A.P. CHEMISTRY. SOLUTIONS AND ACID BASE CHEMISTRY. p 1

Transcription

1 A.P. CHEMISTRY. SOLUTIONS AND ACID BASE CHEMISTRY. p 1 (Nte: questins 1 t 14 are meant t be dne WITHOUT calculatrs!) 1.Which f the fllwing is prbably true fr a slid slute with a highly endthermic heat f slutin when disslved in water? 1) The slid has a lw lattice energy 2) As the slid disslves, the temperature f the slutin increases ) The resulting slutin is ideal. 4) The slid is mre sluble at higher temperatures 5) The slid has a high energy f hydratin 2. Tw pure substances, A and B, each melt at 9.4 C. An unknwn pure substance Q als melts at 9.4 C. Melting pints are btained n mixtures f Q + A, Q + B, and A + B, and in each case the melting pint is belw 9.4 C. Which f the fllwing cnclusins d these data supprt? 1) Q, A, and B are all different 2) Q,A, and B are all the same ) Q is the same as A but different frm B 4) Q is the same as B but different frm A 5) A is the same as B but different frm Q. The freezing pint f p-dichlrbenzene is 5.1 C; its mlal freezing pint cnstant is 7.10 /m. A slutin cntaining 66.7 grams f slute per kilgram f p-dichlrbenzene freezes at 50.2 C. What is the apprximate mlecular weight f the slute? 1) 70 2) 160 ) 62 4) 28 5) An aqueus slutin is 50. % by weight methanl, CH OH. (MM f methanl is 2, that f water is 18) What is the mle fractin f the methanl? 1) ) 0.6 ) ) ) Equal vlumes f a 0.10M Ca(NO ) slutin and 0.20M NaNO slutin are mixed. The mlarity f the cmbined nitrate in after mixing is 1) 0.05 M 2) 0.10 M ) 0.15 M 4) 0.20 M 5) 0.0 M 6. At 20 C.,the vapr pressure f tluene is 22 trr and that f benzene is 75 trr. An ideal slutin, equimlar in tluene and benzene is prepared. At 20 what is the mle fractin f benzene in the vapr in equilibrium with this slutin? 1) 0.2) 0.29 ) ) ) 0.8

2 A.P. CHEMISTRY. SOLUTIONS AND ACID BASE CHEMISTRY. p 2 7. A student wishes t prepare 2.00 liters f mlar KIO.( mlecular weight = 214) The prper prcedure is t weigh ut 1) 42.8 grams f KIO and add 2.00 kg f H O 2) 42.8 g. f KIO and add H O until the final hmgeneus slutin has a vlume f 2.00 liters )21.4 g. f KIO and add H O until the final hmgeneus slutin has a vlume f 2.00 liters. 4) 42.8 grams f KIO and add 2.00 liters f H O 5) 21.4 grams f KIO and add 2.00 liters f H O 8. Which f the fllwing aqueus slutins has the highest biling pint? 1) 0.10 M ptassium sulfate, K SO 2 4 2) 0.10 M hydrchlric acid, HCl ) 0.10 M ammnium nitrate, NH NO. 4 4 ) 0.10 M magnesium sulfate, MgSO 5) 0.20 M sucrse, C H O Hw much water must be added t 100. ml. f.0 M NaOH t prduce a 0.50 M slutin? 1) 500 ml 2) 600 ml. ) 00 ml. 4) 6.0 liter 5) 5.0 liter 10. When the temperature is increased, the slubility f 1) mst slids and mst gases increases 2) mst slids and mst gases decreases ) mst slids increases, and mst gases decreases 4) mst slids decreases, and mst gases increases 5) all substances whse disslving prcess is exthermic increases. 11. Sme slutins, such as an alchl-water mixture, deviate frm Rault's Law in that the vapr pressure f the slutin may attain a value which is higher than the vapr pressure f either pure cmpnent. This culd be caused by 1) a decrease in the vlume f the slutin 2) evapratin f the slvent being impeded by the presence f slute particles n its surface, and vice versa ) The intermlecular attractins between the alchl mlecules being lwered by the presence f the water mlecules, and vice versa 4) the intermlecular attractins between alchl mlecules being raised by the presence f the water mlecules, and vice versa 5) the attractins between water and alchl mlecules far exceeding the attractins between the like mlecules.

