UNIT#06 CHEMICAL EQUILIBRIUM Flashcards
At equilibrium, the concentration of reactants and products are:
Constant
A statement which describes a reversible reaction:
Both forward and reverse reactions occur simultaneously under the same conditions
One mole of HI was sealed in a tube at 440°C till equilibrium is reached, HI was found to be 50% dissociated, and Kc for the reaction is:
0.25
For what value of Kc almost forward reaction is complete:
Kc = 10^30
1 mole of ethyl alcohol was treated with one mole of acetic acid at 25°C. 2/3 rd acid changes into ester at equilibrium. The equilibrium constant of the reaction will be:
4
At equilibrium concentration of SO2 is 2M, O2 is 2M and SO3 is 4M.
2SO2+O2→2SO3
What will be the Kc value of a given reaction?
2
In a reaction CO + 2H2 ➡CH3OH 🔺H=-92kj/mol.
Concentrations of hydrogen, carbon monoxide and methanol become constant at equilibrium, what will happen
The equilibrium state remains undisturbed
If the Kc value is very small then the equilibrium position will shift:
Towards left
The equilibrium expression for a reaction is Kc= X2/V(a-X), which is true for the reaction.
Decrease of pressure favoured forward reaction
For the reaction H2 + I2 ➡2HI. The equilibrium constant changes with:
Temperature
The correct relationship between Kc and Kp can be written as:
Kp=Kc(RT)🔺n
For the given reaction H2+I2➡2HI. the equilibrium concentration of H2, I2 and HI are 8,3 and 24 mole/dm^3 respectively. Kc of the reaction is:
24
For the following reaction in the gaseous phase:
CO+1/2O2 ➡CO2, Kc/Kp is:
(RT)1/2
In the reaction A2 + 4B2➡2AB such that 🔺H is negative, the formation of AB will be favoured at:
➡Low Temperature
➡High Pressure
N2 + 3H2➡2NH3
The forward reaction is favoured by:
Decreasing Temperature
In a given system, water and ice are in equilibrium, i the pressure is applied to the system then:
More ice is melted
If the temperature is increased for the following reaction, then it will go in:
N2 + 3H2➡2NH3 🔺H=-ive
Reverse reaction
In the Haber process, the equilibrium mixture contains ___ NH3 by volume
35%
The catalyst used in Haber’s process for the manufacture of NH3 is:
Fe(MgO, Al2O, SiO2)
The basic buffer solution is:
➡NH4OH
➡NH4Cl
Buffer action can be explained by all except:
SOlbulitiy Product
A basic buffer solution can be prepared by mixing:
Weak base and its salt with strong acid
The pH of the ideal buffer is
7
A certain buffer solution contains an equal concentration of X and HX. Ka for HX is 10^-8. The pH of the buffer is:
8
Which Henderson equation is correct:
➡pH = pKₐ - log([acid]/[salt]
➡pH = pKₐ + log([salt]/[acid]
➡pH = pKₐ - log([salt]/[acid]
For acidic buffer, pH < pKa if:
[salt] < [acid]
When HCl gas is passed through a saturated solution of rock salt, the solubility of NaCl
Decreases
An excess of silver nitrate is added to the aqueous barium chloride and the precipitate is removed by filtration. What are the main ions in the filtrate
Ag+ and NO3- and Ba+2 only
Ionization of KClO3 is suppressed by:
Adding KCl
If the ionic product is equal to Ksp, then the solution is:
Saturated
The solubility product is only applicable for those substances whose molar concentration is:
Equal to or less than 0.01
In a saturated solution of AgCl, the molar concentration of Ag+ and Cl=- is 1.0 x 10^-5 M each. What is the value of Ksp
1.0 x 10^-10
The molar solubility of sparingly soluble salt AB3 is “S” mol/dm^3, the corresponding solubility product Ksp is given in terms of Ksp by the reaction
S= (Ksp/27)1/4
Units of Kc for the following reaction is: H2 + O2 ➡2HI
No unit
If in AgCl solution, some salt of NaCl is added, AgCl will be precipitated due to:
Electrolyte
The formation of NH3 is a reversible and exothermic process, what will happen on cooling?
More products (NH3) will be formed
A buffer solution is that which resists/minimizes the change in:
pKb
The chemical substances, when dissolved in water, give “H” is called
Acid
The ‘pH’ of our blood is:
7.9
The value of equilibrium constant Kc for the reaction 2HF➡H2 + F2 is 10^-13 at 2000°C. Calculate the value of Kp for this reaction
10^-13
What will be the pH of a solution of NaOH with a concentration of 10^-3M
11
During the manufacture of nitric acid, nitric oxide is oxidized to nitrogen dioxide. This reaction is given to:
2NO + O2 ➡ 2NO2 🔺H=-114kJ/mol
According to Le Chatlier’s principle:
The reaction must be carried out at a low temperature
Which one of the following is the correct representation for Ksp?
