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NEET CHEMISTRYEquilibriumMedium

Question

For the reaction, CH4(g)+2O2(g)⇌CO2(g)+2H2O(l)CH_4(g) + 2O_2(g) \rightleftharpoons CO_2(g) + 2H_2O(l), ΔrH=−170 kJ mol−1\Delta_r H = -170 \text{ kJ mol}^{-1}. Which of the following statements is not true?

A

At equilibrium, the concentrations of CO2(g)CO_2(g) and H2O(l)H_2O(l) are not equal

B

The equilibrium constant for the reaction is given by Kp=[CO2][CH4][O2]K_p = \frac{[CO_2]}{[CH_4][O_2]}

C

Addition of CH4(g)CH_4(g) or O2(g)O_2(g) at equilibrium will cause a shift to the right

D

The reaction is exothermic

Step-by-Step Solution

Let us evaluate all the statements:

  1. The concentration of pure liquid water, H2O(l)H_2O(l), is constant (approx. 55.5 M) and its active mass is taken as unity. It will not be equal to the concentration of CO2(g)CO_2(g). Hence, this statement is true.
  2. The equilibrium constant KpK_p is expressed in terms of partial pressures, not molar concentrations. Also, the stoichiometric coefficient of O2O_2 is 2, so it should be squared. The correct expression is Kp=pCO2pCH4⋅pO22K_p = \frac{p_{CO_2}}{p_{CH_4} \cdot p_{O_2}^2}. Similarly, Kc=[CO2][CH4][O2]2K_c = \frac{[CO_2]}{[CH_4][O_2]^2}. The expression given in the option misses the square on O2O_2 and uses concentration brackets for KpK_p. Thus, this statement is not true.
  3. According to Le Chatelier's principle, adding reactants (CH4CH_4 or O2O_2) to a system at equilibrium will shift the equilibrium in the forward direction (to the right) to consume the added reactants. Thus, this statement is true.
  4. The enthalpy change of the reaction, ΔrH\Delta_r H, is negative (−170 kJ mol−1-170 \text{ kJ mol}^{-1}), which indicates that heat is released. Thus, the reaction is exothermic. This statement is true.

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Equilibrium. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYEquilibriumreactionrightleftharpoonsdeltarfollowingstatements

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Consider the following reaction: $\text{A}_2(g) + \text{B}_2(g) \rightleftharpoons 2\text{AB}(g)$. At equilibrium, the concentrations of $[\text{A}_2] = 3.0 \times 10^{–3} \text{ M}$; $[\text{B}_2] = 4.2 \times 10^{–3} \text{ M}$ and $[\text{AB}] = 2.8 \times 10^{–3} \text{ M}$. The value of $K_c$ for the above-given reaction in a sealed container at $527^\circ\text{C}$ is:

A.3.9
B.0.6
C.4.5
D.2
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Amongst the given options, which of the following molecules/ions acts as a Lewis acid?

A.$\text{OH}^-$
B.$\text{NH}_3$
C.$\text{H}_2\text{O}$
D.$\text{BF}_3$
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Boric acid is an acid because its molecule

A.contains replaceable H⁺ ion
B.gives up a proton
C.accepts OH⁻ from water releasing proton
D.combines with proton from water molecule
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The following solutions were prepared by mixing different volumes of NaOH and HCl of different concentrations. pH of which one of them will be equal to 1?

A.$60 \text{ mL } \frac{M}{10} \text{ HCl } + 40 \text{ mL } \frac{M}{10} \text{ NaOH}$
B.$55 \text{ mL } \frac{M}{10} \text{ HCl } + 45 \text{ mL } \frac{M}{10} \text{ NaOH}$
C.$75 \text{ mL } \frac{M}{5} \text{ HCl } + 25 \text{ mL } \frac{M}{5} \text{ NaOH}$
D.$100 \text{ mL } \frac{M}{10} \text{ HCl } + 100 \text{ mL } \frac{M}{10} \text{ NaOH}$
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The tendency of $BF_3$, $BCl_3$ and $BBr_3$ to behave as Lewis acid decreases in the sequence:

A.$BCl_3 > BF_3 > BBr_3$
B.$BBr_3 > BCl_3 > BF_3$
C.$BBr_3 > BF_3 > BCl_3$
D.$BF_3 > BCl_3 > BBr_3$
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A compound $\text{BA}_2$ has $K_{sp} = 4 \times 10^{-12}$. Solubility of this compound will be:

A.$10^{-3} \text{ mol/L}$
B.$10^{-4} \text{ mol/L}$
C.$10^{-5} \text{ mol/L}$
D.$10^{-6} \text{ mol/L}$
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What is the molarity of the saturated solution if the solubility product for a salt of type AB is $4 \times 10^{-8}$?

A.$2 \times 10^{-4} \text{ mol/L}$
B.$16 \times 10^{-16} \text{ mol/L}$
C.$2 \times 10^{-16} \text{ mol/L}$
D.$4 \times 10^{-4} \text{ mol/L}$
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In qualitative analysis, the metals of Group I can be separated from other ions by precipitating them as chloride salts. A solution initially contains $\text{Ag}^+$ and $\text{Pb}^{2+}$ at a concentration of $0.10 \text{ M}$. Aqueous $\text{HCl}$ is added to this solution until the $\text{Cl}^-$ concentration is $0.10 \text{ M}$. What will the concentration of $\text{Ag}^+$ and $\text{Pb}^{2+}$ at equilibrium? ($K_{sp}$ for $\text{AgCl} = 1.8 \times 10^{-10}$, $K_{sp}$ for $\text{PbCl}_2 = 1.7 \times 10^{-5}$)

A.$[\text{Ag}^+] = 1.8 \times 10^{-11} \text{ M}; [\text{Pb}^{2+}] = 1.7 \times 10^{-4} \text{ M}$
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