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Final exam Practice Answers                       Chem 1A                                  Name___________________

2.205 lb.= 1.000 kg        °F =°C180/100 + 32           K = °C + 273.15

5280 ft = 1 mile         d_lead=11.6 d=m/v         Show your work for credit.

2.54 cm = 1 inch        d_gold=19.3 v=4/3_r³       Remember your significant figures.

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Cs, Rb, K, Ba,Sr, Ca, Na, Mg, Al ,Mn ,Zn ,Cr, Fe, Co, Sn, Pb, H, Cu, Ag, Hg, Au

Most active                                         F₂, Cl₂, Br₂, I₂                        Least Active

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PV=nRT             R = .08206 literxatm/(Kxmole)                R = 62.37 literxtorr/(Kxmole)

KE = 3RT/(2N)          KE = 1/2 mv² rate₂/rate₁ = (m₁/m₂)^1/2         (P + an²/V²)(V - nb) =nRT

KE = 1/2 mu² = 3RT/(2N)       where R is 8.314 J/(Kxmole) and N is Avogadro’s number

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w = F x d          KE = ¹/₂mv²          PE = mgh         g=9.80 m/s²          1 calorie = 4.184 joules.

DE = q + w = q -PDV          DE = E_final - E_initial       DH = H_products - H_reactants

DH°_(rxn)= SDH°_f(products) - SDH°_f(reactants)

C = q/DT Heat Capacity               q = CDT For objects such as calorimeters.

c = q/(m x DT) Specific Heat        q = smDT For substances.

Properties for water---> c_ice=.48 cal/g°C,  c_water= 1.00 cal/g°C,     DH_f= 80 cal/g,     DH_v= 540 cal/g

H_2(g) + 1/2O_2(g) -> H₂O_(l)                 DH°_f = -285.5 kJ/mol

C_(s) + O_2(g) ---> CO₂                        DH°_f = -393.5 kJ/mol.

2C_(s) + 3H₂ + 1/2O₂ ---> C₂H₅OH_(l) DH°_f = - 277.6 kJ/mol.

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DE = hn          E_k = hn - E_b                  l = h/mv        c = ln          c =3.00x10⁸m/s

E_n = - R_H(1/n²)                    DE = R_H(1/n_i² - 1/n_f²)          R_H = 2.18x10^-18J

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DH_rxn = SDH_{(bond breakage)} - SDH_{(bond formation)}

Bond dissociation energies in kcal/mole

C=O is 127.0,    O=O is 59.6,    H-O is 102.4,     H-C is 80.9,    C-C is 88.0

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1   Make the following conversions. Give answers to proper number of sig. figs.

a)   25.0 miles/hour to centimeters/millisecond.

1.11centimeters/millisecond

b)   454 in³ to cm³.

7440 cm³

c)   125 mg to kg.

.000125 kg

d)   Convert 265 K to °F.

[(265 - 273)°C]x180°F/100°C +32 = 17.6°F

e)   What is the density of lead in kg/liter?

         11.6kg/liter

2    How much heat is required to raise the temperature of 10.0 g of ice from -10.0°C to 50.0°C?

1348 calories total

3    Name the following compounds or ions.

a. Cu₂SO₃ __copper(I) sulfate_____      b.    Al(HCO₃)₃ __Aluminum hydrogencarbonate_____

c.  Cr₃(PO₄)₂ _Chromium(II) phosphate  d.     HClO ___Hypochlorous acid_

e. P₂O₅ ___diphosphorous pentoxide___

4    Give the formulas for the following compounds.

a) Zinc phosphate __Zn₃(PO₄)₂___      b) Calcium chlorite __Ca(ClO₂)₂__

c) Cobalt (IV) chlorate __Co(ClO₃)₄__  d) Magnesium hypochlorite __Mg(ClO)₂__

e) Sodium perchlorate __NaClO₄__

5    Balance the following equations. If no reaction occurs write N.R.

a) 2C₃H_10(g) + 11O_2(g) à 6CO₂ + 10H₂O

b) Cu_(s) + MgCl_2(aq) à NR

c) 2H₃PO_4(aq) + 3Ba(OH)_2(aq) à Ba₃(PO₄)₂ + 6H₂O

d) 2HC₂H₃O_2(aq) + Ba(HCO₃)_2(aq) à Ba(C₂H₃O₂)₂ +2CO₂ + 2H₂O

e) Hg₂(NO₃)_2(aq) + NaCl_(aq) à   Hg₂Cl_2(s) + 2NaNO₃ 

6    6.00 g of CH₄ is reacted with 5.00 g of Oxygen. How many grams of water are formed?

      2.81 grams of water, not 13.5 grams.

7     3.00g of aluminum are reacted with H₂SO₄. What volume of hydrogen gas is collected at STP?

      3.74 liters

8     What is the wavelength in nm of light emitted when an electron drops from the n=6 to n=2 energy levels in hydrogen?

 E_photon= DE_atom hc/l=R_h(1/n_f² -1/n_i²)     l=hc/[R_h(1/n_f² -1/n_i²)]

l=(6.626x10^-34 Jsx3.00x10⁸ m/s)/[2.18x10^-18J(1/2² -1/6²)]=410 nm ??

9    Put the following atoms, Na, K, S, Cl, and Mg, in order of

a) increasing size. _____<_____<_____<_____<_____

b) increasing ionization energy _____<_____<_____<_____<_____

c) increasing electron affinity _____<_____<_____<_____<_____

10    Write the complete and shorthand electron configuration for Cu,, Fe³⁺ and Br^-.

                    Complete                                        Shorthand

Cu   1s²,2s², 2p⁶, 3s², 3p⁶, 4s¹,3d¹⁰              [Ar]4s¹, 3d¹⁰ Robin hood 

Fe³⁺ 1s²,2s², 2p⁶, 3s², 3p⁶, 4s⁰,3d⁵               [Ar]4s⁰, 3d⁵  Remove two electrons from outer shell first, 4s, then one from the 3d. Remember remove from outer shell first.

Br ^- 1s²,2s², 2p⁶, 3s², 3p⁶, 4s²,3d¹⁰,4p⁶          [Ar]4s²,3d¹⁰,4p⁶  Add an electron for the charge

11    How much heat is given off when 100 g of ethanol (C₂H₅OH) is burned completely? Hint: Find DH first.

14     The molecular shape of the CCl₃^- ion is

a. square pyramidal. b. tetrahedral.

c. trigonal planar. d. pyramidal.

e. square planar.

15     Of the following molecules, the only one with no permanent dipole moment is

a. water, H₂O. b. acetone, CH₃COCH₃.

c. carbon dioxide, CO₂. d. sulfur dioxide, SO₂.

e. 1,2-dichlorobenzene, C₆H₄Cl₂.

16     In which of the following species is resonance most likely to take place? More than one is possible.

a.                             b.  

c.                           d.

e.    

17     The tetrahedral bond angle is approximately

a. 90º. b. 180º. c. 109.5º. d. 120º. e. 72º.

18     Each of the following species contains at least two p bonds except

a. N₂⁺ b. HCCH.

c. CO₂ d. CN^-.

e. H₂CCCH₂

19     The vapor pressure of a liquid increases with an increase in temperature. Which of the following statements best explains this increase?

a. The average kinetic energy of molecules is greater; thus more molecules can enter the gaseous state.

b. The number of gaseous molecules above the liquid remains constant, but these molecules have greater average kinetic energy.

c. The faster-moving molecules in the liquid exert a greater pressure.

d. All the molecules have greater kinetic energies.

e. The intermolecular forces between the molecules decrease at higher temperatures.

20     Which of the following compounds is expected to have the highest boiling point?

a. CH₃CH₂CH₃ b. CH₃CH₂CH₂CH₃

c. CH₂CH₂OH       d. CH₃OCH₃

e. CH₃CH₂F

21     The forces of attraction between molecules of H₂ are

a. hydrogen bonds. b. dipole-dipole attractions.

c. covalent bonds. d. London forces.

e. dipole-induced dipole attractions.

22     Which of the following compounds shows an abnormal boiling point because of hydrogen bonding?

a. CH₃Cl                     b. CH₃OCH₃

c. CH₃SH                    d. CH₃NH₂

e. HCl

23     Which of the following phase changes is or are endothermic?

a. vaporization only          b. sublimation only

c. condensation only         d. both a and b

e. both b and c

24     Which of the following compounds would be expected to have the highest crystal lattice energy?

a. LiF           b. LiI

c. CsI           d. CsF

e. NaCl

25     Which compound below would be expected to be the least soluble in water?

a. CH₃CH₂COOH         b. CH₃CH₂CH₂NH₃

c. CH₃CH₂OHCH₃          d. CH₃CH₂CH₂F

e. CH₃CH₂NHCH₃

26     Determine the freezing point of a 0.050 m solution of glucose in water. (K_f =1.86ºC/m.)

27     Which of the following solutes dissolved in 1.0 kg of water would be expected to cause the water to freeze at the lowest temperature?

a. 0.0015 moles of glucose, C₆H₁₂O₆ b. 0.0015 moles of HF

c. 0.0020 moles of methanol, CH₃OH d. 0.0015 moles of H₂SO₃

e. 0.0015 moles of HNO₃

28     In the following oxidation-reduction reaction,

8H⁺_(aq) + 6Cl^-_(aq) + Sn(s) + 4NO₃^-_(aq) à SnCl₆^2-(aq) + 4NO_2(g) + 4H₂O

the oxidizing agent is

a. H⁺                   b. Cl^-

c. Sn                  d. NO₃^-

e. SnCl₆^2-

Extra credit: Balance the following equations in the form in which they appear. (5 Points Each)

6Cl^- +  Cr₂O₇^2- +   6 I^- +  14  H⁺ à     2CrCl₃ +    3 I₂ +  7H₂O

 

 

4  H⁺  + C₂H₅OH +    MnO₄^-2 à   Mn⁺² +  HC₂H₃O₂  +  3 H₂O         acidic