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

Explain with diagram the boiling point elevation in terms of vapour pressure lowering.

A solution of citric acid C₆H₈O₇ in 50 g of acetic acid has a boiling point elevation of 1.76 K. If K_b for acetic acid is 3.07 K kg mol^-1, what is the molality of solution?

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?

Choose the most correct answer:

Which of the Na following is a buffer solution?

Select the most appropriate option.

The enthalpy of formation for all elements in their standard states is _______.

Answer the following in one sentence :

How are basic buffer solutions prepared?

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If the standard enthalpy of formation of methanol is –238.9 kJ mol^–1 then entropy change of the surroundings will be _______. 

Answer the following in one sentence :

Write one property of a buffer solution.

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Bond enthalpies of H–H, Cl–Cl, and H–Cl bonds are 434 kJ mol^–1, 242 kJ mol^–1, and 431 kJ mol^–1, respectively. Enthalpy of formation of HCl is _______.

Answer in brief.

Obtain the expression for work done in chemical reaction.

Answer the following in one sentence :

Classify the following buffers into different types :

CH₃COOH + CH₃COONa

Obtain the relationship between ΔH and ΔU for gas phase reactions.

Calculate the work done in the decomposition of 132 g of \[\ce{NH4NO3}\] at 100°C.

\[\ce{NH4NO3_{(s)} -> N2O_{(g)} + 2H2O_{(g)}}\]

State whether work is done on or by the system.

Answer the following question.

Calculate standard enthalpy of reaction,

Fe₂O_3(s) + 3CO_(g) → 2Fe_(s) + 3CO_2(g), from the following data.

Δ_f H°(Fe₂O₃) = - 824 kJ/mol,

Δ_f H°(CO) = - 110 kJ/mol,

Δ_f H°(CO₂) = - 393 kJ/mol

Answer the following question.

Calculate ΔU at 298 K for the reaction,

C₂H_4(g) + HCl_(g) → C₂H₅Cl_(g), ΔH = - 72.3 kJ

How much PV work is done?

Calculate the amount of work done in the

1) Oxidation of 1 mole HCl_(g) at 200 °C according to reaction.

4HCl_(g) + O_2(g) → 2Cl_2(g) + 2H₂O_(g)

2) Decomposition of one mole of NO at 300 °C for the reaction

2NO_(g) → N_2(g) + O_2(g)

Answer the following question.

When 6.0 g of O₂ reacts with CIF as per 

\[\ce{2ClF_{(g)} + O2_{(g)} -> Cl2O_{(g)} + OF2_{(g)}}\]

The enthalpy change is 38.55 kJ. What is the standard enthalpy of the reaction? (Δ_r H° = 205.6 kJ)

Calculate the standard enthalpy of formation of \[\ce{CH3OH_{(l)}}\] from the following data:

\[\ce{CH3OH_{(l)} + 3/2 O2_{(g)} -> CO2_{(g)} + 2H2O_{(l)} }\]; Δ_rH° = − 726 kJ mol^-1 

\[\ce{C_{(graphite)} + O2_{(g)} -> CO2_{(g)}}\]; Δ_cH° = −393 kJ mol⁻¹

\[\ce{H2_{(g)} + 1/2 O_{(g)} -> H2O_{(l)}}\]; Δ_fH° = −286 kJ mol⁻¹

Calculate the work done and comment on whether work is done on or by the system for the decomposition of 2 moles of NH₄NO₃ at 100 °C
NH₄NO_3(s) → N₂O_(g) + 2H₂O_(g)

Answer the following in brief.

Using the relationship ΔG° of cell reaction and the standard potential associated with it, how will you show that the electrical potential is an intensive property?