Consider the following equilibrium, mathrmCO(mathrmg) + 2mathrmH_2(mathrmg) rightleftharpoons mathrmCH_3mathrmOH(mathrmg) 0.1 mol of CO along with a catalyst is present in a 2mathrmdm^3 flask maintained at 500mathrmK. Hydrogen is introduced into the flask until the pressure is 5 bar and 0.04 mol of mathrmCH_3mathrmOH is formed. The mathrmK_p^0 is times 10^-3 (nearest integer). Given: mathrmR = 0.08mathrmdm^3cdottextbarcdotmathrmK^-1cdottextmol^-1 Assume only methanol is formed as the product and the system follows ideal gas behaviour.

Numerical Answer Type:
Enter a numerical value Answer: 74 to 74 +4 marks

Solution & Explanation

### Related Formula Ideal Gas equation layout for aggregate systems: P_texttotal cdot V = n_texttotal cdot RT Partial Pressure expression using mole fractions: p_i = X_i cdot P_texttotal ### Core Logic Let's tabulate equilibrium progress row-by-row: * Reaction matrix: beginarraylcccc & mathrmCO(g) & + & mathrm2H_2(g) & rightleftharpoons & mathrmCH_3OH(g) \\ t=0 & 0.1 & & a & & 0 \\ t_texteq & 0.1 - x & & a - 2x & & x endarray * Given x = 0.04mathrm~mol at equilibrium: - n_mathrmCO = 0.1 - 0.04 = 0.06mathrm~mol - n_mathrmCH_3OH = 0.04mathrm~mol * Determine total moles via system pressure (P = 5mathrm~bar, V = 2mathrm~L, T = 500mathrmK): 5 times 2 = n_texttotal times 0.08 times 500 implies n_texttotal = frac1040 = 0.25mathrm~mol * Find remaining unknown hydrogen moles: n_texttotal = 0.06 + n_mathrmH_2 + 0.04 = 0.25 implies n_mathrmH_2 = 0.15mathrm~mol ### Step 1: Calculate Kp Compute partial pressures using fractional allocation fractions (n_texttotal = 0.25): * p_mathrmCH_3OH = frac0.040.25 times 5 = 0.8mathrm~bar * p_mathrmCO = frac0.060.25 times 5 = 1.2mathrm~bar * p_mathrmH_2 = frac0.150.25 times 5 = 3.0mathrm~bar Substitute these pressures into the equilibrium expression: K_p = fracp_mathrmCH_3OHp_mathrmCO cdot (p_mathrmH_2)^2 = frac0.81.2 times 3^2 = frac0.810.8 = 0.07407 = 74.07 times 10^-3 Rounding to the nearest integer yields 74. ### Pattern Recognition Finding the total moles using the Ideal Gas Law from the final equilibrium pressure and volume cuts down steps, as it avoids explicitly computing the initial hydrogen amount 'a' first. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Equilibrium

More Equilibrium Previous-Year Questions — Page 4

Q46 jee_main_2025_24_jan_morning Chemical Equilibrium and Kp calculation
37.8 mathrm~g mathrm~N_2 mathrmO_5 was taken in a 1 mathrm~L reaction vessel and allowed to undergo the following reaction at 500 mathrm~K: 2 mathrm N _ 2 mathrm O _ 5 (mathrm g) ightarrow 2 mathrm N _ 2 mathrm O _ 4 (mathrm g) + mathrm O _ 2 (mathrm g) The total pressure at equilibrium was found to be 18.65 bar. Then, mathrmKp = \_ \_ \_ \_ times 10^-2 [nearest integer] Assume mathrmN_2mathrmO_5 to behave ideally under these conditions Given: mathrmR = 0.082 bar mathrmL \, mathrmmol^-1 \, mathrmK^-1
Numerical Answer. Answer: 962 to 962