3 A.P. CHEMISTRY. SOLUTIONS AND ACID BASE CHEMISTRY. p 12.Henry's Law wuld best predict the change f slubility in water with changing temperature fr the gas 1) SO 2) HCl ) NH 4) N O 5) O Liquids A and B frm an ideal mixture. At 20 the vapr pressure f pure A is 100 mm.; that f pure B is 50 mm. A slutin cntains 2.0 mles f A and 8.0 mles f B. 1. What is the partial pressure f vapr A in equilibrium with this slutin? 1) 20 mm 2) 25 mm ) 10 mm 4) 40 mm 5) 60 mm 14. What is the mle fractin f A in the vapr abve the slutin? 1)0.20 2) 0.25 ) 0. 4) ) 0.80 Remaining questins were meant t be dne WITH calculatrs where needed. 15. Which f the fllwing slutins shuld have the highest biling pint? (tricky) 1) 5.8 g f NaCl in 100 g f water (mw f NaCl 58 ) 2) 92 g f C H OH in 100 g f water (mw f alchl is 46) 2 5 ) 6.1 g f KClO in 100 g f water. (mw f KClO is 122) 4) 18.0 g f C H O in 100 g f water. (mw f glucse is 180) ).0 g f NaOH in 100 g f water. ( mw f NaOH is 40 ) If 25.0 ml. f M BrO is mixed with 0.0 ml. f M Br slutin that + cntains a large excess f H, the amunt f Br frmed accrding t the equatin 2 abve is ) 5.00 X 10 mle 2) 8.10 X 10 mle ) 1.5 X 10 mle 4) mle 5) mle Fe + MnO + 8 H 5 Fe + Mn + 4 H O 4 2

4 A.P. CHEMISTRY. SOLUTIONS AND ACID BASE CHEMISTRY. p In a titratin experiment based n the equatin abve, 25.0 milliliters f an acidified Fe -- slutin requires 14.0 milliliters f standard mlar MnO 4 slutin t reach the 2+ equivalence pint. The cncentratin f Fe in the riginal slutin is 1) M 2) M ) M 4) M 5) 0.14 M 18. Hw many grams f silver nitrate,(m.w.=170) are required t prepare 25 ml. f a 0.15 M slutin? 1) 6.4 g 2) 0.64g ) 1.02 g 4) 10.2 g 5) 2.2 g 19. The vapr pressure f water at 50 is 92.5 mm f Hg. What is the vapr pressure f a slutin cntaining g f glucse, (mw=180) disslved in 180 g f water? 1) 84.1 mm 2) 8.2 mm ) 46.2 mm 4) 10 mm 5) 9.25 mm 20. Assuming that the slutin is ideal, what is the biling pint f an aqueus NaCl slutin which freezes at C? (The freezing pint cnstant is 1.86 ; the biling pint cnstant is 0.52 ) 1) ) ) ) ) Part II. Answer questin I, and any three f the thers. Extra credit if yu d all f them. Nte that questin I is wrth 0 pints, while the ther essays are 12 each. Yur ttal scre will then be multiplied by 1.6 t btain an essay grade. I. A cmparisn f the theries f Arrhenius, Brönsted, and Lewis shws a prgressive generalizatin f the acid base cncept. A. Outline the essential ideas f each thery. (9 pints) B. Belw are five chemical reactins. They are all acid base reactins accrding t at least ne f the theries described in part A. Fr each reactin indicate which theries apply, and which d nt. Briefly explain each answer. (15 pts.) 1. HCl + NaOH NaCl + H2O

5 A.P. CHEMISTRY. SOLUTIONS AND ACID BASE CHEMISTRY. p 5 2. SO + CaO CaSO 4. BCl + NH BClNH 4. NH + HNO NH4NO 5. CHNH 2 + H2O CHNH + + OH C. Fr the reactin Cu + 4 H O Cu(H O), identify the Lewis acid and the Lewis base, and explain yur selectins. ( 6 pts. ) Remaining essays are 12 pints each. II. In each f the fllwing cases, a slight excess f dilute base is added t 0.05 M slutin f the acid. The resulting heats f neutralizatin per mle f acid reacting are indicated fr each acid base reactin. Heat f neutralizatin a) HCl + NaOH 1.7 kcal. b) HNO + KOH 1.7 kcal. c) HCl + NH 12.6 kcal. d) CHCOOH + KOH 1.4 kcal. e) HClO 4 + KOH 1.7 kcal. A. Accunt fr the fact that the heats are the same in a, b and e B. Accunt fr the fact that they are different in c and d. III. A 100 ml. slutin f 0.40 M NaOH is mixed with 50.0 ml f 0.20 M H SO. Calculate the mlarity f Na +, SO 2-, and OH - in the resulting slutin IV. A slutin cntaining 12.0 g f slute disslved in 800 g f water freezes at C. What is the mlecular weight f the slute? The slutin bils at a temperature f 90. What cnclusin can yu draw abut the nature f the slute? V. Cncentrated slutins f NH in water are 28 % NH by weight, and have a density f 0.90 g/ ml. Find a) The mlarity f NH in the slutin b) the mlality f NH in the slutin c) the mle fractin f WATER in the slutin. d) the freezing pint f the slutin, if the inizatin f the NH is negligible.