Science (English Medium) कक्षा १२ - CBSE Important Questions

Give the truth table and circuit symbol for NAND gate

Calculate the freezing point of a solution containing 60 g of glucose (Molar mass = 180 g mol^–1) in 250 g of water. (K_f of water = 1.86 K kg mol^–1)

Give reasons for the following:

Measurement of osmotic pressure method is preferred for the determination of molar masses of macromolecules such as proteins and polymers.

Give reasons for the following :

Aquatic animals are more comfortable in the cold water than in warm water.

Give reasons for the following

Elevation of the boiling point of 1 M KCl solution is nearly double than that of 1 M sugar solution.

An element 'X' (At. mass = 40 g mol^-1) having f.c.c. the structure has unit cell edge length of 400 pm. Calculate the density of 'X' and the number of unit cells in 4 g of 'X'. (N_A = 6.022 × 10²³ mol^-1)

Write the cell reaction and calculate the e.m.f of the following cell at 298 K:

`Sn(s) | Sn^(2+) (0.004 M) || H^(+) (0.020 M) | H_2 (g) ("1 bar") | Pt(s)`

(Given: `E_(Sn^(2+)"/"Sn)^0 = -0.14` V)

Give reasons On the basis of E° values, O₂ gas should be liberated at anode but it is Cl₂ gas which is liberated in the electrolysis of aqueous NaCl.

Give reasons Conductivity of CH₃COOH decreases on dilution.

For the reaction

`2AgCl (s) + H_2 (g) ("1 atm") -> 2Ag (s) + 2H^(+)  (0.1 M) +  2Cl^(-) (0.1 M)`

`triangleG^0 = -43600 J at 25^@ C`

Calculate the e.m.f. of the cell

`[log 10^(-n) = -n]` 

Write two advantages of fuel cell

An analysis shows that FeO has a non-stoichiometric composition with formula Fe_0.95O. Give reason.

Complete and balance the following chemical equations

`Fe^(2+) + MnO_4^(-) + H^+ ->`

Complete and balance the following chemical equations

`MnO_4^(-) + H_2O + I^(-) ->`

Give reasons: E° value for the Mn³⁺/Mn²⁺ couple is much more positive than that for Fe³⁺/Fe²⁺.

Give reasons Iron has the higher enthalpy of atomization than that of copper.

Give reasons: Sc³⁺ is colourless in aqueous solution whereas Ti³⁺ is coloured.

Write the formula for the given coordination compound:

Iron (III) hexacyanoferrate (II)

CO (g) and H₂ (g) react to give different products in the presence of different catalysts. Which ability of the catalyst is shown by these reactions?

Write the coordination number and oxidation state of Platinum in the complex [Pt(en)₂Cl₂].