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UP Chemical Society in partnership with UP 49ers brings you

Chemistry Review SeriesChem 17 2 ND Long Exam

I. Modified True or False. Write TRUE if the statementis correct. Otherwise, write FALSE then change theunderlined word(s) to make the statement true.

1. (LAB) The presence of common ion in a solutiondecreases the Ksp of the compound.2. Ions having a noble-gas electron configuration or anouter shell of 18 electrons are colorless in solution.3. Upon increasing the temperature, an exothermic reaction

will be displaced, favoring the product formation4. (LAB) Ag + can be used to separate Cl - from SO 42- byprecipitation.5. Based from the Le Chatelier’s Principle and the equation4HCl(g) + O 2(g) ⇌ 2 H2O(g) + 2Cl 2(g) at temperature753K. The ∆H°=-144 kJ. If the volume V is reduced by a

factor of 15, the equation(n H O ) (n Cl )

(n HCl )4

(n O ) must be increased

by a factor of 15.6. (LAB) An endothermic reaction will have decreasedsolubility.7. Strong field ligands such as CN- usually produce high spincomplexes and small crystal field splittings.8. PbI2(s) is less soluble in KNO 3 solution than in wateralone.9. When the number of moles of gas does not change inupon attaining equilibrium, Kp = (Kc) 0 = 1. 10. (LAB) Addition of 3.0 M CH3COOH to the whiteprecipitate yielded from the addition of 0.1 M BaCl 2 to thetest sample indicates the presence of NO 3- witheffervescence.

II. Cause and Effect. Identify the effect of the conditionon the indicated parameter. Write increase, decrease, no effect, orindeterminate.

Condition Parameter

1. No autozero done Absorbance

2. 0.2 M FeCl3 and 0.2 M

KSCN was used instead of0.002

Experimental

molarabsorptivity

3. Cuvette held on clear sides Absorbance

4. The test samples duringanion separation were diluted

Accuracy ofanionidentification

5. Using 0.2 M CaCl2 insteadof 0.1 M in the determinationof the solubility of Ca(OH) 2

Solubility ofCa(OH)2

6. 0.02 M NH3 was used inNH 3-NH 4+ buffer systeminstead of 0.2 M

Buffer capacity

III. Multiple Choice. Write the letter of your answer. 1. Consider the complex ion [Mn(OH 2 )6 ]2+ with 5

unpaired electrons. Which response includes all thefollowing statements that are true ?

I. It is diamagnetic.II. It is a low spin complex.III. The metal ion is a d 5 ion.IV. The ligands are weak field ligands.

V. It is octahedral.

a) I, II

b) III, IV, Vc) I, IVd) II, V

2. Given only the following indicators, with their pKs, in thelaboratory, which would you use to monitor theneutralization of a substance occurring at pH 5.35?

Indicator pK2,4-Dinitrophenol 3.96Bromophenol blue 4.10

p-Nitrophenol 7.15Phenolphthalein 9.50

a) 2,4-Dinitrophenolb) Bromophenol bluec) p-Nitrophenold) Phenolphthalein

3. For the reaction O 2(g) ⇌ 2O(g), what condition favorsthe production of oxygen atoms?

a) Low temperature and low pressureb) High temperature and high pressurec) Low temperature and high pressured) High temperature and low pressure

4. Which of the following will be the hydrolysis reactionstate of NH 4NO 3?

a) acidic since NH4+ hydrolyzes.b) basic since NH 4NO 3 is a basec) pH neutral since NH 4+ and NO 3- hydrolyzes

forming acid and base, which neutralizes eachother.

5. Consider the violet-colored compound,[Cr(OH 2 )6 ]Cl3 and the yellow compound, [Cr(NH 3 )6 ]Cl3

Which of the following statements is false?

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a) Both chromium metal ions are paramagnetic

with 3 unpaired electrons.b) Δoct for [Cr(NH 3 )6 ]3+ is calculated directly

from the energy of yellow light.c) Δoct for [Cr(OH 2 )6 ]3+ is less than Δoct for

[Cr(NH3 )6 ]3+ .d) The two complexes absorb their

complementary colors.

