HSC Science (Electronics) इयत्ता १२ वी - Maharashtra State Board Question Bank Solutions for Chemistry

Pyrolusite ore is _______.

A 0.1 m solution of K₂SO₄ in water has a freezing point of –4.3°C. What is the value of van’t Hoff factor if K_f for water is 1.86 K kg mol^–1?

Answer the following in one or two sentences.

What is van’t Hoff factor?

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How is van’t Hoff factor related to degree of ionization?

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Which of the following solution will have higher freezing point depression and why?

i. 0.1 m NaCl

ii. 0.05 m Al₂(SO₄)₃

Answer the following in one or two sentences.

Which of the four colligative properties is most often used for molecular mass determination? Why?

Derive the relationship between the degree of dissociation of an electrolyte and van’t Hoff factor.

At 25 °C, a 0.1 molal solution of CH₃COOH is 1.35 % dissociated in an aqueous solution. Calculate the freezing point and osmotic pressure of the solution assuming molality and molarity to be identical.

A 0.15 m aqueous solution of KCl freezes at - 0.510 °C. Calculate i and osmotic pressure at 0 °C. Assume the volume of solution equal to that of water.

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.

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State second law of thermodynamics in terms of entropy.

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

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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?