1. 2010-2011 Chemistry SOL Blitz

2. Question #1 Which of the following atoms contains 30 protons, 40 neutrons and 28 electrons? A: 70 Zn +2 B: 70 Zn -2 C: 40 Zn +2 D: 30 Zr -2

3. Answer to Q#1 Letter A: 70 Zn +2 is the answer. Why? The format for chemical symbols is A X charge z Remember, A = mass, which equals protons + neutrons Z = atomic number = protons Charge = protons – electrons

4. Question #2 The element boron has only two stable isotopes. One stable isotope has a mass number of 10 and the other has a mass number of 11. Which of the following could be the atomic weight of the element? A: 9.5 B: 10.8 C: 11.7 D: 12.4

5. Answer to Q#2 Letter B: 10.8 is the answer Why? The mass of an element on the periodic table is the weighted average of all the isotopes of that element

6. Question #3 An atom of Argon—40 contains— A: 18 protons and 18 neutrons B: 18 protons and 22 neutrons C: 18 protons and 40 neutrons D: 20 protons and 20 neutrons

7. Answer to Q#3 Letter B: 18 protons and 22 neutrons Why? The 40 in Argon-40 is the mass of the isotope Remember mass = protons + neutrons (electrons have no mass) Argon has an atomic number of 18, so there 18 protons

8. Isotope/ Ion Quick Review Isotopes of an element have the same atomic number (protons) but different masses (hence different neutrons) Both protons and neutrons have a mass of 1 Electron’s mass is not taken into account in the mass of an atom Ions are anything with an electrical charge Positively charged ions have lost electrons Negatively charged ions have gained electrons

9. Question #4 A scientist comparing K and Ca would find that K has a— A: lower electronegativity and a smaller atomic radius B: higher electronegativity and a smaller atomic radius C: lower electronegativity and a larger radius D: higher electronegativity and a larger atomic radius

10. Answer to Q#4 Letter C: lower electronegativity and a larger atomic radius Why? Electronegativity gets higher as you go across a period and atomic radius gets smaller as you go across a period K is farther left so it must have a lower electronegativity and larger atomic radius

11. Question #5 Which of the following elements is the most reactive? A: Cs B: Sr C: Mg D: Rb

12. Answer to Q#5 Letter A: Cs Why? All these elements are metals—the most reactive metals are the largest Atomic radius gets larger as you go down a group Cs is farthest down so it is the largest and most reactive

13. Trends Quick Review Trends as you go down a group: larger atomic radius, lower electronegativity, lower and ionization energy (easier to lose an electron) Trends as you go across a period: smaller atomic radius, higher electronegativity, and higher ionization energy (harder to lose an electron) Remember IE is the energy it takes to lose an electron Electronegativity is the ability to gain an electron

14. Quick Review Continued Metal reactivity: Largest metals = most reactive metals. Remember metals like to lose electrons Non-metal reactivity: smallest non- metals = most reactive non-metals. Remember non-metals like gain electrons Noble gases are non-reactive—they have a full valence shell

15. Question #6 A bond between an element of group 2 and an element of group 17 will be: A: ionic B: Nonpolar covalent C: Polar covalent D: Metallic

16. Answer to Q#6 Letter A: Ionic Why? Group 2 elements are metals (also known as alkaline earth metals) and group 17 (or 7) elements are non- metals (also known as halogens) Metals + non-metals = ionic bonding

17. Bonding Quick Review Covalent bonding = sharing of electrons between non-metals Ionic bonding = transferring of electrons between metal + non-metal Nonpolar covalent bond = equal sharing of electrons between non- metals Polar covalent bond = unequal sharing of electrons between non-metals

18. Question #7 What is the name for Cu 2 S? A: Copper sulfide B: Copper (I) sulfide C: Dicopper sulfide D: Dicopper monosulfide

19. Answer to Q#7 Letter B: Copper (I) sulfide Why? Copper is a transition (d block) metal, so you must use roman numerals to indicate its charge Look behind S for the charge of Cu. Charge is +1 so copper (I) sulfide

20. Question #8 Which of the following is the formula for carbonic acid? A: HC B: HCO C: HO D: H 2 CO 3

21. Answer to Q#8 Letter D: H 2 CO 3 Why? It’s an acid so H must come first. Carbonic = carbonate = CO 3 -2 H +1 + CO 3 -2 = H 2 CO 3

