1. Highest pH will be recorded for which of the following solutions if they are equimolar
(a) AlCl3
(b) LiCl
(c) BeCl2
(d) BaCl2
Answer: (d)
Explanation
AlCl3 is made up of AlOH3 and HCl.
LiCl is made up of LiOH and HCl.
BeCl2 is made up of BeOH2 and HCl.
BaOH2 is strongest base among the given options thus have maximum pH.
Video Explanation
2. On increasing the concentration of reactants in a reversible reaction, then equilibrium constant will
(a) depend on the concentration
(b) increase
(c) unchanged
(d) decrease
Answer: (c)
Explanation
Increase in conc. of reactants will proceed the equilibrium in the forward direction giving more products. So that the equilibrium constant value remains constant and independent of concentration.
The magnitude of the equilibrium constant is not affected by the changes in concentrations of reactants and products. Hence, for a reversible reaction, if the concentrations of the reactants are doubled, then the equilibrium constant value remains the same.
Video Explanation
- Which gas is responsible for the depletion of the ozone layer?
(a) Carbon dioxide
(b) Methane
(c) Chlorofluorocarbon
(d) Sulfur dioxide
Answer: (c)
Explanation
Ozone depletion, gradual thinning of Earth’s ozone layer in the upper atmosphere caused by the release of chemical compounds
containing gaseous chlorine or bromine from industry and other human activities.
The thinning is most pronounced in the polar regions, especially over Antarctica. Ozone depletion is a major environmental problem because it increases the amount of ultraviolet (UV) radiation that reaches Earth’s surface, which increases the rate of skin cancer, eye cataracts, and genetic and immune system damage.
The Montreal Protocol, ratified in 1987, was the first of several comprehensive international agreements enacted to halt the production and use of ozone-depleting chemicals.
Video Explanation - For a specific reaction, which of the following statements can be made about K, the equilibrium constant?
(a) It always remains the same at different reaction conditions
(b) It increases if the concentration of one of the products is increased.
(c) It increases if the concentration of one of the reactants is increased
(d) It changes with changes in the temperature.
Answer: (d)
Explanation
YES It changes with changes in the temperature. For Equilibrium constant K, the value of equilibrium constant for a particular reaction is always constant depending upon the temperature of the reaction and is independent of the concentration of reactant or product with which we start or the directions from which equilibrium is approached. It also does not depend on the pressure. However, it depends on the temperature of the reaction.
Video Explanation - The pH of 10-3 mol dm-3 of an aqueous solution of H2SO4 is
(a) 3
(b) 2.7
(c) 2
(d) 1.5
Answer: (b)
Explanation
According the equation
H2SO4 —-> 2H^+ + SO4^-2 H2SO4[10^-3]
would ionize completely and produce 2 multiply H^+[10^-3] That is when apply PH means negative log of that value it will give 2.67.
Video Explanation
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- Which buffer solution comprising of the following has its pH value greater than 7?
(a) CH3COOH+CH3COONa
(b) HCOOH+HCOOK
(c) CH3COONH4
(d) NH4OH+NH4Cl
Answer: (d)
The pH value of a basic buffer is always greater than 7.Among the given options, NH4OH+NH4Cl is the only mixture which consists of a mixture of a weak base and its conjugated salt and thus, has a pH greater than 7.
Video Explanation - The rate of a chemical reaction tells us about
(a) the reactants taking part in the reaction
(b) the products formed in the reaction
(c) how slow or fast the reaction is taking place
(d) none of the above
Answer: (c)
Explanation
The rate of reaction or reaction rate is the speed at which reactants are converted into products. When we talk about chemical reactions, it is a given fact that rate at which they occur varies by a great deal. Some chemical reactions are nearly instantaneous, while others usually take some time to reach the final equilibrium.
