i Mienna Avery Relative Mass and the Mole Hw can atoms be counted using a balance? Why? cae the following equation fora chemical reaction: 2H, + O, > 2H,0 can be interpreted as cwo molecules of and one molecule of oxygen combining ro form owt malar Bros Scheele eazns an oreo mae Una tee eon is done with an unimaginable number of molecules. How then ‘do chemists know they have on ra The molecules need to be quickly counted! How do we count molecules? The answer it ral ed the mole, This acivgy will tart by considering wo egg fumes (a chicken farmer and a dhl farmer). They produce such lage numbers of eggs that they cat count them all individually, so ‘cy Count in dozens of ‘eggs in some cases, while in other cases they use mass. ‘Weighing is often easier than counting! Model 1 — Eggs x Chicken Quail Ratio of masses nee te Maso tee Nabe of ete zea 1 37445 1 2346 ee 10 FA ag 10 BAQ Io] 8 (ib, F199 438 1,0759, let Tdoren | UY5Q | _reowen | 28,009 al Tmalion [% [HA0,000g) _tmiion [2,249 000g] Iu: | 1. Consider the data in Model 1 ‘a. What is the mass of standard chicken egg? 31.44q +6, What is the mass ofa standard quail egg? THA Show te how the 16:1 ‘ratio of masses was calculated in the last column of Model 1. ae yell 2. Usea calculator to Zomplete the table in Model 1, Divide the work among group members. Reduce al ratios to the lowest whole numbers possible Relative Mass and the Mole\ 3. Imagine you have wo bskew--one filled with qual eg and one led wich the same number of chicken eggs 4 Which basket would be heavier? , Chicken €qgs ni h. How many times heavice would that basket be? wy i") Tne basket: ¢ id be lex hea eGR Aptian 4. A farmer weighs out SF ehicken oes. , «Wma gael hc les ee =x Ob Be ee © iby 72049 4. Ifthe farmer had weighed out 32.0 pounds of chicken eggs (rather chan kilograms), what ‘mass of quail eggs would be need co weigh out to have the samme number of eggs in both _ e head 1.0 tbs 5. A farmer makes up a new counting unit called a “cluckster.” “a. Lf the farmer had 3 clucksters of chicken eggs and 3 clucksters of quail eggs, what could you usa aie eee me SF omicher? CGgS Whi) be Ib Himes heaner sa I SEE TA ‘ Lt doerit mater Now Many C993 are 11 a "Clock ster: @ ie lel voto will aloalys be 410e aS long as +e ead Taig MUNDY OF CG9S 1S Hhe Jane Tees take what we learned in the egg model and apply it to atoms. Like eggs, atoms of the same clement may have slightly diferent masses (remember isotopes). The periodic table lists an average atomic mass for the atoms ina sarmple of each element. These masses are recorded in “atomic mass units” where 1 amu is approximately equal to the mass of a proton (or neutron). 2 POGIL™ Activities for High School Chemistryo 4 Model 2 ~ Atoms Numberof fo Salfar Ratio of Rati of atomsin the | Mas ofthe | Numberef | nas ofthe | sumbersof | mits” | TStpen® | same | simcnsie | pl atoms u 16.00 amu 1 32.00amu_| | { | _10 [fet Don a ! | | [—téeren_ | 07m | tdomen | >t OMY] | I Lnillion | : ; a illion [{k,000,000mp] 1 million PQ oyp,subsamol |. 1 NZ Imole [| 1600grams | _1mole | 32.00gams | 1° | ore ‘Note:The masses shown fr oxygen and sulfur have been rounded to make the arithmetic ait esis 6. What is the ratio of the mass of an oxygen atom to the mass of a sulfur atom? N2 7. fide the work Fill in the table in Model 2 in a similar fashion to the eggs table in Model 1. Divi evenly among group members. Reduce all ratios to the lowest whole numbers possible. Circle the phrase below that completes the sentence. ‘When two samples contain the same number of atoms —___________—— the masses of the “he rato ofthe sample the masses are unrelated. samples will be equal ‘masses wll beequl tothe ato ofthe atoms mases eis why it is not necessary to know how many atoms are in “1 mole” to finish the last row of 1¢ table in Model 2. The mass Hoty cael riot lepend an +e ee Ki Cems not imple, a long as the number J the Jt oh BR. able the number of oxygen atoms in a 16.00 Ibs sample compare to the number of sulfur atoms in a 32.00 Ibs sample? C We vaio of Maes oy a molt 6 0 enane amolt of es IRR ot ey er er ae 27 bs | mole of sulfue. Estimate how many atoms are in the bottle. Your group must reach consensus. | ator 1 Read This! ‘long time ago chemist discovered what you have just discovered: The relative masce of the elements can be wied to “count” atoms, If you measure out a sample equal to an atoms atomic mass in grams, you always tend up with the same number of atoms. Chemists call that quantity the mole—a quantity of any sample whose mass is equal to its atomic mass in grams. Relative Mass and the Mole 3Model 3 ~ Molar Mass ass of One Mole of Particles Average Mass ofa Single Particle re lar Mas) 1 atom of hydrogen (H) 1.01 amu 1 mole of hydrogen atoms (H) 101g 1 atom of copper (Cu) 63.55 ama Tmole ofcopper atoms (Cu) _| 63.558 1 molecule of oxygen (O,) 32.01 amu mole of oxygen molecules (©,) | 32.018 |_1 molecule of water (HO) 18.02 amu mole of water molecules (H,O) | 18.02g 1 formula uni of sodium 58.44amu| | 1 mole of sodium chloride 5844 g chloride (NaC) formula units (NaC) oe uae at a periodic table. What number in each element box. wuld chemist use to find the es in the “ fas of a Single Particle” column in Model 3? * ‘We Og iid se tues yanioh Ove GIVEN with amu ! 13, How is the mass ofa single particle changed to get the mass of one mole of particles? same. runic Bena tne pera dade, Dt WM QraUn Is fix 14. Which sample contains more atoms, 18,016 amu of water or 18.016 g of water? Explain. Rgiara iy av rnvdh lauger une Vit) he cetomi¢ ra ss UNF, So Ae IB. Ob saMp!e Nd rma ators © Ifthe formula mass of iton(ID) sulfare (FeSO,) is 151.9 amu, what is the molar mass of iron(ID) sulfate? 151g 16. Usea periodic table to calculate the molar mass of ammonia (NH) 110g How would the number of atoms in a 1.01 g sample of hydrogen compare to che number of “sme number Of ceo! in each Samp!e Would be Hae : Joumne Read This! ‘So how many “things” are in & mole? By estimating the sizeof atoms and taking volume measurements oF 11 mole samples scientists can estimate that 1 mole = 6.022 > 10% particles or 602 200 000 000 000 000 000 000 particles (More than you could count in a lifetime!) ‘This number is called Avogadro's number, named after Amedeo Avogadro. 4 POGIL™ Activites for High School Chemistry