Chemistry 1252 S17

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Chemistry 1252 S17 Final Exam Review 1 If 140 g of CO2 gas has a volume of 23104 mL at 28 C what is its pressure in atm 2 150 atm of wet ammonia gas is dried then decreased from 780 mL to 400 mL at constant temperature What is the final pressure of dry ammonia in mm Hg if PH2O = 283 mm Hg when the gas was collected 3 A scuba tank gas mixture contains 30 grams of oxygen to every 970 grams of helium What is the partial pressure of oxygen when this mixture is delivered at a total pressure of 87 atm

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4 A 6100 g sample of an ideal gas in a 200 L container is held at a constant pressure of 0900 atm and a constant temperature of 2900 K Calculate the molar mass of the gas 5 (a)Draw accurate 3‐D structures for PCl3 and PCl5 including all lone pairs Draw a crossed arrow to show the molecular dipole for the polar compound PCl3 PCl5 (b)Which compound would boil at the higher temperature Justify your answer using intermolecular forces to explain the differences 6 Identify the primary intermolecular force experienced by pure samples of (a) through (d) (a) H2S (b) CH3OH (c) H3C-CH2-CH3 (d) He (e) Rank these in order of increasing vapor pressure (at the same temperature) 7 Which of the following molecules can form hydrogen bonds with other molecules of the same kind Circle your answer(s) CH3F CH3NH2 H2O HI CH3-O-CH3 CHCl3 HCOOH

lt lt lt

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8 Ethylene glycol C2H6O2 is a component of automobile antifreeze If a 350 mass solution of ethylene glycol in water is prepared at 20 C and the density of the solution is 1154 gmL what is the molarity of the solution 9 The density of a 05000 M solution of glucose (Mglucose = 1802 gmol) in water is 2026 gmL

(a) Calculate the boiling point of this solution in degC

(b) Calculate the vapor pressure of this solution at 25 degC in mm Hg if the vapor pressure of H2O

at 25 degC is 238 mm Hg 11 Strontium-90 is a radioactive isotope that is a product of an atomic bomb explosion It has a half-life of 281 years How long will it take for a 500 g sample of Sr-90 to decay to 500 g

What will the mass of the sample be after 281 years g

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12 The initial rates listed were measured in methanol solution for the reaction C2H4Br2 + 3 I C2H4 + 2 Br + I3

Experiment Initial [C2H4Br2] Initial [I] Initial Rate of I3

Made (Ms)

1 0127 M 0102 M 645105

2 0343 M 0102 M 174104

3 0203 M 0125 M 126104 (a) Which experiments must be compared first in order to find the order with respect to one of the reactants (b) What is the overall order of the reaction (c) Calculate the rate constant k with units 13 A decomposition reaction at 25 degC has a frequency factor of 10 x 10-3 s-1 and activation energy of 500 kJmol What is the rate constant of the reaction 14 Write the equilibrium expression Kc for the reaction

CH3COOH (aq) + H2O (l) CH3COO- (aq) + H3O+ (aq) What type of K value does this represent more specifically (Circle one)

Kc =

Kf Ka Kb Kw Kp Ksp

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15 At 298 K there is typically much more molecular oxygen than ozone in the air Oxygen and

ozone convert according to the reaction 3 O2(g) 2 O3(g) (a) If 00520 M O3 and no oxygen is loaded into a container and the equilibrium concentration of O3 is 9281032M O3 create an ICE table to find numerically the equilibrium concentration of O2 (b) Calculate Kc at this temperature (c)Explain why the value of Kc supports the amount of oxygen and ozone found in the air

16 Consider the reaction 2 SO2 (g) + O2 (g) 2 SO3 (g) at a certain temperature

(a) If the initial pressures of SO2 O2 and SO3 are 0400 atm 0750 atm and 0132 atm respectively calculate Qp for this reaction

(b) If the equilibrium partial pressure of O2 is 0600 atm calculate the equilibrium pressures of SO2 and SO3

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(c) Calculate Kp at this temperature Does your value of K make sense (K vs Q) 17 Which will have the higher pH You do not need to show your work (a) 0200 M KOH or 0200 M Ba(OH)2 (b) 00500 M HClO4 or 00500 M HF (c) 100 M IO3

(Ka of HIO3 is 17101) or 100 M C3H5O3 (Ka of HC3H5O3 is 1410-4)

Hint Still donrsquot need work 18 Circle the correct equilibrium position shift and effect on the value of K for the reaction

(CH3)2CHOH (g) (CH3)2CO (g) + H2 (g) for which H = +573 kJ

STRESS EQUILIBRIUM POSITION SHIFT

NUMERICAL VALUE OF K

(a) temperature is increased

Left No Shift Right Lower No Change Higher

(b) volume is increased Left No Shift Right Lower No Change Higher

(c) H2 is added Left No Shift Right Lower No Change Higher

(d) a catalyst is added Left No Shift Right Lower No Change Higher

19 Below are mechanisms for a catalyzed and an uncatalyzed reaction Write the overall rate law for each circle any catalysts and put a box around any intermediates

0100 M KOH 0100 M Ba(OH)2

(circle one) 00500 M HClO4 00500 M HF

(circle one)

100 M IO3 100 M C3H5O3

(circle one)

k1

Step 1 O3 (g) O2 (g) + O (g) (fast) k-1

k2

Step 2 O3 (g) + O (g) 2 O2(g) (slow)

k1

Step 1 O3 (g) + NO(g) NO2(g) + O2(g) (slow) k2

Step 2 O3(g) O2(g) +O(g) (fast) k3

Step 3 NO2(g) + O(g) NO(g) +O2(g) (fast)

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20 (a) Trifluoroacetic acid CF3COOH is one of the strongest weak acids Calculate the Ka of CF3COOH if a 0150 M sample has a pH of 1020 (b) Calculate the percent ionization of this sample 21 Decide whether each compound will form acidic basic or neutral solutions (a) calcium carbonate (b) KCl (c) ammonium nitrate (d) NH4CN given Kb(NH3) = 18105 and Ka(HCN) = 491010

acidic neutral basic

acidic neutral basic

acidic neutral basic

acidic neutral basic

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22 Consider a buffer made from HNO2(aq) and NaOH(aq) Ka(HNO2) = 45104 Suppose 100 g of solid NaOH were added into 200 L of 100 M HNO2 Calculate the pH of the buffer 23 A 500 mL sample of 0100 M sodium hypochlorite is titrated with 0200 M HCl (Ka (HClO) =29 x 10-8) Calculate the pH after the addition of each of the following volumes of acid (a) 125 mL (b) 25 mL

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24 Calculate the value of the thermodynamic equilibrium constant K for the following reaction C(graphite) + O2(g) CO2(g)

Standard Free Energies of Formation (at 25 degC)

Formula ΔGfdeg (kJmol)

CO2 -3944 25 For the reaction

CH3OH(l) + 3

2 O2(g) 2H20(l) + CO2(g)

the value of ΔGdeg is -7026 kJ at 25 degC Other data are as follows

ΔHfdeg (kJmol) at 25 degC Sdeg (JmolK) 25 degC CH3OH(l) -2386 127 H20(l) -2858 70 CO2 -3935 214

Calculate the absolute entropy Sdeg per mole of O2(g)

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26 (a) Calculate the standard free energy change ΔG for the following at 25 C MgO(s) + C(graphite) Mg(s) + CO(g) ΔH = 49118 kJ ΔS = 19767 JK (b) Is this reaction spontaneous at 25 C If not at what temperature can we make this reaction spontaneous