HSC Science (Computer Science) १२ वीं कक्षा - Maharashtra State Board Important Questions

Answer in brief.

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.

An intensive property amongst the following is ______.

The change in internal energy in a reaction when 2kJ of heat is released by the system and 6 kJ of work is done on the system will be ______.

How many moles of electrons are required for reduction of 2 moles of Zn²⁺ to Zn?

Calculate enthalpy of formation of HCl if bond enthalpies of H₂, Cl₂ and HCl are 434 kJ mol^-1, 242 kJ mol^–1 and 431 kJ mol^–1 respectively.

Define the Enthalpy of sublimation.

Write the features of reversible processes.

Derive an expression for pressure-volume work.

Define the Enthalpy of vaporization.

Why work done in vacuum is zero?

Calculate the standard enthalpy of formation of liquid methanol from the following data:

1. \[\ce{CH3OH_{(l)} + \frac{3}{2} O_{2(g)} -> CO_{2(g)} + 2H2O_{(l)}}\]     ∆H° = – 726 kJ mol^–1
2. \[\ce{C_{(Graphite)} + O_{2(g)} -> CO_{2(g)}}\]          ∆_cH° = – 393 kJ mol^–1
3. \[\ce{H_{2(g)} + \frac{1}{2} O_{2(g)} -> H2O_{(l)}}\]          ∆_fH° = – 286 kJ mol^–1 

The enthalpy change for the chemical reaction \[\ce{H2O_{(s)} -> H2O_{(l)}}\] is called enthalpy of ______.

One mole of an ideal gas is expanded isothermally and reversibly from 10 L to 15 L at 300 K. Calculate the work done in the process.

Calculate the standard enthalpy of formation of CH₃OH_(l) from the following data:

1. \[\ce{CH3OH_{(l)} + 3/2 O2_{(g)} -> CO2_{(g)} + 2H2O_{(l)}ΔH^° = - 726 kJ mol^{-1}}\]
2. \[\ce{C_{(s)} + O2_{(g)} → CO2_{(g)}Δ_cH^° = – 393 kJ mol^{-1}}\]
3. \[\ce{H2_{(g)} + 1/2 O2_{(g)} -> H2O_{(l)}Δ_fH^° = - 286 kJ mol^{-1}}\]

Calculate the standard enthalpy of:

\[\ce{N2H_{4(g)} + H_{2(g)} -> 2NH_{3(g)}}\]

If ΔH⁰(N – H) = 389 kJ mol^–1, ΔH⁰(H – H) = 435 kJ mol^–1, ΔH⁰(N – N) = 159 kJ mol^–1.

Write the correct condition for spontaneity in terms of Gibbs energy.

Calculate the work done during the expansion of 2 moles of an ideal gas from 10 dm³ to 20 dm³ at 298 K in a vacuum.

2000 mmol of an ideal gas expanded isothermally and reversibly from 20 L to 30 L at 300 K, calculate the work done in the process (R = 8.314 JK^–1 mol^–1).

For a certain reaction ΔH⁰ is −224 kJ and ΔS⁰ is −153 J K⁻¹. At what temperature the change over from spontaneous to non-spontaneous will occur?