HSC Science (Electronics) 12th Standard Board Exam - Maharashtra State Board Question Bank Solutions

Answer the following in one or two sentences.

A solution concentration is expressed in molarity and not in molality while considering osmotic pressure. Why?

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What are isotonic and hypertonic solutions?

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A solvent and its solution containing a nonvolatile solute are separated by a semipermeable membrane. Does the flow of solvent occur in both directions? Comment giving a reason.

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The osmotic pressure of CaCl₂ and urea solutions of the same concentration at the same temperature are respectively 0.605 atm and 0.245 atm, calculate van’t Hoff factor for CaCl₂.

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Explain reverse osmosis.

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How molar mass of a solute is determined by osmotic pressure measurement?

An aqueous solution of a certain organic compound has a density of 1.063 g mL^-1 , osmotic pressure of 12.16 atm at 25 °C and a freezing point of 1.03 °C. What is the molar mass of the compound?

Select the most appropriate option.

Which of the following reactions is exothermic?

Answer the following in one or two sentences.

What is standard state of a substance?

Answer in brief.

How will you calculate reaction enthalpy from data on bond enthalpies?

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What is the standard enthalpy of combustion? Give an example.

Answer the following in one sentence :

The dissociation of H₂S is suppressed in the presence of HCl. Name the phenomenon.

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How much heat is evolved when 12 g of CO reacts with NO₂? The reaction is:

4CO_(g)  2NO_2(g) → 4CO_2(g) + N_2(g), Δ_rH° = - 1200 kJ

Answer the following question.

State Hess’s law of constant heat summation. Illustrate with an example. State its applications.

Answer the following :

The dissociation of HCN is suppressed by the addition of HCl. Explain.

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Calculate Δ_rH° for the following reaction at 298 K:

1) 2H₃BO_3(aq) → B₂O_3(s) + 3H₂O_(l), Δ_rH° = + 14.4 kJ

2) H₃BO_3(aq) → HBO_2(aq) + H₂O_(l), Δ_rH° = - 0.02 kJ

3) H₂B₄O_7(s) → 2B₂O_3(s) + H₂O_(l), Δ_rH° = + 17.3 kJ

Calculate the total heat required

a) to melt 180 g of ice at 0 °C

b) heat it to 100 °C and then

c) vapourise it at that temperature.

[Given: Δ_fusH° (ice) = 6.01 kJ mol^-1 at 0 °C, Δ_vapH° (H₂O) = 40.7 kJ mol^-1 at 100 °C, Specific heat of water is 4.18 J g^-1 K^-1]

The enthalpy change for the reaction, \[\ce{C2H4_{(g)} + H2_{(g)} -> C2H6_{(g)}}\] is −620 J when 100 mL of ethylene and 100 ml of \[\ce{H2}\] react at 1 bar pressure. Calculate the pressure volume type of work and ΔU for the reaction.

Answer the following :

Sulfides of the cation of group II are precipitated in acidic solution (H₂S + HCl) whereas sulfides of cations of group IIIB are precipitated in the ammoniacal solution of H₂S. Comment on the relative values of the solubility product of sulfides of these.

Answer the following :

The solubility of a sparingly soluble salt gets affected in the presence of a soluble salt having one common ion. Explain.