Question

16) How many half-lives are required for the concentration of reactant to decrease to 3.1% of its original value? A) 2 B) 3 C) 1 D) 5 E) 2.75 17) Calculate the Ksp for silver sulfite if the solubility in pure water is 4.6 x 10-3 g/L. A) 4.8 x 10-10 B) 2.4 x 10-10 91.5 * 10-14 D) 3.8 x 10-15 - 18) Which of the following statements are TRUE? A) The equilibrium constant for the forward reaction is equal to the equilibrium constant for the reverse reaction. B) Dynamic equilibrium occurs when the rate of the forward reaction equals the rate of the reverse reaction. C) Dynamic equilibrium indicates that the amount of reactants and products are equal. D) A reaction quotient (Q) larger than the equilibrium constant (K) means that the reaction will favor the production of more products. E) All of the above are true.

Answer 1

Let initial mass = 100 g
final mass = 3.1 g
And n be the number of half life

Initial mass/final mass = [2}^n

100/ 3.1 =[2}^n

Then n=5

option D
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Ag2SO3 ---> 2Ag+ + SO32-
given solubility = 4.6x10^-3 g/L convert this to mols/L,by dividing with molar mass
4.6x10^-3 g/L/295.80 mols/g = 0.01555 x10^-3 mols/L
Ksp = [Ag}^2{SO32-}
=[ 2*0.01555 x10^-3 mols/L]^2*0.01555 x10^-3 mols/L

= 1.5 x10^-5+-3+-6 = 1.5 x10^-14
Ksp = 1.5 x10^-14
option C
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18)
correct statements are
B) Dynamic equilibrium occurs when rate of forward reaction = rate of reverse reaction

Only one statement is correct
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