6. Arrange the following in increasing order of solubility inammonia: CH2CH2Cl, CH2OH, H 2O.

a) CH2CH2Cl < CH 2OH < H 2Ob) CH2OH < CH 2CH2Cl < H 2O

c) H2O < CH 2CH2Cl < CH 2OHd) CH2CH2Cl < H 2O < CH 2OH

7. Given a chemical equilibrium, which will favor the reversereaction?

a) A + 2B ⇌ AB2 ; ↑ [A]b) 3T + 2U ⇌ T3U2 ; ↓ [T3U2]c) 28CI⇌ 7C4 + 14I 2 ; ↑ [C4]d) None of these.

8. Calculate the [S2-] in a 0.1 M H2S solution that is also 0.1M in HCl. Use the overall acid dissociation constant K 12 =

1.1 x 10-21

= K 1K 2 for H 2Sa) 1.1x10-10 b) 2.2x10-10 c) 1.1x10-20d) 1.1x10-21

9. Magnetic measurements indicate that [Co(OH 2 )6 ]2+ has3 unpaired electrons. Therefore, the hybridization of themetal's orbitals in [Co(OH 2 )6 ]2+ is:

a) sp3 b) sp2dc) dsp2 d) sp3d2

10. Calculate the pH of the resulting solution when 0.040moles HNO 3 was added to 0.500 L 0.380 M each ofHC3H5O2 and NaC 3H5O 2. K a of HC 3H5O 2 = 1.30 x 10-5.

a) 4.700b) 4.886c) 5.700d) 5.886

IV. Problem Solving. 1. Five standard solutions of FeSCN2+ were prepared

and their absorbance were determined at its λmax=465nm (b= 1 cm). The data for calibration is shownbelow:

Sol’n Abs [Fe(SCN)2+ ]1 0.063 2x10-5 2 0.134 5x10-53 0.286 1x10-4

4 0.576 2x10-4

5 1.183 4x10-4 a. Determine the equation of the calibration curve and

the molar absorptivity of Fe(SCN) 2+ .b. Shown below are the components of the unknown

solutions with absorbance determined using a differentblank solution but with the same wavelength.

0.002 MFeCl3, mL

0.002 MKSCN, mL

0.1 MHCl, mL Abs

Blank 0 5 5 0Unk 1 2.5 5 2.5 0.343Unk 2 3.75 5 1.25 0.459

Unk3 5 5 0 0.593i. Determine the initial concentration of Fe3+ and

SCN- of each unknown solution.ii. Determine the equilibrium concentration of Fe3+

and SCN- of each unknown solution.2. A 0.10 mol sample of AgNO 3 (s) is dissolved in1.00 L of 1.00 M NH 3. How many grams of KI can bedissolved in this solution without a precipitate of AgI (s) forming?3. A fresh 10 mL 0.02 M acetate buffer with pH =4.30 is to be prepared for the experiment. The onlysolutions available in the laboratory are 0.05 M acetic acid

0.05 M NaOH and 0.05 M HCl. pK a of HOAc = 4.76.a) Which two solutions will you use to prepare theacetate buffer? Determine the amounts of each.

b) What will be the resulting pH when 0.05 mL ofHCl was accidentally dropped to the 10 mL preparedbuffer?4. Molde and Dorog, both inorganic chemists, study thereactions of phosphorus halides where they mixed 0.1000mol of PCl5 with 0.0900 mol of Cl2 and 0.0900 mol of PClin a 0.0500 L flask at 250°C (Kc = 4.2 x 10-2).

a. Write the balanced chemical equation.b. In which direction will the reaction proceed?

c. If [PCl5 ] = 0.2050 M at equilibrium, what are theequilibrium concentrations of the other components?5. What will be the mass of Phosphoric acid that you willuse to make a 500 mL solution having a phosphateconcentration of 4.24x10 -24? pH of solution is 2.2pKa1=2.16. pKa 2=7.21. pKa 3=12.32. MW of phosphoricacid is 97.995 g/mol

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