Au Answer Key Mole Ratios How can the coefficients in a chemical equation be interpreted? Why? ‘Abalanced chemical equation can tell us the number of reactant and product particles ions, atoms, molecules or formula units) that are necessary to conserve mass during a chemical reaction. Typically when we balance the chemical equation we think in terms of individual particles. However, in real life the reaction represented by an equation occurs an unimaginable number of times. Short of writing very large numbers (10° ot larger) in front of each chemical in the equation, how can we interpret chemical ‘equations so tha they more realistically represent what is happening in teal life? In this activity you will explore the different ways a chemical reaction can be interpreted. Model 1 - A Chemical Reaction N. G$ 1. Consider the reaction in Model 1. 4. What are the coefficients for cach of the following substances in the reaction? IN, 3H, 2. NH, (@ + 3H,@) > 2NH@ (0 Ho > a | 4, Draw particle models below to illustrate the reaction in Model 1. co Oo ee C = e #4 Do cepctded a dation bei ci ice oe dona te 4, Caleulate the amount of reactants consumed and products made. 4. Record the ratio of N, to H, to NH,. Reduce the ratio to the lowest whole numbers possible. N, H, NH, [Ratio N,HyNH,| Consumed | Consumed Produced (reduced) For a single reaction, how many molecules of each substance would [ 3 L 312 be consumed or produced? Ifthe reation occurred one hun- ded times, how many molecles oo 00 aye ‘would be consumed or produced? \ 8 If the reaction occurred 538 times, how many molecules would be 53 ib 4 Job git consumed or produced? ‘Mole Ratios iL —3, Refer co the data rable in Question 2. 4 How do the reduced ratios in the last column compare to the coefficients in the reaction shown in Model 1? Same 6. Use mathematical concepts to explain how your answer in part a is possible cchlrtenb are a mbe of parbyles | we math bow aie t $4 4 Bven 538 isa small number of molecules to use ina reaction. Typically chemists eeantth gel numbers of molecules. (Recall that one mole is equal co 6.02 x 10” particles.) Consider each situation below as i relates to the reaction in Model 1; N,(g) + 3H,(g) > 2NH,(@). 44. Caleulate che amount of reactants consumed and products made. 4, Record the ratio of N, to H, to NH,, Reduce the ratio to the lowest whole number possible. N, H, NH, Ratio Consumed | Consumed | Produced | _N,:H,:NH, Ifthe reaction occurred 6.02 x 10° times, how many molecules 3 fel Lad niotl 1692 would be consumed or pro- $0040 (.€Ob <( 1.204 xt 3.2 duced? How many moles of each sub- stance would be consumed or produced in the previous situa- | 3 r 34 L: 5, Refer to the data table in Question 4. 4. How do the reduced ratios in che last column compare to the coefficients in the reaction in Model 1? Some 4, Use mathematical concepts to explain how your answer in part a is possible. a mole Ty eae ther wart dasen'by the # of party ke | se the mh A the 2 6. The ratio obta a. What is the mole ratio for the reacti ng. some in Model 12 4, Explain why this ratio is ealled the mole ratio? ratio of moles ied from the coefficients in a balanced chemical equation is called the mole ratio. POGIL™ Activities for High School Chemistry4 8 . Use the mole ratio from the balanced chemical equation in Model 1, N,(g) + 3H,(g) > 2NH,(g), to solve the following problems. Hint: Set up proportions. 