22. Question #9 What is the molecular formula of tetraphosphorus decoxide? A: PO B: P 4 O C: P 4 O 10 D: PO 10

23. Answer to Q#9 Letter C: P 4 O 10 Why? Tetra = 4 and deca = 10 So P 4 O 10 Remember, when using prefixes don’t switch—simply write what’s given

24. Naming Quick Review Must use roman numerals to indicate charge of a transition metal Only use prefixes when the compound is all non-metals If an acid has hydro prefix then it’s H+element If no hydro prefix for an acid then it’s H+polyatomic

25. Question #10 ___C 3 H 4 + ___O 2  ___CO 2 + ___H 2 O When the equation above is balanced, what is the sum of the coefficients? A: 4 B: 5 C: 8 D: 10

26. Answer to Q10 Letter D: 10 Why? C 3 H 4 + 4O 2  3CO 2 + 2H 2 O; so 1+4+3+2 = 10 Don’t forget the law of conservation of mass says the reactants side = products side

27. Question #11 Which of the following is an example of a decomposition reaction? A: 2AgCl  2Ag + Cl 2 B: CuO + H 2 O  Cu(OH) 2 C: AgCl + Mg  MgCl 2 + Ag D: HCl + Na(OH)  H 2 O + NaCl

28. Answer to Q #11 Letter A: 2AgCl  2Ag + Cl 2 Why? Decomposition is when you start with one reactant and break into 2 products Letter B = synthesis; letter C = single replacement and letter D = neutralization reaction

29. Question #12 12 x 403 = What is the answer to the above problem expressed with proper sig figs? A: 5,000 B: 4800 C: 4830 D: 4836

30. Answer to Q#12 Letter B: 4800 Why? When multiplying or dividing, you use lowest # of sig figs for your answer 12 only has two sig figs, so your answer can only have two

31. Question #13 How many atoms of Na are in 0.300 moles of Na? A: 0.0131 atoms B: 7.86x10 21 atoms C: 1.81x10 23 atoms D: 6.02x10 23 atoms

32. Answer to Q#13 Letter C: 1.81x10 23 atoms Why? 0.300 moles Na x 6.02x10 23 atom 1 mole = 1.81x10 23 atoms

33. Question #14 How many moles are in a 342grams of CaO? A: 6.10 moles B: 56.1 moles C: 1.92x10 4 moles D: 3.67x10 24 moles

34. Answer to Q#14 Letter A: 6.10 grams Why? 342g x 1mole CaO = 6.10 moles 56.08 grams 56.08 grams is the molar mass of CaO from the Periodic Table

35. Moles Quick Review When multiplying/dividing use lowest # of sig figs for answer When adding/ subtracting use lowest # of decimal places for answer Mass  Moles use mass of Periodic Table = 1 mole Moles  Particles use 1 mole = 6.02x10 23 particles Moles  Liters at STP use 1 mole = 22.4 L

36. Question #15 Be + 2HCl  BeCl 2 + H 2 Using the above reaction, what mass of beryllium was consumed in the reaction if 4.0 moles of HCl were used? A: 2.0grams B: 9.0 grams C: 18.0 grams D: 36.0 grams

37. Answer to Q#15 Letter C: 18.0 grams Why? 4.0molsHCl x 1mols Be x 9.01gBe 2 mols HCl 1 mole Be = 18.0 grams Be

38. Letter #16 2C 2 H 6 + 7O 2  4CO 2 + 6H 2 O In an experiment, 0.500 mols of C 2 H 6 were reacted with 1.50 moles of oxygen gas. Which of the following is the limiting reactant in this experiment? A: C 2 H 6 B: O 2 C: CO 2 D: H 2 O

39. Answer to Q #16 Letter B: O 2 Why? 0.500molsC 2 H 6 x 4mols CO 2 2 mols C 2 H 6 = 1.00 mols CO 2 1.50molsO 2 x4mols CO 2 = 0.857molsCO 2 7 mols O 2 Since O 2 produces less CO 2, it must be the limiting reactant C and D shouldn’t even be choices b/c they are products!

