruments Incorporated 10 education.ti.com

11 Q8. How many rams of propane and oxyen were used if it resulted in 50.0 rams of water? Answer: Use water molar mass to find the number of s of water produced in the reaction. Find the number of s C 3 H 8 and O usin appropriate ratios, and then use the molar mass of each reactant to convert from s to mass rams of HO.78 s of HO 18.0 rams 1 C3H8.78 s of H O = s of C H 4 s H O s of C 3 H / = 30.6 of C 3 H 8. 5 s O.78 s of H O = 3.48 s of O 4 s HO 3.48 s of O 3.0 / = 111 of O Q9. Describe the ordered sequence of key steps necessary to calculate the number of s and the mass of a reactant or product when iven the number of s or the mass of another reactant or product. Sample Answer: 1. Balance the equation.. Use the molar mass to convert from rams to s. 3. Use the ratios to find the s of unknown reactants and/or products. 4. Use molar mass to convert from s to rams. TI-Nspire Naviator Opportunities Allow students to volunteer to be the Live Presenter and demonstrate how to use simulation to determine the s and/or mass of products of reaction iven and/or mass of reactants. Use Quick Poll to check for understandin durin the course of the activity. 013 Texas Instruments Incorporated 11 education.ti.com

12 Wrap Up When students are finished with the activity, discuss the four steps used to solve various stoichiometric problems. Assessment Answers to questions are written into the student worksheet. Use Quick Poll to collect answers to questions iven in the student worksheet. 013 Texas Instruments Incorporated 1 education.ti.com