Class 12th

The standard enthalpies of formation of Al₂O₃ and CaO are –1675 kJ mol⁻¹ and -635 kJ mol⁻¹ respectively.
For the reaction 3CaO + 2Al → 3Ca + Al₂O₃ the standard reaction enthalpy ΔᵣH° = _______ kJ.
(Round off to the nearest integer).

A plane electromagnetic wave of frequency 100 MHz is traveling in vacuum along the x-direction. At a particular point in space and time, B = 2.0 * 10? k? T. (where, k? is unit vector along z-direction) What is E at this point? (speed of light c = 3 x 10? m/s)

15 mL of aqueous solution of Fe²⁺ in acidic medium completely reacted with 20 ml of 0.03 M aqueous Cr₂O₇^2-. The molarity of the Fe²⁺ solution is _______ *10^-2 M (Round off to the nearest integer).

Match List-I with List-II

Choose the most appropriate answer from the options given below :

Four identical long solenoids A, B, C and D are connected to each other as shown in the figure. If the magnetic field at the centre of A is 3T, the field at the centre of C would be: (Assume that the magnetic field is confined within the volume of respective solenoid).

The reaction of white phosphorous on boiling with alkali in inert atmosphere resulted in the formation of product 'A'. The reaction of 1 mol of 'A' with excess of AgNO₃ in aqueous medium gives _______ mol(s) of Ag. (Round off to the nearest integer).

Two cells of emf 2E and E with internal resistance r? and r? respectively are connected in series to an external resistor R (see figure). The value of R, at which the potential difference across the terminals of the first cell becomes zero is:

For a certain first order reaction 32% of the reactant is left after 570s. The rate constant of this reaction is _______ *10⁻³ s⁻¹. (Round off to the nearest integer).
[Given: log₁₀2 = 0.301, ln10 = 2.303]

A carrier signal C(t) = 25 sin(2.512 * 10¹⁰t) is amplitude modulated by a message signal m(t) = 5 sin(1.57 * 10⁸t) and transmitted through an antenna. What will be the bandwidth of the modulated signal?

Your friend is having eye sight problem. She is not able to see clearly a distant uniform window mesh and it appears to her non-uniform and distorted. The doctor diagnosed the problems as: