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Chemistry Review Class - June 16 and June 17, 2007 #2

This review class covers various topics in chemistry including atomic structure, bonding, compounds, reactions, and more.

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Chemistry Review Class - June 16 and June 17, 2007 #2

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  1. REVIEW CLASS, JUNE 16 AND JUNE 17 2007 #2) Aluminum is therefore Z = 13 and A = 27. ANS-2)The number of protons is the nuclear charge (+13) and the number of electrons (neutral atom only). 27 Al There is no charge written, it is neutral. 13 Electrons = Protons in a neutral atom. #4) ANS-2: Both the proton and neutron have a mass of 1 AMU (1/12 the mass of C-12) #5) Potassium (K) is in the same GROUP and therefore has the same valence shell electron configuration. #7) Li has the highest melting point (table “s”).

  2. #6) % Composition = part/molar mass x 100 % composition of Al= 2 Al/ Al2(SO4)3 = 2(26.98)/342 x 100 = 15.8% #8) Mg, Ca and Ba are in the same group, ANS=2 #9) Fe(II)S iron sulfide (TABLE “F” S2- IS SULFIDE). NOTE THET THE NEGATIVE ION OF A NON-METAL ENDS IN “IDE”, SULFER (S) IS sulfiIDE. THE ROMAN NUMERAL IS THE POSITIVE CHARGE OF THE METAL Fe. Fe2+ S2- Fe2S2 FeS, ans choice 1) #11) Covalent bonds are in molecular substances only.ANS-1 #12) NaCl(aq) is a homogenous mixture because the solution of salt in water is one phase, (aq).

  3. #13) A DOUBLE BOND IS 4 ELECTRONS. #14) CH4 IS TETRAHEDRAL (4-BONDS), SYMETRICAL AND NOT POLAR. NOTE THE BONDS ARE POLAR, BUT THE MOLECULE IS SYMETRICAL. ANS-3 #15) As you remove electrons, the e- cloud gets smaller and a proton is unpaired. The atom gets smaller and positive – ANS-2. #16) Heat always flows from more (hotter) to less (colder). The 50o choice is cooler then the 60o sample and heat flows into it, ANS-1. Also the cooler object has the least average kinetic energy. #17) Real gasses are most ideal at high temp (break attractions and causes more random motion and collisions) and low P (spreads the particles). ANS 3– 750K and 20kPa – highest T and lowest P. #18) At similar T, P equal volumes of any gasses are equimolar, ANS-3 #19) 4L of CO2

  4. #20) ETHYNE IS AN ALKYNE AND HAS A TRIPLE BOND, SIX SHARED ELECTRONS. #21)ANS-4 Both have the molecular formula C2H6O. #22)ANS-4 2-pentene has a double bond (CnH2n) #23)ANS-1 Oxidation causes the oxidation number to INCREASE from reactant to product. –1 to +2 is an increase of 3 (3 mol of e- are lost). #24) The rate of a reaction increases with concentration (molarity for solutions) and temperature (T). ANS – 4 has the highest molarity and Temperature. #25) Conductors are soluble (aq) salts from table “F”, acids or bases. KOH is a base (table “L”, Or a group one or two hydroxide) , the higher molarity gives the most ions upon dissociation KOH  K+ + OH-. ANS-4, highest molarity base. NOTE CH3OH is an alcohol which is NOT an electrolyte (even though it looks like a base, it is not a base).

  5. #26) A H+ ion may also be written as a) H2O2 b)H2O c) OH- d) H3O+ , ANS-d), by definition H3O+ is equivalent to H+ #27) One acid base theory states that an acid is: a) an e- donor b) a neutron donor c) ANS- an H+ donor d) an OH- donor #28)Which Isotope will decay spontaneously and emit a particle with a charge of +2? A) Fe-53 b) Cs-137 c) Au-198 d) Fr-220 Radiation of +2 charge is an alpha particle, and table “N” lists natural decay. Find the alpha emitter on table n from the choices. The answer is Fr-220 d), the only alpha emitter – Cs-137, Fe-53 and Au-198 are beta #29) Co-60 undergoes beta decay, this type of radiation is a) natural transmutation b) artificial transmutation c) fusion d) fission The decay of Co-60 is on table “n”, it is natural transmutation. #30)Given the reaction, compared to the total charge of the reactants the charge of the total products is; 2Al + 3Cu2+ 2 Al3+ + 3 Cu 2(0) + 3(2+) = 2(3+) + 3(0) 6+ = 6+ the same

