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

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?

Answer in brief.

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.

Answer the following question.

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.

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

Answer the following in brief.

Why do the cell potential of lead accumulators decrease when it generates electricity? How the cell potential can be increased?

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Write the electrode reactions and net cell reaction in NICAD battery.

Answer the following in one or two sentences.

Why all collisions between reactant molecules do not lead to a chemical reaction?

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What is the activation energy of a reaction?

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Write the electrode reactions when lead storage cell generates electricity. What are the anode and cathode and write the electrode reactions during its recharging?

What are anode and cathode for Leclanche’ dry cell?

Answer the following in brief.

What are the requirements for the colliding reactant molecules to lead to products?

Write the reaction of conc. H₂SO₄ with sugar.