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

For a chemical reaction dS=0.035 kJ/k and dH=20kJ. At what temperature does the reaction turn nonspontaneous?

Prove that ΔH=ΔU+ΔnRT. what is the condition under which ΔU=ΔH?

300 M mol of perfect gas occupies 13 L at 320 K. Calculate the work done in joules when the gas expands-

(a) isothermally against a Constant external pressure of 0.20atm.

(b) isothermal and reversible process.

(c) into vaccum until the volume of gas is increased by 3L (R=8.314J mol^-1 K^-1)

One mole of a gas expands by 3L against a constant pressure of 3 atmosphere. Calculate the work done in -

(a) L.atmosphere

(b) Joules

(c) Calories

Derive the relation between `DeltaG^@`and equilibrium constant (K) for the reaction -

aA_bB ⇌ cC+dD.​

A system absorbs 640 J heat and does work of 260 J, the change in internal energy of the system will be

(a) +380J

(b) -380J

(c) +900J

(d) -900J

Which of the following pairs is an intensive property?

(A) Density, viscosity

(B) Surface tension, mass

(C) Viscosity, internal energy

(D) Heat capacity, volume

For a chemical reaction, A→ products, the rate of reaction doubles when the concentration of
‘A’ is increased by a factor of 4, the order of reaction is

(A) 2

(B) 0.5

(C) 4

(D) 1

Define the term ‘enthalpy’.

What will happen to the internal energy if work is done by the system?

Calculate ΔH° for the reaction between ethene and water to form ethyl alcohol from the
following data:

ΔcH° C₂H₅OH_(l) = -1368 kJ
ΔcH° C₂H_4(g) = -1410 kJ
Does the calculated ΔH° represent the enthalpy of formation of liquid ethanol?

55 L atm of work is obtained when 1.0 mole of an ideal gas is compressed isothermally from
a volume of 28.5 L to 18.5 L, the constant external pressure is

(A) 5.05 atm

(B) 5.5 atm

(C) 0.05 atm

(D) 0.55 atm

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