NUPOC SUDY GUIDE ANSWER KEY Navy Recruiting Cmmand
CHEMISRY. ph represents the cncentratin f H ins in a slutin, [H ]. ph is a lg scale base and equal t lg[h ]. A ph f 7 is a neutral slutin. PH < 7 is acidic and ph > 7 is basic.. determine final ph, determine the ttal cncentratin f H ins, and take the lg value liters : liters : ( liters)( ph, ph 5, [ H ] [ H ] 5 mles / liter) ( liters)(. mles ph lg.7 liters M M mles / liter). mles determine the final temperature, assume the heat capacity and density f bth slutins t be similar, then 5 Δh c Δ m h m (c m h p p ) m (c mc p m h m c m c p p ) m (c p ρvc 8 4 66.67! p F ) p ρ V c ρ V c p p V V V. Acid-base chemistry is very imprtant because acids have a big influence n living rganisms. 4. A quantum mdel in which electrns mve arund the nucleus in nly certain allwed circular rbits. hese rbits depend upn the allwable energy levels available t the electrn given by 8 Z E.78 n Jules where n, an integer, is the rbital radius number, and Z is the nuclear charge. he mdel is nt realistic since electrns d nt mve arund the atmic nucleus in prescribed circular rbits. Hwever, the histric imprtance f the mdel is the recgnitin f the quantizatin f energy. 4 n n n n4 E
5. he frmula fr sulfur trixide is SO. Fr each sulfer atm, there are xygen atms, indicating sulfur is in the 6 xidatin state. Assuming all the sulfur reacts t frm sulfur trixide, the number f sulfur atms in 5 g is ml S 6. atms.6 g ml 4 ( 5 g S) 9.9 atms S Fr each sulfur atm, there are xygen atms, thus, 4 (.9 atms S) 748.5 g Oxygen atms O ml atm S 6. 9 6. g atms ml O 6. Cmbining sdium hydrxide (NaOH), a base, with sulfuric acid H SO 4 prduces a salt, sdium sulfate (Na SO 4 ) and water (H O). he balanced equatin can be written as NaOH H SO4 NaSO4 H O 7. he enthalpy change f the previus reactin is given by prducts Frm a standard thermdynamic data table assuming aqueus slutins, f,naoh f,hso4 8. Na, sdium has atmic number. It is a Grup A Alkali metal. he electrn structure is s s p 9. Yes they will react, and the utcme will be a salt (NaCl) and water (H O). he balanced equatin is. he balanced equatin fr the cmbustin f prpane (C H 8 ) in the presence f xygen gas (O ) is hus, by burning mles f prpane, 9 mles f CO will be prduced.. he mathematical expressin fr ph is 94 kj / ml 47 kj / ml 99 kj / ml reac tants 87 86 ( 47 99) 6 s NaOH HCl H O NaCl C H8 5O CO 4H O ph lgh f,naso4 f,ho 87 kj / ml 86 kj / ml ph is n a scale frm (strng acid) t 4 (strng base) with 7 being neutral.
he ph f pure water is 7. If the hydrgen in cncentratin increases the ph will decrease. he disassciatin cnstant f water, K w is defined by H O( l) H O (aq) OH (aq) K w at 5 K w [ HO ][ OH ] [ H ][ OH ]! 7 C [ H ] [ OH ]. (lgh 4 [ H ][ OH ]. Accrding t Le Chatelier s principle, if a change is impsed n a system at equilibrium, the psitin f the equilibrium will shift in a directin that tends t reduce that change. By heating the water, the system will adjust t cnsume energy and the system will shift t the left (think f energy as a reactant) since the prcess is endthermic. hus, if the temperature increases, K w increases. At 6 C, K w. x -.. A rate law fr a reactin invlving a single reactant, A, is an example f a differential equatin aa prducts Δ Rate Δt k n If the reactin is st rder (n) then D A Dt D A k kdt ln kt ln[ A ] kt [ A ] e 7). If a reactin prduces heat and energy flws ut f the system, the prcess is exthermic. If energy is absrbed frm the surrundings, the prcess is endthermic. Physically, the ptential energy in chemical bnds is cnverted int thermal energy and vice-versa. 4. he rate law fr radiactive decay f substances with a half-life, λ is N N e ln k λ N N kt e ln 6 4.54 hus, after 6 years, 5.4% is remaining. 5. Inic bnding ccurs when an atm that lses electrns relatively easily reacts with an atm that has a high affinity fr electrns. ypically inic cmpunds are frmed between metals and nnmetals. he bnding frce develped is very strng due t the electrstatic attractin f the clsely packed ppsitely charged ins.
6. Crrsin is the xidatin f a metal. Crrsin f irn prduces rust 4Fe (aq) O(g) (4 n)h O( l) FeO nho(s) 8H (aq) Cpper frms a layer f greenish cpper carbnate called patina, and silver tarnish is silver sulfide. 7. An acid is a substance that prduces H ins when disslved in water. A buffer slutin is ne that resists a change in ph when either [OH - ] r [H ] ins are added. Bld is a gd example f a buffer slutin as it absrbs acids and bases prduced in bilgical prcesses. 8. A cvalent bnd, prduced by the attractin f the prtn t the electrn hlds the H mlecule tgether. H H 9. he reactin f irn in HCl prduces ferrus chlride and liberates hydrgen gas given by (assuming Fe ges t its st xidatin state) HCl(aq) Fe (s) H (g) FeCl (aq) hus, mles f HCl disslve mle f Fe. he number f grams f Fe disslved by ne liter f a M HCl slutin is mles HCl mle Fe 55.85 g liter mles HCl mle Fe ( liter) 8.8 g Fe