Solution

### Related Formula P = fracnRTV quad textand quad K_p = frac(P_N_2O_4)^2 cdot P_O_2(P_N_2O_5)^2 ### Core Logic First, find the initial moles of N_2O_5 using its molar mass (108text g/mol): n_0 = frac37.8108 = 0.35text moles Using the ideal gas equation, compute the initial pressure (P_i): P_i = frac0.35 times 0.082 times 5001 = 14.35text bar Setting up the equilibrium partial pressures table: beginarraylcccc & 2N_2O_5(g) & rightleftharpoons & 2N_2O_4(g) & + & O_2(g) \\ textInitially: & 14.35 & & 0 & & 0 \\ textAt equilibrium: & 14.35 - 2P & & 2P & & P endarray The total pressure at equilibrium is given as: P_texttotal = (14.35 - 2P) + 2P + P = 14.35 + P = 18.65text bar P = 18.65 - 14.35 = 4.3text bar Now, calculate the equilibrium partial pressures for each component: - P_N_2O_5 = 14.35 - 2(4.3) = 5.75text bar - P_N_2O_4 = 2(4.3) = 8.6text bar - P_O_2 = 4.3text bar Substitute these partial pressures into the K_p expression: K_p = frac(8.6)^2 times 4.3(5.75)^2 = frac73.96 times 4.333.0625 approx 9.619 Expressing the result in the requested format (x times 10^-2): K_p = 961.9 times 10^-2 Rounding to the nearest integer yields **962**. ### Pattern Recognition Always calculate the initial pressure first using the ideal gas law (PV=nRT). This provides a clear baseline for tracking equilibrium partial pressures. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Equilibrium
Q30 jee_main_2025_28_jan_evening Solubility Product
Arrange the following in increasing order of solubility product: Ca(OH)_2,\ AgBr,\ PbS,\ HgS
  • A. PbS < HgS < Ca(OH)_2 < AgBr
  • B. HgS < PbS < AgBr < Ca(OH)_2
  • C. Ca(OH)_2 < AgBr < HgS < PbS
  • D. HgS < AgBr < PbS < Ca(OH)_2

Solution

### Related Formula The solubility product constant (K_sp) reflects the equilibrium position of a sparingly soluble salt in water. ### Core Logic Based on standard literature K_sp values at 298text K: - HgS: approx 4 times 10^-53 (extremely insoluble, Group IIB cation analysis) - PbS: approx 8 times 10^-28 (highly insoluble, Group IIA cation analysis) - AgBr: approx 5 times 10^-13 (sparingly soluble halide salt) - Ca(OH)_2: approx 5.5 times 10^-6 (moderately soluble base) ### Step 1: Arrangement Comparing these K_sp orders: 4 times 10^-53 < 8 times 10^-28 < 5 times 10^-13 < 5.5 times 10^-6 Hence, the correct increasing sequence is: HgS < PbS < AgBr < Ca(OH)_2. ### Pattern Recognition Sulphides of heavy transition metals like Hg^2+ and Pb^2+ have exceptionally small K_sp values compared to halides or hydroxides. Among sulphides, HgS is famously known to have one of the lowest solubility products found in inorganic qualitative analysis. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Equilibrium
Q jee_main_2025_29_jan_morning Degree of Dissociation and Equilibrium Constant
At temperature T, compound mathrmAB_2(g) dissociates as: mathrmAB_2(g) rightleftharpoons mathrmAB_(g) + frac12mathrmB_2(g) having a degree of dissociation x (x ll 1). The correct expression for x in terms of K_p and total pressure p is: x = left(frac2K_p^2pright)^1/3
  • A. sqrt[3]frac2K_pp
  • B. sqrt[4]frac2K_pp
  • C. sqrt[3]frac2K_p^2p
  • D. sqrtmathrmK_p