Video Explanation - The average rate and instantaneous rate of a reaction are equal
(a) at the start
(b) at the end
(c) in the middle
(d) when two rates have a time interval equal to zero
Answer: (d)
Explanation
rav = Δx/ Δt
rinst = dx/dt
For rav=rinst, Δt→0 i.e. the interval becomes infinitesimally small . Thus, rinst i.e., (dx/ dt )= Δt→0 lim Δx/ Δt
Video Explanation - The rate constant of zero-order reactions has the unit
(a) s-1
(b) mol L-1 s-1
(c) L2 mol-2 s-1
(d) L mol-1 s-1
Answer: (b)
Video Explanation - when the rate of the reaction is equal to the rate constant, the order of the reaction is
(a) zero order
(b) first order
(c) second order
(d) third order
Answer: (a)
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- In the Haber process for the manufacture of ammonia the following catalyst is used
(a) Platinized asbestos
(b) Iron with molybdenum as a promoter
(c) Copper oxide
(d) Alumina
Answer: (b)
Explanation
The Haber Process is used in the manufacturing of ammonia from nitrogen and hydrogen, and then goes on to explain the reasons for the conditions used in the process. The process combines nitrogen from the air with hydrogen derived mainly from natural gas (methane) into ammonia. The reaction is reversible and the production of ammonia is exothermic.
N2(g)+3H2(g)−⇀ 2NH3(g)
with ΔH=-92.4 kJ/mol.
A flow scheme for the Haber Process looks like this:
General Conditions of the Process
The catalyst: The catalyst is actually slightly more complicated than pure iron. It has potassium hydroxide added to it as a promoter – a substance that increases its efficiency.
The pressure: The pressure varies from one manufacturing plant to another, but is always high. You cannot go far wrong in an exam quoting 200 atmospheres.
Recycling: At each pass of the gases through the reactor, only about 15% of the nitrogen and hydrogen converts to ammonia. (This figure also varies from plant to plant.) By continual recycling of the unreacted nitrogen and hydrogen, the overall conversion is about 98%.
Video Explanation - In the rate equation, when the concentration of reactants is unity then the rate is equal to?
a) specific rate constant
b) average rate constant
c) instantaneous rate constant
d) None of the above
Explanation
We can say that at a given temperature, rate is equal to the rate constant of reaction when concentration of the reactant in unity. Thus rate constant is also known as specific reaction rate.
Video Explanation - In the reaction 2A + B → A2B, if the concentration of A is doubled and that of B is halved, then the rate of the reaction will (PPSC 2020)?
(a) increase 2 times
(b) increase 4 times
(c) decrease 2 times
(d) remain the same
Answer: (a)
Video Explanation - Which of the following observations is incorrect about the order of a reaction??
(a) The stoichiometric coefficient of the reactants doesn’t affect the order
(b) Order of a reaction is always a whole number
(c) Order of reaction is the sum of power to express the rate of reaction to the concentration terms of the reactants.
(d) Order can only be assessed experimentally
Answer: (b)
Video Explanation - When the system A + B C + D is at equilibrium,?
The sum of the concentrations of A and B must equal the sum of
(a) the concentrations of C and D.
(b) the forward reaction has stopped.
(C) the reverse reaction has stopped.
(d) neither the forward nor the reverse reaction has stopped.
Answer: (d)
Video Explanation - Consider the following reversible reaction. In a 3.00 liter container, the following amounts are found in equilibrium at 400 oC: 0.0420 mole N2, 0.516 mole H2 and 0.0357 mole NH3. Evaluate Kc. N2(g) + 3H2(g) <–> 2NH3(g)?
(a) 0.202
(b) 16.0
(c) 1.99
(d) None of these
Answer: (c)
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- At 445oC, Kc for reaction is 0.020., 2HI(g) <—> H2(g) + I2(g) then, A mixture of H2, I2, and HI in a vessel at 445oC has the following concentrations: [HI] = 2.0 M, [H2] = 0.50 M and [I2] = 0.10 M, then Qc, is TRUE for?
