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

Calculate the standard enthalpy of combustion of CH₃COOH(l) from the following data:

`Delta_fH^@(CO_2)=-393.3 kJ mol^-1`

`Delta_fH^@(H_2O)=-285.8 kJ mol^-1`

`Delta_fH^@(CH_3COOH)=-483.2 kJ mol^-1`

Distinguish between isothermal process and adiabatic process.

No machine has an efficiency unity', is stated in-

(a) first law of thermodynamics

(b) second law of thermodynamics

(c) third law of thermodynamics

(d) Hess' law of constant heat summation

Write chemical reactions involved in Van Arkel method for refining Titanium

Explain the relationship between Gibb's standard energy change of the reaction and equilibrium constant.

Calculate the standard enthalpy of the reaction, 2C(graphite) + 3H_2(g) → C₂H_6(g), ΔH° = ?

From the following ΔH° values

a) `C_2H_6(g) + 7/2 O_2(g) -> 2CO_2(g) + 3H_2 O(l)`.  ΔH° = -1560kJ

b) `H_2(g) + 1/2 O_2 (g) -> H_2O(l)`  ΔH° = -285.8kJ

c) C(graphite) + O₂(g) -> CO₂(g). ΔH° = -393.5kJ

Write applications of standard molar entropy°.

For a certain reaction, ∆H = − 50 kJ and ∆S = − 80 J K^-1, at what temperature does the
reaction turn from spontaneous to non-spontaneous?

(A) 6.25 K

(B) 62.5 K

(C) 625 K

(D) 6250 K

Calculate ∆H° for the following reaction:

2H₃BO_3(aq) → B2O_3(s) + 3H₂O_(l)

a) H₃BO_3(aq) → HBO_2(aq) + H₂O_(l) , ∆`H_1^@` = − 0.02 kJ

b) H₂B₄O_7(s) → 2B₂O_3(s) + H₂O_(l) , ∆`H_2^@` = 17.3 kJ

c)H₂B₄O_7(s) + H₂O_(l) → 4HBO_2(aq), ∆`H_3^@` = − 11.58 kJ

What are the conditions for spontaneous and non-spontaneous reactions in terms of free
energy change?

What is the action of heat on potassium permanganate?

Derive the equation : W = - P_extAV

The process in which the value of ΔU = 0 is __

Give two uses of the Third law of thermodynamics.

Calculate the internal energy at 298K for the formation of one mole of ammonia, if the enthalpy change at constant pressure is – 42.0 kJ mol^-1.

(Given: R = 8.314 J K^-1 mol^-1)

Define Enthalpy of vaporization

A system absorbs 6 kJ of heat and does 1.5 kJ of work on its surroundings. The change in internal energy is __________.

Write the conditions for maximum work done by the system.

Calculate the work done in the following reaction at 50°C. State whether work is done on the system or by the system.
`"SO"_2("g") + 1/2"O"_(2("g")) rightarrow "SO"_(3("g"))`

The standard enthalpy of combustion of formaldehyde Δ₀H⁰ = -571 kJ. How much heat will be evolved in the formation of 22 g of CO₂?