4 How many moles of nitrogen would be needed to make 10.0 moles of ammonia? toe mal Myx lel Me 5 1 My Les! WHy 6. How many moles of ammonia could be made by completely reacting 9.00 moles of hydrogen? bnol NH ?ecniel He % SLE 2 (bie salves Bael Mr 6 How many moles of hydrogen would be needed to react completely with 7.41 moles of nikon? Ftp mol Now Zool We 2 oq 23 ml Hy bel a Consider this sicuation as ic relates to the reaction in Model 1, N,(g) + 3H,(g) > 2NH,(g) a, Calculate the amounts of reactants consumed and the amount of product made. 4, Record the mass ratio of N, to H,, to NH,, Reduce the ratio to the lowest whole numbers possible N, H, NH. Mass Ratio Consumed | Consumed | Produced | N:H,NH, How many grams of each Tal BB Pele substance would be consumed 3 ' ee oe produced Inthe davcion in, || PS by Peet Question 42 AL. 9. Refer wo the data table in Question 8. (2 wo, Mole Ratios a, Can the mole ratio from a balanced chemical equation be interpreted as a ratio of masses? No 4 Use mathematical concepts to explain how your answer in part a is possible. AiFhert parbrles hove dttferent masses fo portly i mbes wad mats mbes anct the sane ‘Asa group, develop a plan to solve the following problem. Remember that the mole ratio cannot be used directly in this situation. Note: You do not need to do the actual calculation here. “What mass of nitrogen is needed to produce 30.0 g of ammonia?” (ah — Hts, Jo.og Nay « RNs Leb gee toy Na ® K to em ait [Taste +14 ¥ = 247 g NaModel 2 — Proposed Calculations for Mass of NH, to Mass of ‘Toby's Method xgrams —ImoleN, 300g 2moks NH, “Rachel's Method mole NH, 30.0 gNH, x LMOCNHS © (46 notes NH, 17.0gNH, panel Ns 5 Mele 2 8.860 notes N [EL mole NH, 2 moles NH, — 2 8. 2 olen, x 8°8N: | 24.6 en, 7" TmoleN, | Jerry’s Method 1moleNH, 1 mole N, 30.0 gNH, x — 17.0gNH, 2 moles NH, 1 mole N, 2808N, _ 24% gn 11, Model 2 shows three proposed calculations to solve the problem in Question 10, Complete the calculations in Model 2 by filling in the underlined values. 2 12, Which method does not use the mole ratio in an appropriate manner? Explain, Toby aby of mols aby of mass 77-13. Two of the methods in Model 2 give the same answer. Show that they are mathematically equivalent methods. 24.0 8g. ee: Soe, AE Rede) BOP a wr ° pO gp. A Bg BE 3 Jerry (70 14. Use either Rachel or Jerry’s method from Model 2 to calculate the mass of hydrogen needed to make 30.0 g of ammonia. N,(g) + 3H,(@) > 2NH,(g) 30.0. Ny « Trot Ng (F.0g NH LOL ——> 5.354 A 9-1 U2 2.0090, a reel Ny TH; POGIL™ Activities for High School Chemistry = Ty HyExtension Questions 15. One mole of any gas will occupy 22.4 L of volume at standard temperature and pressure (STP). Consider this situation as it relates to the reaction in Model 1: N,(g) + 3H,(@) > 2NH(g) 14. Calculate the volumes of reactants consumed and the volume of product made. 4, Record the ratio of N, to H, to NH,. Reduce the ratio to the lowest whole numbers possible N, H, NH, | Volume Ratio Consumed | Consumed | Produced | NsH,NH, How many liters of each sub- i le i stance would be consumed 01 2 i y ‘ produced ifthe reaetion occured ae Bile | Ase see 6.02 x 10" times at STP? L1G. Refer to the data table in Question 15. 4. Can the mole ratio from a balanced chemical equation be interpreted as a ratio of volumes for ae Yes B. Use mathematical ned ro explain how your answer in part a is possible. AU pecticle ve Phe fat molar volume 52 volun ad weole cates art the sane 17. Explain why the ratio of volumes is NOT followed in the following reactions. 2Hie) + O09 > 2H(0) NHJg + HCl) > NHC M48L 24L — 0.036L 24L 9 24 0.035 L Malar ‘Velone eu & only ie cannes =a a 18, Which of the following quantities are conserved (total amount in reactants products) in a chemical reaction? Find an example or counter example from this activity to sup- port your answer for each. a, Molecules ps 4 Moles No e Mass Yes 4. Volume No € Atoms ofan element pg Mole Ratios 5