AgCl ➡ Ag+ + Cl-
Ksp [Ag+1][Cl-1]
Human blood maintains its pH between:
7.35-7.55
The value of Ksp for the PbSO4 system at 25°C is equal to:
1.6 x 10^-8 mol2dm-6
For which of the following equilibrium reaction, Kc has no units;
CO + H2O ➡CO2 + H2
Ca(OH)2 is sparingly soluble having a solubility product value of 6.5 x 10^-6. What will be its solubility
1.17 x 10^-2
The product of the concentrations of each ion in a saturated solution of a sparingly soluble salt at 298K raised to the power of their relative concentrations is:
Ksp
Which of the following factors affect a reversible chemical reaction in accordance with Le-Chatlier’s principle?
➡Pressure
➡Temperature
➡Concentration
Which one of the following factors does not affect the equilibrium positions?
Catalyst
The Kc Unit for the reaction N2 + 3H2 ➡2NH3 are:
mole-2 dm+6
Which one of the following bases has the highest Kb value?
NaOH
What is the pH of 0.1M of HCl?
1
The pKa value of CH3COOH is 4.74, and the pH of an equimolar solution of acetic acid and sodium acetate is:
4.74
Does precipitation occur when the product of ionic concentration is?
Greater than Ksp
Kp = KC (RT) in the equation if 🔺n<0 then:
Kp < Kc
PKa values of some acids are given below choose the weaker acid.
H2SO4
(-3)
Consider the reversible reaction
N2 + 2NH3 ➡2NH3 + Heat
The yield of NH3 will be maximum at:
➡Low temperature
➡High pressure
Ice and water are in equilibrium with each other. By increasing the pressure the equilibrium will shift in:
Forward
For an equilibrium reaction;
2SO2 + O2 ➡ 2SO3
The forward reaction is exothermic, an increase in temperature shifts the equilibrium position towards the left because:
The concentrations of SO2 and O2 increase and the concentration of SO3 decreases as the temperature increases
Which of the following reaction has greater Kp than Kc (Kp > Kc)?
2NOCl ➡ 2NO + Cl2
The equation N2 + 3H2 ➡ 2NH3 represents:
Haber’s process
For a gaseous phase reaction, when a number of moles of reactants and products are equal:
The value of Kp and Kc is the same
Purification of table salt (NaCl) by passing HCl gas through its saturated aqueous solution is an example of;
Common ion effect
The conversion of nitrogen to ammonia or nitrogenous compounds is called:
Nitrogen Fixation
The reversible reaction is:
Non-Spontaneous
H2 + I2 ➡2HI relation between Kp and Kc for this reaction is:
Kp = Kc
Production of ammonia by the Haber process is made economical by using:
Le Chatlier’s principle
With different numbers of moles of reactants and products the volume of the system:
Changes
Kc and Kp have the same value when reactants and products have the same number o:
Moles
Reversible reactions are:
Non-spontaneous
Production of ammonia by Haber process is made commercial by using
Le Chatlier’s principle
According to Le Chatlier’s principle, exothermic reactions are favoured by:
Decrease in Temperature
Kp = Kc (RT)🔺, T stands for:
Absolute Temperature
Manufacturing of Ammonia by Haber’s process is an:
Exothermic Reaction
The equilibrium constant for ideal gases in terms of partial pressure is denoted by:
Kp
Classification of solids is based upon the arrangement of:
➡Molecules
➡Atoms
➡Ions
A very small value of Kc depicts:
Little Forward Reaction
The equilibrium constant is always written as a ratio o:
Products over reactants
At equilibrium the concentration of reactants and products are
Constant
Statement, which describes a reversible reaction
Both forward and reverse reaction occur simultaneously at the same time under same conditions
In a given system, water and ice are in equilibrium, if the pressure is applied to the system then
more ice is melted
If Kc value is small then equilibrium position will shift
towards left
Value of Kc for H2O at 25°C is
1×10-¹⁴ mol/dm3
One mole of HI was sealed in a tube heated at 440°C till equilibrium is reached, HI was found to be 50% dissociated, Kc for the reaction is
1
For what value of Kc, almost forward reaction is complete
