HSC Science (Electronics) 12th Standard Board Exam - Maharashtra State Board Important Questions for Chemistry

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?

Write the sign convention of work done during expansion of gas.

Calculate the time required to deposit 2.4 g of \[\ce{Cu}\], when 2.03 A of current passed through \[\ce{CuSO4}\], solution. (At. mass of \[\ce{Cu}\] = 63.5 g mol⁻¹)

Define Intensive property.

Define Adiabatic process.

Calculate the standard enthalpy of combustion of methane if the standard enthalpy of formation of methane, carbon dioxide and water are −74.8, −393.5 and −285.8 kJmol⁻¹ respectively.

How much electricity in terms of Faraday is required to produce 40.0 g of Al from molten Al₂O₃?

(Given: Molar mass of Aluminium is 27 g mol⁻¹.)

Explain a graphical method to determine activation energy of a reaction.

In a first order reaction x → y, 40% of the given sample of compound remains unreacted in 45 minutes. Calculate rate constant of the reaction.

A → B is a first order reaction with rate 6.6 × 10^-5m-s^-1. When [A] is 0.6m, rate constant of the reaction is

• 1.1 × 10^-5s^-1
• 1.1 × 10^-4s^-1
• 9 × 10^-5s^-1
• 9 × 10^-4s^-1