HSC Science (Electronics) १२ वीं कक्षा - Maharashtra State Board Important Questions

Draw labelled diagram of H₂ – O₂ fuel cell.

For a certain reaction ΔH⁰ is −224 kJ and ΔS⁰ is −153 J K⁻¹. At what temperature the change over from spontaneous to non-spontaneous will occur?

Write the sign convention of work done during expansion of gas.

Calculate the time required to deposit 2.4 g of \[\ce{Cu}\], when 2.03 A of current passed through \[\ce{CuSO4}\], solution. (At. mass of \[\ce{Cu}\] = 63.5 g mol⁻¹)

Define Intensive property.

Define Adiabatic process.

Calculate the standard enthalpy of combustion of methane if the standard enthalpy of formation of methane, carbon dioxide and water are −74.8, −393.5 and −285.8 kJmol⁻¹ respectively.

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.)

Explain a graphical method to determine activation energy of a reaction.

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.

A → B is a first order reaction with rate 6.6 × 10^-5m-s^-1. When [A] is 0.6m, rate constant of the reaction is

• 1.1 × 10^-5s^-1
• 1.1 × 10^-4s^-1
• 9 × 10^-5s^-1
• 9 × 10^-4s^-1

The integrated rate equation for first order reaction is A → products

The rate constant for a first order reaction is 100 s^–1. The time required for completion of 50% of reaction is _______.

(A) 0.0693 milliseconds

(B) 0.693 milliseconds

(C) 6.93 milliseconds

(D) 69.3 milliseconds

The Arrhenius equation is_________________ .

(a)`k=Ae^(RT/E_a)`                                                    

(b)`A=ke^(-E_a/(RT))`

(c)`k=Ae^(-(RT)/E_a)`

(d)`k=Ae^(-E_a/(RT))`

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.

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?

For a first order reaction, show that time required for 99% completion is twice the time required for the completion of 90% of 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 E_a 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 ‘E_a’ for the reaction.(R = 8.314 JK⁻¹ mol⁻¹)

 A first order reaction takes 40 minutes for 30% decomposition. Calculate t_1/2 for this reaction. (Given log 1.428 = 0.1548)

What is pseudo first order reaction? Give one· example of it.