HSC Science (Electronics) १२ वीं कक्षा - Maharashtra State Board Question Bank Solutions

In which of the following, entropy of the system decreases?

Answer the following in one or two sentences.

State whether ΔS is positive, negative or zero for the reaction 2H_(g)  →  H_2(g). Explain.

Answer the following in one or two sentences.

State second law of thermodynamics in terms of entropy.

Answer the following in one or two sentences.

If the enthalpy change of a reaction is ∆H how will you calculate the entropy of surroundings?

Answer the following in one or two sentences.

Comment on the spontaneity of reactions for which ∆H is positive and ∆S is negative.

Obtain the relationship between ∆G° of a reaction and the equilibrium constant.

Answer in brief.

What is entropy? Give its units.

Answer the following question.

Although ΔS for the formation of two moles of water from H₂ and O₂ is –327J K^–1, it is spontaneous. Explain.
(Given ΔH for the reaction is –572 kJ).

Answer the following question.

Obtain the relation between ΔG and `triangle "S"_"total"`. Comment on the spontaneity of the reaction.

For a certain reaction ΔH° = 219 kJ and ΔS° = –21 J/K. Determine whether the reaction is spontaneous or nonspontaneous.

Answer the following question.

Determine whether the following reaction is spontaneous under standard state conditions.

2H₂O_(l) + O_2(g) → 2H₂O_2(l)

if ΔH° = 196 kJ, ΔS° = –126 J/K, does it have a cross-over temperature?

Answer the following in one or two sentences.

Write the Arrhenius equation and explain the terms involved in it.

Explain with the help of the Arrhenius equation, how do the rate of reaction changes with temperature.

Answer the following in brief.

How will you determine activation energy graphically using the Arrhenius equation?

Answer the following in brief.

Explain graphically the effect of temperature on the rate of reaction.

Solve

The energy of activation for a first-order reaction is 104 kJ/mol. The rate constant at 25°C is 3.7 × 10^–5 s ^–1. What is the rate constant at 30°C? (R = 8.314 J/K mol)

Solve

What is the energy of activation of a reaction whose rate constant doubles when the temperature changes from 303 K to 313 K?

The rate constant of a reaction at 500°C is 1.6 × 10³ M⁻¹ s⁻¹. What is the frequency factor of the reaction if its activation energy is 56 kJ/mol?

The rate constant for the first-order reaction is given by log₁₀ k = 14.34 – 1.25 × 10⁴ T. Calculate activation energy of the reaction.

Solve

What fraction of molecules in a gas at 300 K collide with an energy equal to the activation energy of 50 kJ/mol?