Kc=10³⁰
One mole of ethyl alcohol was treated with one mole of acetic acid at 25°C. 2/3 of acid changes into Easter at equilibrium. The equilibrium constant of the reaction will be
4
In haber process, equilibrium mixture contains _________ NH3 by volume
35%
Catalyst used in haber process for manufacturing of NH3 is
Fe(MgO, Al2O, SiO2)
Which of the following is strongest conjugate base
C2H5O-
The conjugate base of H2PO4-¹ is
HPO4-²
Which of the following is a base according to bronsted lowery concept
I-¹
According to bronsted lowery concept, correct order of relatives strength of bases follows the order
OH- > CH3COO- > Cl-
pKa value of three acid A, B, C are 4.3, 3.3 and 5.5 respectively which represent correct order of strength
B > A > C
Select the pKa values of strongest acid from following
1
Which is correct statement
Ka × Kb = Kw
The Kw of water at 25°C is given by
10-¹⁴
At 90°C, pure water has (H3O+) is 10-⁶ mol/dm3. What is the value of Kw at 90°C
10-¹²
With increase in temperature ionic product of H2O
Increases
The pH of neutral water is 6.8 then the temperature of H2O is
More than 25°C
The value of Kw in an acidic aqueous solution at 298K is
10-¹⁴
Which statement is incorrect
pH and OH- are directly related to each other
Which of the following is not correct
pH= 1/log(H+)
H+ concentration of a solution is 1 mol/ dm3, its pH is
0
What will be the pH of 1 mol/dm3 of H2X, which is only 50% dissociated
0
What is the pH of 0.1M solution of weak acid having ionization constant Ka 10-⁷
4
The pH of 1M MOHsolution which is only 10% dissociated
13
Basic buffer solution is
NH4OH/NH4Cl
Buffer action can be explained by all except:
Common ion effect
Law of mass action
Le chateliers principle
Solubility product
Solubility product
pH of monoprotic acid is 3 at 25°C. The hydrogen ion concentration in the solution would be
0.001
A basic buffer solution can be prepared by mixing
Weak base and its salt with strong acid
pH of ideal buffer is
7
pH of 10-³ mole/dm3 of H2SO4 is
2.7
A certain buffer solution contains equal concentration of X and HX. Ka for HX is 10-⁸. The pH of buffer is
8
For acidic buffer, pH < pKa if
[Salt] < [acid]
If Ionic product is equal to Ksp then the solution is
Saturated
The solubility product is only applicable for those substance whose molar concentration is
Equal to or less than 0.01
In a saturated solution of AgCl, the molar concentration of Ag+ and Cl- is 1×10-⁵M each. What is the value of Ksp
1×10-¹⁰
The solubility product of AgCl is 2×10-¹⁰ mol2/dm6. The maximum concentration of Ag+ ions in the solution is
1.41×10^-5 mol/dm3
The molar solubility of sparingly soluble salt AB3 is S mol/dm3, the corresponding solubility product Ksp is given in term of Ksp by the reaction
S=(Ksp/27)¼
When HCl gas is passed through saturated solution of rock salt, the solubility of NaCl
Decreases
An excess of silver nitrate is added to the aqueous barium chloride and the precipitate is removed by filtration. what are main ions in the filtrate
Ag+ and NO3- and Ba+2 only
Ionization of KClO3 is suppressed by
Adding KCl
For the reaction, 2NH3 → N2 + 3H2
The Units of Kp will be:
(atm)^2
The rate of decrease in concentraion of reactants or that of increase in concentration of products is ___ at the beginning and ___ at the ending.
➡Faster
➡Slower
For the following reaction A + B ⇌ 2C + D. The equilibrium constant unit
mol dm^-3
For the reaction A + B ⇌ C + D one starts with 6 moles A and 7 moles B per dm^3. When equilibrium is attained, 4.5 moles o C is formed, what is the value of Kc for the reaction.
5.3
2HI ⇌ H2 + I2
For above reaction if Kc is 0.25, then Kp for this reaction will be:
0.25
Following is the condition of reversible reaction that is not affected by pressure (where Δn = number o moles of product - number of moles reactants)
Δn = 0
Find the Kc o following reaction if equilibrium concentrations of acetic acid, ethanol, ethyl acetate and water are 1.0 M, 1.0M, 2.0M and 2.0M respectively.