40. Stoich Quick Review Mass A  Mols A  Mols B  Mass B Go from mols A  mols B using mol to mol ratio from coefficients of balanced equation Limiting reactant is the one used up first. It also produces the smaller amount of product % yield = (actual/theoretical) x100 Can also use stoich to go from mass/mols of A to liters of B; use 22.4 L = 1mol at STP

41. Question #17 Which of the following is NOT a part of the kinetic molecular theory? A: Gases move in a straight, continual motion B: Gases have no volume themselves C: Gases participate in inelastic collisions D: Kinetic energy is directly related to temperature E: Gases feel no attractive forces

42. Answer to Q#17 Letter C: Gases participate in inelastic collisions Why? Gases actually participate in elastic collisions. The other 4 parts are all TRUE

43. Gas Laws Quiz Review Boyle’s Law  P 1 V 1 = P 2 V 2, where P and V are inversely related. Charles’ Law  V 1 /T 1 = V 2 /T 2 Gay-Lusac  P 1 /T 1 = P 2 /T 2 Combined Gas Law  (P 1 V 1 )/T 1 = (P 2 V 2 )/T 2 Ideal Gas Law  PV = nRT, where R = 0.0821 (L*atm)/(mol*K)

44. More Gas Laws Review Must always convert temperature from celsius to KELVIN! Absolute zero is -273C or 0K! Absolute zero is the point where all motion slows down and stops Dalton’s Law  P 1 +P 2 +P 3 … = P total

45. Question #18 Which of the following phase changes occurs at the arrow? A: Sublimation B: Melting C: Evaporation D: Condensation

46. Answer to Q#18 Letter B: melting Why? Graph always goes S, L, G—look at pic on right The arrow points to line b/w solid and liquid Only phase changes there are melting (S  L) or freezing (L  S)

47. Phases Quick Review 6 phases changes –Melting (S  L)--Freezing (L  S) –Evaporation (L  G) --Condensation (G  L) –Sublimation (S  G) --Deposition (G  S) Molar heat of fusion = amount of energy needed to melt 1 mole of a substance Molar heat of vaporization = amount of energy needed to evaporate 1 mole of a substance Specific heat capacity = amount of energy needed to raise the temperature of 1 gram of a substance by 1˚C  use q = mxC p xΔT

48. IMF Quick Review Four different intermolecular forces –London dispersion (weakest) = nonpolar covalent molecules –Dipole-dipole = polar molecules –Hydrogen bonding = H connected to N, O or F bonding to another O, N or F –Ionic (strongest) = metal + non-metal Don’t forget to do the arrow test to determine polarity of a molecule

49. Question #19 How many moles of MgCl 2 are present in 3.00 liters of a 0.150M MgCl 2 solution? A: 0.0500 moles B: 0.450 moles C: 1.35 moles D: 20.0 moles

50. Answer to Q#19 Letter B: 0.450 moles Why? Molarity (M) = mols/liters So 0.150 M = x/3.00 L (0.150M)(3.00L) = x X = 0.450 moles

51. Solutions Quick Review Molarity(M)=mols of solute/L of solution Molality(m)=mols of solute/kg of solvent Freezing point depression: ΔT f =(-K f ) (m)(n) Boiling point elevation ΔT B =(K b )(m)(n) Remember if the solute is covalent, n = 1

52. Equilibrium Quick Review Write K expressions as products over reactants. Remember the coefficients in the balanced equation are used as exponents in the K expressions Solids and liquids are not included! Catalysts lower the activation energy of a reaction Enthalpy (ΔH) and entropy (ΔS) determine the spontaneity of a reaction - ΔH (exothermic) and +ΔS (more disorder) means a spontaneous reaction

53. Question #20 PCl 5(g) + heat  PCl 3(g) + Cl 2(g) Which of the following will cause an increase in the equilibrium concentration of Cl 2 gas? A: The addition of PCl 3 gas B: The removal of PCl 5 gas C: A decrease in temperature D: An increase in temperature

54. Answer to Q#20 Letter D: An increase in temperature Why? Heat is a reactant, so increase reactant side, equilibrium shifts to product side Letter A causes shift to L; letter B causes shift to L; and letter C causes shift to L

55. Acid/Base Quick Review pH = -log[H + ] pOH = -log [OH - ] pH + pOH = 14 [H + ][OH - ] = 1x10 -14 [H + ] = 10^(-pH) [OH - ] = 10^(- pOH) pH < 7 = acid pH > 7 = base