HSC Science (Computer Science) इयत्ता १२ वी - Maharashtra State Board Important Questions

How will you determine molar mass of solute from osmotic pressure?

How will you determine molar mass of solute from osmotic pressure?

Write the condition of reverse osmosis.

Write the condition of reverse osmosis.

Henry's constant for \[\ce{CH3Br_{(g)}}\] is 0.159 mol dm⁻³ bar⁻¹ 25°C. Calculate its solubility in water at 25°C, if its partial pressure is 0.164 bar.

Define enthalpy of sublimation.

How is enthalpy of sublimation related to enthalpy of fusion and enthalpy of vaporization?

Calculate C-Cl bond enthalpy from following reaction:

CH₃Cl_(g) + Cl_2(g) → Ch₂Cl_2(g) + HCl_(g) ΔH° = -104KJ

If C-H, Cl-Cl and H-Cl bond enthalpies are 414, 243 and 431 KJ-Mol^-1 respectively.

Absolute entropies of solids, liquids and gases can be determined by

• Measuring heat capacity of substance at various temperatures
• Subtracting standard entropy of reactants from products
• Measuring vibrational motion of molecules
• Using formula ΔS° = S_T° - S_O°

Amongst the following identify the criterion for a process to be at equilibrium -

1. ΔG < 0
2. ΔG > 0
3. ΔS_total=0
4. ΔS < 0

Define the Enthalpy of fusion

Determine whether the reactions with the following ΔH and ΔS values are spontaneous or non-spontaneous. State whether the reactions are exothermic or endothermic.

(a) ΔH = -110kJ, ΔS = + 40JK^-1 at 400 K

(b) ΔH = + 40kJ, ΔS = -120JK^-1 at 250K

Write one statement of first law of thermodyamics and its mathematical expression.

For the reaction: Cl₂(g) → 2Cl(g), _______.

(A) ΔH is positive, ΔS is positive

(B) ΔH is positive, ΔS is negative

(C) ΔH is negative, ΔS is negative

(D) ΔH is negative, ΔS is positive

The equilibrium constant Kp for the reaction,

H_2(g) + I_2(g) → 2HI_(g) is 130 at 510 K. Calculate ΔG^o for the following reaction at the same temperature: 2HI_(g) → H_2(g) + I_2(g) [Given: R = 8.314 J K^-1 mol^-1 ]

If the enthalpy of vaporisation of water at 100^oC is 186.5 J.mol^-1, the entropy of vaporization will be_____________ .

(a) 4.0 J . K^-1. mol-¹                                               

(b) 3.0 J . K^-l.  mol^-1

(c) 1.5 J - K^-1. mol-¹                                             

(d) 0.5 J . K^-l. mol^-1

State and explain Hess’s law of constant heat summation.

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)