4
For the equilibrium 2O3 ⇌ 3O2
The value of Kc= 10^55 at 298 K .It indicates thate:
➡Forward reaction goes virtually to completion
➡O3 is unstable as compared to O2
➡O2 is more stable than O3
If ratio of concentration o products and that of reactants is greater than Kc then reaction will move:
Backward
If the value of Kc is very large for a reaction then the reacton is;
Almost complete
In ___ case increase in temperature and decrease in pressure favours the forward reaction:
PCl5 ⇌ PCl3 + Cl2
If number of moles of reactants are greater than products, then relationship between Kp and Kc is:
Kp < Kc
For the reaction 2HI ⇌ H2 + I2 the equilibrium constant is effected by change in;
Temperature
In which case , decrease of pressure favours forwards reaction
➡At low pressure, equilibirum will shift towards more number of moles
➡At high pressure, equilibirum will shift towards less number of moles
The equilibirum of gaseous reversible reaction that proceeds with decrease in number of moles will shift to right when
Pressure increases
In the following reaction the white ppt i.e. artificial milk (BiOCl) disappears when
BiCl3 + H2O ⇌ BiOCl + 2HCl
More HCl is added
Change in pressure is not favourable to the reactions having reactants and products in
➡Liquid Phase
➡Solid Phase
In an exothermic exothermic reversible reaction ___ tempearture will shift the equilibrium towards the forward direction.
Low
Which one will not affect both equilibrium position and equilibirum constant
Catalyst
When NH4Cl is added in NH4Oh solution then ionization of NH4OH
Decreases
If in AgCl solution ,some salt of NaCl is added, AgCl will be precipattated due to:
Common Ion Effect
Ionization of phenol can be decreased by adding:
Hydrochloric acid
Buffer solution is needed in;
➡Clinical Analysis
➡Soil Sciences
➡Microbiology
A buffer solution has equal volume 0.5M NH4OH and 0.5M NH4Cl.
The pKb of base is 4.74, pH of the solution is:
9.26
Buffer is a solution:
Which resists change in its pH
Select the buffer which is not acidic
NH4OH and NH4NO3
The solubility product of PbSO4 is 4 x 10^6 mol2. dm-6.
The maximum concentraion of Pb2 ions is;
2 x 10-3 mol.dm-3
An excess of aqueous silver nitrate is added to aqueous barium chloride and precipitate is removed by filtration. What are the main ions in the filtrate?
➡Ag+
➡Ba+2
➡NO3-1
For solubility product of solutions ,solubility of salt may be equal to or less then:
0.01M
Calculate the value of Kc or ammonia synthesis when the equilibirum concentraion o nitrogen, hydrogen and ammonia are 2M, 2M and 4M at 400°C
1.0 mol-2 dm6
2A + B ⇌ C + D
In this gaseous mixture, concentraion of all is doubled, then equilibirum constant bbecoems;
Remains the same
The concentrations of the reactants and products at equilibirum aere:
Constant
For which system the equilibirum constant Kc has unit of (concentration)^-1
2NO2 ⇌ N2O4
Appropriate units of Kp for the following reaction is:
PCl5 ⇌ PCl3 + Cl2
Torr
For which of the following reactions Kp>Kc
PCl5 ⇌ PCl3 + Cl2
For the reaction N2 + 3H2 ⇌ 2NH3
Which of the following relationship is correct?
➡Kc = Kp(RT)^2
➡Kp = Kc(RT)^-2
➡Kp = Kc / (RT)2
For which of the folllowing reactions Kc is greater than Kp
2NO + Cl2 ⇌ 2NOCl
Which is the correct relationship?
Kp = Kc (RT)^Δn
When no. of moles of reactants are equal to that of the prodcuts
Kp = Kc
For which of the following reactions Kp > Kc
PCl5 ⇌ PCl3 + Cl2
Decomposition of PCl5 is favoured by
PCl5 ⇌ PCl3 + Cl2
Increase in volume
Kc value indicates that the chemical reaction reaches farthest to the completon
10^15
Kc value for decomposition of HF is 10^-13 at 2000°C. it means that;
Reactants are more stable
Increasing the concentraion of reactants or decreasing the concentraion o the products moves reaction to_____ direction
Forward
The catalyst used for the synthesis of ammonia is:
➡Pieces of iron
➡MgO, Al2O3, SiO2
At very high pressure and low temperature, the rate of formation of NH3 is:
Low
Which statement about following equilibirum correct?
2SO2 + O2 ⇌ 2SO3
The value of Kp falls with the rise in temperature
If a buffer solution of higher pH than seven is to be made we use:
Weak base and its last with strong acid
A basic buffer solution can be preapared by mixing:
Weak base and its salt with strong bas
A buffer solution has equal volume 0.5M NH4OH and 0.5M NH4Cl. The pKb of base is 4.74. pH of the solution is;
9.26
In buffer solution containing a weak acid and its salt. The ratio of concentraion of salt to acid is increased tenfolds, then pH of solution will:
Increase by one unit
pH of buffer solution containing 0.1M CH3COOH and 1M CH3COONa
(pKa 4.74)
5.74
The solubility product of an ionic compound AB2 is 32 x 10^-3 mole3 . dm-. The maximum concentraion of A +2 ion is:
2 x 10^-3 mol.dm-3