Solution

### Related Formula K_p = fracp_mathrmAB cdot p_mathrmB_2^1/2p_mathrmAB_2 ### Core Logic Consider the equilibrium reaction setup:
StatemathrmAB_2(g)rightleftharpoonsmathrmAB_(g)+frac12mathrmB_2(g)
Initial moles:100
Equilibrium moles:1 - xxfracx2
Total equilibrium moles: n_texttotal = 1 - x + x + fracx2 = 1 + fracx2 Since x ll 1, total moles n_texttotal approx 1 and (1 - x) approx 1. Partial pressures: p_mathrmAB_2 approx p p_mathrmAB approx x p p_mathrmB_2 approx fracx2 p Substituting into K_p: K_p = frac(x p) cdot left(dfracx p2right)^1/2p = x cdot left(fracx p2right)^1/2 = fracx^3/2 p^1/2sqrt2 Squaring both sides and solving for x: K_p^2 = fracx^3 p2 implies x^3 = frac2K_p^2p x = sqrt[3]frac2K_p^2p ### Pattern Recognition For Delta n_g = 0.5 involving degree of dissociation x ll 1, tracking total pressure approximations ensures an immediate analytical solution without full polynomial expansion. ### Chapter Mix Class 11 Chemistry: Chemical Equilibrium
Q90 jee_main_2024_01_february_morning Hydrolysis of Salts
K_a for CH_3COOH is 1.8 times 10^-5 and K_b for NH_4OH is 1.8 times 10^-5. The pH of ammonium acetate solution will be
Numerical Answer. Answer: 7 to 7

Solution

### Related Formula For a salt of weak acid and weak base (like ammonium acetate): mathrmpH = frac12 (mathrmpK_w + mathrmpK_a - mathrmpK_b) ### Core Logic Ammonium acetate (CH_3COONH_4) is a salt formed from a weak acid (CH_3COOH) and a weak base (NH_4OH). Given: K_a = 1.8 times 10^-5 K_b = 1.8 times 10^-5 Since K_a = K_b, taking the negative logarithm gives mathrmpK_a = mathrmpK_b. ### Step 1: Calculate pH mathrmpH = fracmathrmpK_w + mathrmpK_a - mathrmpK_b2 Substitute mathrmpK_a = mathrmpK_b: mathrmpH = fracmathrmpK_w2 At standard temperature (298 K), mathrmpK_w = 14. mathrmpH = frac142 = 7 ### Pattern Recognition If K_a = K_b for a weak acid-weak base salt, the hydrolysis of cation and anion perfectly balance out, making the resulting solution exactly neutral (pH = 7) regardless of the concentration of the salt. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Equilibrium
Q83 jee_main_2024_29_january_evening Equilibrium Constant Calculation
The following concentrations were observed at 500mathrmK for the formation of mathrmNH_3 from mathbfN_2 and mathrmH_2. At equilibrium: [mathrmN_2] = 2times 10^-2mathrmM, [mathrmH_2] = 3times 10^-2mathrmM and [mathrmNH_3] = 1.5times 10^-2mathrmM. Equilibrium constant for the reaction is ________.
Numerical Answer. Answer: 417 to 417

Solution

### Related Formula mathrmN_2(g) + 3mathrmH_2(g) rightleftharpoons 2mathrmNH_3(g) K_c = frac[mathrmNH_3]^2, [mathrmN_2][mathrmH_2]^3 ### Core Logic Substituting the given equilibrium concentrations into the equilibrium constant expression: K_c = frac(1.5 times 10^-2)^2, (2 times 10^-2) times (3 times 10^-2)^3 Evaluating the values step-by-step: K_c = frac2.25 times 10^-4, (2 times 10^-2) times (27 times 10^-6) ### Step 1: Final Arithmetic Integration K_c = frac2.25 times 10^-4, 54 times 10^-8 = frac2.25, 54 times 10^4 = 0.041666 times 10^4 approx 416.67 Rounding to the nearest integer yields **417**. ### Pattern Recognition Pay close attention to the cubic exponent in the denominator derived from the hydrogen stoichiometric coefficient (3). Small calculation errors here can significantly alter the result. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Chemical Equilibrium
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JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%) | JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%)