(a) Qc = Kc; the system is at equilibrium.
(b) Qc is less than Kc; more H2 and I2 will be produced.
(c) Qc is less than Kc; more HI will be produced.
(d) Qc is greater than Kc; more H2 and I2 will be produced.
Answer: (b)
Video Explanation - Consider the equilibrium system:, 2ICl(s) <—-> I2(s) + Cl2(g), Which of the following changes will increase the total amount of of Cl2 that can be produced??
(a) Removing the Cl2 as it is formed
(b) Adding more ICl(s)
(c) Removing some of the I2(s)
(d) All of the above
Answer: (a)
Video Explanation - What is the equilibrium constant for a reaction that has a value of Go = -41.8 kJ at 100 degree??
(a) 1.01
(b) 7.1 x 105
(c) -5.87
(d) 1.4 x 10-6
Answer: (c)
Video Explanation - Which of following change will favour the formation of more HI in the given reaction, H2 + I2 <—–>2HI?
(a) Increasing pressure
(b) Decreasing pressure
(c) By adding more HI
(d) By adding more H2 and I2
Answer: (d)
Video Explanation - When pressure is applied to the given equilibrium ice water which of the following will happen?
(a) More ice will be formed
(b) More water will be formed
(c) Equilibrium will not be disturbed
(d) Water will formed
Explanation
When pressure is applied to an equilibrium system between ice and water, the phase transition temperature of ice reduces. Thus it leads to a disbalance in the equilibrium which then shifts more to its right. So, more of ice melts into water.
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1A 00:00:00 Start
- 0:08 Highest pH will be recorded for which of the following solutions if they are equimolar
- 1:27 On increasing the concentration of reactants in a reversible reaction, then equilibrium constant will
- 2:40 Which gas is responsible for the depletion of the ozone layer?
- 3:07 For a specific reaction, which of the following statements can be made about K, the equilibrium constant?
- 3:29 The pH of 10-3 mol dm-3 of an aqueous solution of H2SO4 is
- 4:05 Which buffer solution comprising of the following has its pH value greater than 7?
- 4:47 The rate of a chemical reaction tells us about
- 5:14 The average rate and instantaneous rate of a reaction are equal
- 6:01 The rate constant of zero-order reactions has the unit
- 6:23 when the rate of the reaction is equal to the rate constant, the order of the reaction is
- 6:41 In the Haber process for the manufacture of ammonia the following catalyst is used
- 7:48 In the rate equation, when the concentration of reactants is unity then the rate is equal to?
- 7:32 In the reaction 2A + B → A2B, if the concentration of A is doubled and that of B is halved, then the rate of the reaction will (PPSC 2020)?
- 7:57 Which of the following observations is incorrect about the order of a reaction??
- 9:03 When the system A + B C + D is at equilibrium,?
- 9:30 Consider the following reversible reaction. In a 3.00 liter container, the following amounts are found in equilibrium at 400 oC: 0.0420 mole N2, 0.516 mole H2 and 0.0357 mole NH3. Evaluate Kc. N2(g) + 3H2(g) <–> 2NH3(g)?
- 10:58 At 445oC, Kc for reaction is 0.020., 2HI(g) <—> H2(g) + I2(g) then, A mixture of H2, I2, and HI in a vessel at 445oC has the following concentrations: [HI] = 2.0 M, [H2] = 0.50 M and [I2] = 0.10 M, then Qc, is TRUE for?
- 12:48 Consider the equilibrium system:, 2ICl(s) <—-> I2(s) + Cl2(g), Which of the following changes will increase the total amount of of Cl2 that can be produced??
- 14:01 What is the equilibrium constant for a reaction that has a value of Go = -41.8 kJ at 100 degree??
- 14:31 Which of following change will favor the formation of more HI in the given reaction, H2 + I2 <—–>2HI?
- 15:26 When pressure is applied to the given equilibrium ice water which of the following will happen?
- 16:54 General Discussion
