CHEMICAL EQUILIBRIUM QUIZ-7

CHEMISTRY CHEMICAL EQUILBRIUM QUIZ-7

Dear Readers,

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Q1. For the system; 3A+2B⇌C, the expression for equilibrium constant is

•  ([A]³[B]²)/[C]
•  [C]/([A]³[B]²)
•  [3A][2B]/[C]
•  [C]/[3A][2B]

Solution
b)Equilibrium constant for the reaction, 3A+2B⇌C, is K=([C])/([A]³ [B]² )

Q2.At 600℃,K_p for the following reaction is 1 atm.
X(g)⇌Y(g)+Z(g)
At equilibrium, 50% of X(g) is dissociated. The total pressure of the equilibrium system is p atm.
What is the partial pressure (in atm) of X(g) at equilibrium?

•   1
•  4
•  2
•  0.5

Solution
(a) X(g) ⇌ Y(g) Z(g)
Initial 1 0 0
At equilibrium 0.5 0.5 0.5
Partial pressure 0.5/1.5 p 0.5/1.5 p 0.5/1.5 p
∵ K_p (p_Y.p_Z)/p_x
1 (p/3 p/3)/(p/3)
p 3 atm
Partial pressure of X p/3 3/3 1 atm.

Q3.  A chemical reaction A⇌B is said to be at equilibrium when:

•  Complete conversion of A to B has taken place
•  Conversion of A to B is only 50% complete
•  Only 10% conversion of A to B has taken place
•  The rate of transformation of A and B is just equal to the rate of transformation of B to A in the system

Solution
d) A chemical equilibrium is the state when concentration of reactants and products do not change with time. It is attained when rate of forward reaction becomes equal to rate of backward reaction.

Q4. As the temperature increases, the pH of a KOH solution

•  Will decrease
•  Will increase
•  Remains constant
•  Depends upon the concentration of KOH solution

Solution
b)

Q5.Aqueous solution of sodium cyanide is

•  Acidic
•  Amphoteric
•  Basic
•  Neutral

Solution
 c) Aqueous solution of NaCN is basic because it is a salt of strong base and weak acid

Q6.For the reaction, N₂+3H₂⇌2NH₃ at 5000C, the value of K_p is 1.44 × 10-5.
What will be the value of K_p at low pressure where the gases are behaving almost ideally?

•  1.44 × 10^-5
•  (0.082 × 773)²× 1.44 × 10^-5
•  1.44 × 10_-5×(0.082 × 500)²
•  1.44 × 10^-5× (0.082 × 773)³

Solution
a) K_p is independent of pressure.

Q7.Which is not amphoteric?

•   HSO₄^-
•   HCO₃^-
•  H₂PO₄^-
•  HCOO^-

Solution
(d) HCOO_- is base having conjugate acid HCOOH (a monobasic acid).

Q8.What is [H⁺] in mol/L of a solution that is 0.20 M in CH₃COONa and 0.1 M in CH₃COOH? K_a for CH₃COOH is 1.8×10^-5.

•   3.5×10^-4
•  1.1×10^-5
•  1.8×10^-5
•  9.0×10^-6

Solution
d) pH=pK_a+log⁡[Conjugate base]/[Acid] =5.045 ∴ [H⁺]=9.0×10^-6.

Q9.The K_sp for Cr(OH)₃ is 1.6 10³⁰.The molar solubility of this compound in water is:

•  (1.6 10³⁰)^1/2
•   (1.6 10³⁰)^1/4
•  (1.6 10³⁰⁄27^1/4
•  (1.6 10³⁰)⁄27

Solution
c) Let molar solubility of Cr(OH)_]₃=s mol L^-1 Cr(OH)₃ (s)⇌Cr^(3+) (aq)+3OH^- (aq) s 3s K_sp=1.6×10^-30=[Cr³⁺] [OH^- ]³ =(s) (3s)³=27s⁴ ∴ s⁴=(1.6×10^-30)/27

Q10. For the reaction, 2A(g)⇌3C(g)+D(s), the value of K_c will be equal to

•  K_p(RT)
•   K_p⁄RT
•  =K_p
•  None of these

Solution
b) 2A(g)⇌3C(g)+D(s) For this reaction, ∆n_g=3-2=1 ∴ K_p=K_c(RT)¹ or K_c=K_p/RT

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