# review hw need in a few hours

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Henrys law  Sgas=kH Pgas

large kh values produce large solubility values

which of the following solutes should have largest henrys law constant in water

1.  Ar

2.  Xe

3.  CO

4.  CH3CH3

5.  CO2

My guess CO

=============================

If a reaction is known to be first order in reatactant A and third order in reactant B

By what factor will the rate change if the concentration of a is triples and concentration of b is doubled

1.  4xfaster

2.  6x faster

3.  7x faster

4.  24x faster

5.  48xfaster

My work

K[A]1[B]3

K  3[A]1  2[B]3

3^1(2^3)k[A]1[B]­­3

24x faster

===========================

Which of the following molecules would be the least soluble in water

1.  Ch3ch2ch2ch2ch2ch2oh

2.  Ch3ch2ch2ch2ch2oh

3.  Ch3ch2ch2ch2oh

4.  Ch3ch2ch2oh

5.  Ch3ch2coh

The longer the carbon chain, the more greasy the molecule, the less water soluble. Ch3ch2ch2ch2ch2ch2oh

======================================

Choose the situation below would result in an endothermic h solution

1.  When |ΔHlattice| > |ΔHhydration|s

2.  When |ΔHlattice| = |ΔHhydration|s

3.  When |ΔHlattice| < |ΔHhydration|s

4.  When |ΔHsolvent| >> |ΔHsolute|s

·  I chose #2

===========================

Reaction rate constant for a particular second order reaction is .55M-1s-1

if the initial concentration of reactant is .6 M how many seconds will it take for the concentration to decrease to .1M

1.  2.5s

2.  15.2s

3.  32s

4.  1.75s

5.  11.8s

my work

k=.55Ms

[a]0=.6

[a]t=.1

(1/.1)-(1/.6)=.55t

T=15.15

15.2

[1/(A)] - [1/(Ao)] = kt

==============================================

What is Mass % solute of a 1.74 molal h2so4 solution in water

1.  1.1%

2.  10.2%

3.  16.4%

4.  14.6%

5.  19.6%

My guesswork

moles H2SO4 = 1.74
mass H2SO4 = 2.00 mol x 98.078 g/mol=170.69 g
mass water = 1 Kg = 1000 g

1000+170
mass solution = 1170.7 g
% = 170.7 x 100/ 1170.7=14.58

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Which of the following ions should have the least exothermic delta h hydration

1.  Na+

2.  Mg2+

3.  Al3+

4.  Ca2+

5.  Sr2+

Ion with largest charge should have the most exothermic enthalpy of hydration

Least Na

=====================================

Pu-239 radioactively decays via a first order process of 24200 years

If you started with a 5kg sample, how long would it take for 4.688kg to decay

1.  24200 years

2.  48400 years

3.  72600 years

4.  96800 years

Guessed #2

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The specific rate constant, k, for a reaction is 2.64x10^-2 s^-1 at 25 degrees C, and the activation energy is 74.0 kJ/mol. Calculate k at 75 degrees C.

1.  .932 s^-1

2.  83.9s^-1

3.  .266s^-1

4.  2.43s^-1

5.  1.92s^-1

My work, I really don’t know if I did this right….

T1 = 25 + 273 = 298 K
T2 = 75 + 273 = 348 K
ln(k1/k2) = (Ea/R) (1/T2 - 1/T1))
ln (k/2.64 x 10^-2 ) = (74000 / 8.3145) ( (1 / 298 )- (1 / 348) )

ln( k/2.64 x 10^-2 )= 4.29
e ^ 4.29 = 72.9664

k/2.64 x 10^-2 = 72.9664

K=1.92

=======================================

N2(g)+3H2(g)=2NH3(g)

If h2 disappears at a rate of .1 M/s then NH3 appears at a rate of……

1.  .067 M/s

2.  .15M/s

3.  .033 M/s

4.  .3 M/s

5.  .1 M/s

Guessed .067

==============================================

Which of the following reactions would you predict to have the largest orientation factor?

1  NH3 (g) + BCl3 (g) ->  H3N-BCl3 (g)

2  H (g) + Cl (g) ->  HCl (g)

3  NOF (g) + NOF (g)  ->  2NO (g) + F2 (g)

4  Br2 (g) + H2C=CH2 (g) ->  H2BrC-CBrH 2 (g)

5  All of these reactions should have nearly identical orientation factors.

My guess #2

==================================================

What is the vapor pressure of aqueous solution containing 10% ethylene glycol (62.067g/mol) at 25 c

PH2O=23.5 torr at 25 C

1.  25.1torr

2.  21.9torr

3.  23.5torr

4.  18.9torr

5.  .761 torr

My guesswork

Mass ethylene glycol = 10 g
moles = 10/ 62 = 0.161

mass water = 90 g
moles = 90 / 18 = 5

mole fraction water = 5 / 5 + 0.161 =0.969

p = 24.3 x 0.969 = 23.5 torr

======================================================

If the concentration of CO2 is 2.90 g of CO2 per 1.00 L of soft drink when bottled under 2.0 atm of CO2 pressure, what will be the concentration of the CO2 in the drink after it has been opened and left to come to equilibrium with the atmosphere which has a CO2 partial pressure of 3.0 x 10-4 atm?

a) 2.2 x 10-3 g CO2/L
b) 2.0 x 10-4 g CO2/L
c) 1.0 x 10-4 g CO2/L
d) 4.4 x 10-4 g CO2/L
e) 4.6 x 10-2 g CO2/L

I guessed d, I have no idea….

================================================

Which of the following statements about catalysts are false?
1  A catalyst lowers the reactions delta h.

2  A catalyst speeds up the rate of the reaction

3  A catalyst cannot make a nonspontaneous reaction spontaneous.
4  A catalyst increases the rate of both the forward and reverse reaction.

I guessed 3, no clue

=======================================================

2h2s+3o2=2so2+2h2o

Rate law =k[h2s]^2[o2]^2

What is overall order of reaction?

1

2

3

4

I put 4

2+2=4

(Top Tutor) Daniel C.
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School: University of Maryland
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