Chapter 11 Structure of Matter 133 Answers to the Conceptual Questions

Transcription

1 hapter 11 Structure of Matter 1 Answers to the onceptual Questons 1. These models gave detaled explanatons for events that had already occurred but lacked any predctve power.. Many examples apply.. Although cruel, one mght magne sealng off the machne and thus takng away essentals such as food and water for a perod of tme. 4. If the Sun s movng, we must be usng the geocentrc model.. Addtonal examples n whch expermental results agree wth a model strengthen our belef n t. However, a model can never be proven true. The next brown can he tres mght snk. 6. The new model mght be that only det drnks float. The data s consstent wth ths new model but the model remans tentatve untl all possble cans are tested. 7. The atomstc nature of matter s not mportant for most day-to-day actvtes n whch macroscopc propertes are all that are mportant. 8. The alchemsts contrbuted to a new world vew n whch external appearances were not the essence of matter. In addton, they developed a wde varety of technques for manpulatng materals.. Water, salt and grante are not elements as they can be separated nto ther consttuent parts. 10. arbon monoxde s a compound as t can be separated nto ts consttuent parts, carbon and oxygen. 11. The powder s a compound, because the mercury combnes wth somethng n the ar. 1. Many examples apply. The most common response from students s combnng hydrogen and oxygen to form water. 1. ompounds are new substances wth ther own propertes resultng from substances combnng accordng to the law of defnte proportons, whereas mxtures retan the propertes of the orgnal consttuent parts. 14. Water and salt form a mxture that retans the propertes of the orgnal consttuent parts amu 16 amu 6 amu 16. The atomc mass of the two ron atoms s 160 amu (16 amu) 11 amu. The atomc mass of one ron atom must be half ths, whch s 6 amu. 17. An atom of slver s 108 tmes as heavy as an atom of hydrogen. It would therefore take 108 tmes fewer slver atoms to make a gram than t would hydrogen atoms. 18. A mole always contans an Avogadro s number of partcles. 1. They have the same number of molecules. 0. Both contaners hold the same number of molecules. arbon doxde molecules comprse atoms each whereas oxygen molecules comprse only atoms each. Therefore the carbon doxde contaner wll contan 0% more atoms. 1. An atomc mass number of grams of any substance contans an Avogadro's number of unts. Therefore, you would need grams of sulfur.. An atomc mass number of grams of any substance contans an Avogadro's number of unts. The atomc mass of water s 18 amu. Therefore, you would need 18 grams of water.. The deal gas model cannot be used wth lquds as the dstances between the partcles are no longer large enough to neglect nter-partcle nteractons. However, t does tell us that the partcles are much closer together. 4. As the pressure ncreases, the average dstance between partcles decreases. Ths ncreases the lkelhood of non-contact nteractons, whch volates the prmary assumpton of the deal gas law.. The ball exerts the larger pressure because t has a smaller surface area touchng the floor.

2 14 hapter 11 Structure of Matter 6. When you push on a thumbtack you dstrbute the force over a relatvely large area, whch results n a low pressure. Applyng the same force to the much smaller head of a needle produces a huge pressure, whch causes the skn to puncture. 7. The surroundng ar pressure ncreases as you descend nto the valley. Because the walls are flexble, the pressure of the gas also ncreases and ts volume must decrease. 8. The tre must support the same weght. Wth half the pressure t must have double the contact area, whch s 400 square centmeters.. The ncrease n the number of molecules means that more molecules wll be httng the walls per unt tme. 0. As they heat up, the ar molecules gan knetc energy. Therefore, they move faster and strke the walls more frequently wth more momentum. 1. The perfume molecules travel very crooked paths.. The added energy causes the average speed to ncrease.. The large volume of alcohol causes a larger change n the heght of the column, thereby amplfyng the effect due to a gven change n temperature. 4. hanges n the atmospherc pressure wll also affect the heght of the alcohol column.. ondtons such as atmospherc pressure and the purty of the water must be mantaned to guarantee a repeatable, fxed temperature. 6. Body temperature vares among people and wth tme for a gven person. 7. Although both students have temperatures of degrees, the student wth the o temperature has the hgher fever because the elsus degree s larger than the ahrenhet degree. 8. Reference to g shows that 0 o s the hotter of the two temperatures.. Reference to g shows that the temperature s o. 40. Reference to g shows that the correspondng temperature s o. 41. The freezng pont of water s 0 o + 7 K 7 K. 4. Lqud ntrogen bols at 77 K 7 K 16 o. 4. The average knetc energy of the molecules doubles. 44. The absolute temperature would have to quadruple, because knetc energy depends on the square of the speed. 4. They would have the same average knetc energes as they have the same temperature. 46. Both gases have the same average knetc energes, so the helum atoms would have the greater average speed. 47. The partcles have more knetc energy. Therefore, they are movng faster and strke the walls more frequently wth more momentum. 48. The pressure drops to one-half ts orgnal value. 4. The volume doubles. 0. As the temperature of the gas decreases, ts volume decreases. We assume that the pressure stays the same because the walls are flexble. 1. The temperature drops to one-half on the Kelvn scale.. The flexng of the sdewalls causes the tre to heat up. Therefore the pressure rses (assumng that the volume stays fxed).. The partcles strke the walls more frequently producng a larger average mpulse wth the walls of the contaner. 4. The volume drops to one-thrd of ts orgnal value.. The more energetc molecules leave va evaporaton lowerng the average knetc energy and, therefore, the temperature of the remanng water. 6. The more energetc alcohol molecules leave va evaporaton lowerng the average knetc energy of the

