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JEE Main 201910 JanuaryEvening Shift
Exam
JEE Main
Year
2019
Date
10 January
Shift
Evening Shift
Subject
Chemistry
Chapter
Chemical Equilibrium

JEE Main 2019 · 10 January · Evening Shift · Chemistry · Chemical Equilibrium

5 .1 g NH _ 4 SH is introduced in 3 .0 L evacuated flask at 327 ^ o...

5.1gNH4SH5 .1 g{NH}_{4}SH is introduced in 3.0L3 .0 L evacuated flask at 327oC{327}^{o}C . 3030 % of the solid NH4SH{NH}_{4}SH is decomposed to NH3andH2S{NH}_{3} and {H}_{2}S as gases. The KP{K}_{P} of the reaction at 327oC{327}^{o}C is

(R=0.082Latmmol−1K−1,MolarmassofS=32gmol−1,MolarmassofN=14gmol−1)\left(R = 0 .082 Latm{mol}^{- 1}{K}^{- 1}, MolarmassofS = 32g{mol}^{- 1}, MolarmassofN = 14g{mol}^{- 1}\right)

Options

  1. A0.242atm20 .242 {atm}^{2}
  2. B0.242×10−4atm20 .242 \times {10}^{- 4}{atm}^{2}
  3. C1×10−4atm21 \times {10}^{- 4}{atm}^{2}
  4. D4.9×10−3atm24 .9 \times {10}^{- 3}{atm}^{2}

Correct answer

A. 0.242atm20 .242 {atm}^{2}

Step-by-step solution

NH4SH(s)⇌NH3(g)+H2S(g){NH}_{4}SH\left(s\right) ⇌ {NH}_{3}\left(g\right) + {H}_{2}S\left(g\right)

Number of moles=5.151=0.1mol= \dfrac{5 .1}{51} = 0 .1 mol

NH4SH{NH}_{4}SH NH3{NH}_{3} H2S{H}_{2}S

Initial

concentration

0.1mol0 . 1mol 00 00

Equilibrium

concentration

0.1(1−α)0 . 1\left(1 - \alpha\right) 0.1α0 . 1\alpha 0.1α0 . 1\alpha



\left(\alpha = 30% = 0 .3\right) =Degreeofdissociation<br/><br/>So,numberofmolesatequilibrium,</p><p>[NH3]=Degree of dissociation<br /><br />So, number of moles at equilibrium,</p><p>\left[{NH}_{3}\right] =\left[{H}_{2}S\right] = 0 . 1 \times 0 . 3 = 0 . 03</p><p>[NH4SH]</p><p>\left[{NH}_{4}SH\right] is not considered as it is a solid.

Kc=[NH3][H2S]{K}_{c} = \left[{NH}_{3}\right]\left[{H}_{2}S\right]

Kc=[0.033][0.033]=10−4{K}_{c} = \left[\dfrac{0 . 03}{3}\right]\left[\dfrac{0 . 03}{3}\right] = {10}^{- 4}

Kp=10−4(0.082×600)2{K}_{p} = {10}^{- 4}{\left(0 . 082 \times 600\right)}^{2}

{K}_{p} = 0 .242 {atm}^{2}

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