  6. #31) % Composition = part/molar mass x 100 FIND %Br in AlBr3 % composition of Br = 3 Br/ AlBr3 = 3(79.9)/256.7 x 100 = 93% ANS-4 #32) Al+3 has lost 3 electrons (each + charge represents a lost electron). The neutral atom has 13 protons, thus there are 13 electrons in the neutral atom. If three e- were lost 10, are remaining. ANS-4 #33 The excited state must have the same # of electrons as the neutral atom, however one or more must be at a higher energy level (outermost shell) that the ground state of the periodic table ( for Al it is 2-8-3), 13 electrons.The ans is 1) 2-7-4 (13 e-), one electron promoted from shell 2 to shell 3. #34) non-metals are brittle non conductors. This cannot be METALLIC as metals are soft, and metallic solids conduct. Look for an element on the non-metal side of the table, it is S, 16 protons. #35)X in XBr3 can best be solved by oxidation number rules. The sum of the oxidation numbers = 0 for this neutral substance. XBr (remember, halogens are usually 1- in binary compounds) X + 3(-1) = 0, X=3+, group 13: ANS-3

  7. #36) a sample contains 65.4 g of Zn, 12 g of C, and 48.0 g of Owhat is the mole ratio? Ans-3 1:1:3 YOU DID NOT NEED TO DIVIDE BY THE SMALLEST OR REDUCE IN THIS PROBLEM, THE RAW RATIO WAS THE MOST REDUCED WHOLE NUMBERS ALREADY. #37) Which process would best separation two liquids with different molecular polarities? 1) filtration 2)fermentation 3) distillation 4)conductivity Distillation separates based on boiling point, which differs with polarity (more polar boils at higher temp).

  8. #38) For the balanced equation AgNO3(aq) + NaCl(aq)  NaNO3(aq) + AgCl(S) AB + CD  CB + AD A double replacement - must form a solid . #39) At 40oC about 63 g of KNO3 Will dissolve in 100g of water. If you already have 35g, you can dissolve About 28g more. Closest ANS-1(29) (40oC,63g)

  9. #40) Bottle 1 shows particles spread out (as opposed to clustered) FILLING the container VOLUME AND ASSUMING THE SHAPE, must be a gas. #41)How many moles of NaCl are needed to make 3.0L of 2.0M NaCl solution. M = mol/L 2.0M = mol/3.0 L; 6 mol ANS-3 #42) Lewis valence dot for sulfide is: 2- [ [ RED ELECTRONS WERE GAINED S #43 ANS-4 Add enough water to make the SOLUTION 1L total, including the solvent which displaces a small amount of water.

  10. #44) there is NO change of T in a phase change, in this problem: q = mass x heat of fusion, q = 5.00 x 334J/g = 1670 J released OR –1670 J because freezing is exothermic. #45) Choice 1,2,3 do not change the formula – all are physical – 1) is evaporation- a phase change, 2) is melting, 3) is simple crushing. ANS-4 because it reacted. #46) the Gas phase always has the highest entropy, followed by liquid and the solid has least. Entropy also increases with Temp. Ans-4, a gas. #47) Addition does not produce a mineral acid (HCl), addition can add 2 Cl atoms and substitution cannot. This reaction is addition, With addition you need a double bond, choose the alkene or alkyne. ANS-2 – is unsaturated – can undergo addition (CnH2n-2).

  11. #48) In the reaction 4 Fe + 3 O2  2 X, There must be 4 Fe on the right, the answer must be Fe2O3. (Ans-2) #49)FACT 1- Both are acids (table K) FACT 2- Acids turn blue litmus to red. ANS 1). #50) From U-238 to U-234 is alpha ( mass # decreased by 4, atomic # by 2 indicates alpha.) From Th-234 to Pa-234 the atomic number increased by 1 indicating beta decay. Pa-234 to U-234 is also beta for the same reason. ANS -4

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