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Calculate the λ0m for Cl- ion from the data given below:
∧0m MgCl2 = 258.6 Scm2 mol-1 and λ0m Mg2+ = 106 Scm2 mol-1
Concept: Electrochemical Cells
Read the passage carefully and answer the questions that follow.
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The lead-acid battery represents the oldest rechargeable battery technology. Lead acid batteries can be found in a wide variety of applications including small-scale power storage such as UPS systems, ignition power sources for automobiles, along with large, grid-scale power systems. The spongy lead act as the anode and lead dioxide as the cathode. Aqueous sulphuric acid is used as an electrolyte. The half-reactions during discharging of lead storage cells are: Anode: \[\ce{Pb(s) + SO^{2-}_4 (aq) -> PbSO4 (s) + 2e-}\] Cathode: \[\ce{PbO (s) + 4H+ (aq) + SO^{2-}_4 (aq) + 2e- -> PbSO(s) + 2 H2O}\] There is no safe way of disposal and these batteries end - up in landfills. Lead and sulphuric acid are extremely hazardous and pollute soil, water as well as air. Irrespective of the environmental challenges it poses, lead-acid batteries have remained an important source of energy. Designing green and sustainable battery systems as alternatives to conventional means remains relevant. Fuel cells are seen as the future source of energy. Hydrogen is considered a green fuel. Problem with fuel cells at present is the storage of hydrogen. Currently, ammonia and methanol are being used as a source of hydrogen for fuel cell. These are obtained industrially, so add to the environmental issues. If the problem of storage of hydrogen is overcome, is it still a “green fuel?” Despite being the most abundant element in the Universe, hydrogen does not exist on its own so needs to be extracted from the water using electrolysis or separated from carbon fossil fuels. Both of these processes require a significant amount of energy which is currently more than that gained from the hydrogen itself. In addition, this extraction typically requires the use of fossil fuels. More research is being conducted in this field to solve these problems. Despite the problem of no good means to extract Hydrogen, it is a uniquely abundant and renewable source of energy, perfect for our future zero-carbon needs. |
Answer the following questions:
- How many coulombs have been transferred from anode to cathode in order to consume one mole of sulphuric acid during the discharging of lead storage cell?
- How much work can be extracted by using lead storage cell if each cell delivers about 2.0 V of voltage? (1 F = 96500 C)
- Do you agree with the statement – “Hydrogen is a green fuel.” Give your comments for and against this statement and justify your views.
OR
Imagine you are a member of an agency funding scientific research. Which of the following projects will you fund and why?
- safe recycling of lead batteries
- extraction of hydrogen
Concept: Batteries >> Secondary Batteries
Assertion (A): During electrolysis of aqueous copper sulphate solution using copper electrodes hydrogen gas is released at the cathode.
Reason (R): The electrode potential of Cu2+/Cu is greater than that of H+/H2.
Select the most appropriate answer from the options given below:
Concept: Electrolytic Cells and Electrolysis
Can we construct an electrochemical cell with two half-cells composed of ZnSO4 solution and zinc electrodes? Explain your answer.
Concept: Electrochemical Cells
The cell constant of a conductivity cell is 0.146 cm-1. What is the conductivity of 0.01 M solution of an electrolyte at 298 K, if the resistance of the cell is 1000 ohm?
Concept: Electrochemical Cells
How much electricity in terms of Faraday is required to produce 40.0 g of Al from molten Al2O3?
(Given: Molar mass of Aluminium is 27 g mol−1.)
Concept: Electrolytic Cells and Electrolysis
In a first order reaction x → y, 40% of the given sample of compound remains unreacted in 45 minutes. Calculate rate constant of the reaction.
Concept: Factors Influencing Rate of a Reaction
Sucrose decomposes in acid solution to give glucose and fructose according to the first order rate law. The half life of the reaction is 3 hours. Calculate fraction of sucrose which will remain after 8 hours.
Concept: Half Life Period of a Reaction
A reaction is second order in A and first order in B.
(i) Write the differential rate equation.
(ii) How is the rate affected on increasing the concentration of A three times?
(iii) How is the rate affected when the concentrations of both A and B are doubled?
Concept: Factors Influencing Rate of a Reaction
For a first order reaction, show that time required for 99% completion is twice the time required for the completion of 90% of reaction.
Concept: Half Life Period of a Reaction
(b) Rate constant ‘k’ of a reaction varies with temperature ‘T’ according to the equation:
`logk=logA-E_a/2.303R(1/T)`
Where Ea is the activation energy. When a graph is plotted for `logk Vs. 1/T` a straight line with a slope of −4250 K is obtained. Calculate ‘Ea’ for the reaction.(R = 8.314 JK−1 mol−1)
Concept: Temperature Dependence of the Rate of a Reaction
A first order reaction takes 40 minutes for 30% decomposition. Calculate t1/2 for this reaction. (Given log 1.428 = 0.1548)
Concept: Half Life Period of a Reaction
For a reaction: 
Rate = k
(i) Write the order and molecularity of this reaction.
(ii) Write the unit of k.
Concept: Factors Influencing Rate of a Reaction
For the first order thermal decomposition reaction, the following data were obtained:
Time / sec Totalpressure / atm
0 0.30
300 0.50
Calculate the rate constant
(Given: log 2 = 0.301, log3 = 0.4771, log 4 = 0.6021)
Concept: Factors Influencing Rate of a Reaction
The rate constant of a first order reaction increases from 4 × 10−2 to 8 × 10−2 when the temperature changes from 27°C to 37°C. Calculate the energy of activation (Ea). (log 2 = 0.301, log 3 = 0.4771, log 4 = 0.6021)
Concept: Temperature Dependence of the Rate of a Reaction
A first order reaction takes 23.1 minutes for 50% completion. Calculate the time required for 75% completion of this reaction.
(log 2 = 0.301, log 3 = 0.4771, log 4 = 0.6021)
Concept: Half Life Period of a Reaction
A reaction is second order with respect to a reactant. How is the rate of reaction affected if the concentration of the reactant is doubled?
Concept: Factors Influencing Rate of a Reaction
A reaction is first order in A and second order in B. How is the rate affected on increasing the concentration of B three times?
Concept: Factors Influencing Rate of a Reaction
A reaction is first order in A and second order in B. How is the rate affected when the concentrations of both A and B are doubled?
Concept: Factors Influencing Rate of a Reaction
What is the effect of adding a catalyst on Activation energy (Ea)
Concept: Temperature Dependence of the Rate of a Reaction