3 hapter 11 Structure of Matter 1 remanng alcohol. Ths causes a flow of energy from your body to the remanng alcohol. 7. rom the coolng of ther bodes due to the evaporaton of the water on them. 8. Bolng removes the hgher knetc energy molecules. As more heat s added, the rate of the molecules leavng the surface ncreases, leavng the average knetc energy of the remanng molecules (and thus the temperature of the water) fxed. Answers to the Exercses 1. Mh m h 1g Mo 4 g m o 8g g m n 14 g. Mn Mh 18 g 84 g m h g. Oxygen s the lmtng amount. Therefore, 16 g + (1 g) 18 g. 4. Oxygen s the lmtng amount. Therefore, 48 g + (1 g) 84 g.. Bread s the lmtng amount g bread s 0 g bread 0 sandwches sandwch m 60 g 100 g s s m 000 g 0 10 g 800 g of ham h 6. Oxygen s the lmtng amount 1000 g oxygen water 16 g oxygen 6. moles of water mole of water m 18 g 11 g of water water water m m m 000 g 11 g 87 g of hydrogen h tot water 1g 1amu # amu g 1g 1amu # amu g 1kg 1amu 18 amu kg 10 atoms 10 atoms #. 10 molecules g 1 amu 10. # molecules 4 amu g 11. The number of lters tells us how many molecules of the orgnal combne to form ths number of molecules of the product. Usng these numbers as multplers n a chemcal equaton gves us 1 + H 1x H y Makng sure that we have the same number of atoms of each knd on each sde, we get x 1 and y. 1. See the soluton to Exercse 11 for the procedure. 1O + 1H 1HO

4 16 hapter 11 Structure of Matter cm 10 m # 10 A atom 10 ( 10 m) 0.01 m m 0 P atm A π 0.00 m m 16 ( 0.)( 1600 kg)( 10 m s ) A m P. 10 Pa P P 1 f L P f P f Tf T T T 7 K + 7 K 600 K 18. P 100 atm 1. f L 160L 160balloons P f 1. atm Tf 1 K 0. Pf P ( ps + 14 ps) 4.1 ps T K Therefore, the gauge pressure s.1 ps. Tf 10 cm 1 K 1. Pf P 1atm 1.6 atm f T 100 cm K f Pf 1000 cm 1 atm. Tf T 7 K 4 K 4 P 00 cm atm Answers to the Problems n Problem Solvng 1. Because 1 L of ntrogen produces L of ammona, 40 L of ntrogen wll produce 80 L of ammona.. Because L of carbon monoxde produce L of carbon doxde, 0 L of carbon monoxde wll produce 0 L of carbon doxde.. Because 1 molecule of methane produces molecules of hydrogen, 100 L of methane wll produce 00 L of hydrogen. 4. Because molecules of acetylene combne wth molecules of oxygen, t wll requre. tanks of oxygen to burn each tank of acetylene cm 1 m t A 10 m 100 cm 10 cm 0 L 1000 cm 1 m t A 400 m 1 L 100 cm cm

5 hapter 11 Structure of Matter cm 7 1 m 4 A 10 cm 1000 m ; less than one-half t 10 cm 100 cm 4 8. At L 00m 10 m 0L 10 m A 0 cm atoms 8 A atom 10 cm M 0.01 kg m. 10 atoms 1 ( mv ) Pa.7 10 kg/atom ( 8 amu) ( 40 m s ) cm kg P 10 cm 1m 1amu 1 1. P ( mv ) ( 44 amu) kg 100 cm 400 m s 400cm 1amu 1m Pa ( m ) 7 ( kg)( 8 10 m ) P v 44 m s m Average velocty only depends on the temperature of the gas. Assumng that the gas on the nsde of the tre s at the same temperature as the gas outsde, they wll have the same average velocty. P m 1000cm 1m cm kg 1600 m s 10 mv T ( T ) ( 0 ) 17.8 T ( T ) ( 68 ) 0 T T T Tc T T c T ( T )

6 18 hapter 11 Structure of Matter T Tc T Tc TX T Xf 0 T Tf + Tb Tf TXb T Xf TX T Xf 0 T Tf + ( Tb Tf ) + ( 180 ) 140 TXb T Xf 0 T T 7 + 0X + 0X 17X Tcb T cf 100 c cf 0. TX TXf ( TXb TXf ) T T f TR TRf + ( TRb TRf ) 4 R + ( 180 R) Tb T f 180. The Rankne degree s the same sze as the ahrenhet degree. You would stll be "runnng a three degree fever.". T T 7 K 0 K 7 K 7 K T TK 7 K 10 K 7 K 7 4. T T 7 K 17 K 7 K T v n K T mo 1 vo 11 m s 4 m s m 0.88 vh mc v m c h n Tf 7 K f L.L T K P P f P f P f Tf T K 86 K 1 Pf P atm 8 atm 1 f 4 The rms speed of the gas molecules stays the same. It depends only on the temperature of the gas. f Pf 100 cm atm Tf T 400K 00K 7 P 400 cm 1 atm

7 hapter 11 Structure of Matter Tf 00 cm K Pf P atm 1.4atm f T 800 cm K P 80 atm f 4L 1L P f 1.1 atm Because there wll be 4 L left n the tank, we can only blow up 87 balloons at 1 L each. P 100 atm f 0.6 m 48 m P f 1. atm Because there wll be 0.6 m left n the tank, we only have 47.4 m to blow up the balloons. f 47.4 m 100 cm balloon 000 cm 1 m 480