Friedel-Crafts acylation is-
(A) α-acylation of a carbonyl compound (B) acylation of phenols to generate esters
(C) acylation of aliphatic olefins (D) acylation of aromatic nucleus
A piece of hot copper at 100ºC is plunged into a pond at 30ºC. The copper cools down to 30ºC, while the
pond, being huge, stays at its initial temperature. Then-
(A) copper loses some entropy, the pond stays at the same entropy
(B) copper loses some entropy, and the pond gains exactly the same amount of entropy
(C) copper loses entropy, and the pond gains more than this amount of entropy
(D) both copper and the pond gain in entropy
A charged particle of charge q and mass m, gets deflected through an angle θ upon passing through a square
region of side 'a' which contains a uniform magnetic field B normal to its plane. Assuming that the particle
entered the square at right angles to one side, what is the speed of the particle ?
Two masses m1 and m2 are connected by a massless spring of spring constant k and unstreched length l. The
masses are placed on a frictionless straight channel – which we consider our x-axis. They are initially at rest
at x = 0 and x = l, respectively. At t = 0, a velocity of v0 is suddenly imparted to the first particle. At a later
time t0, the centre of mass of the two masses is
A book is resting on shelf that is undergoing vertical simple harmonic oscillations with an amplitude of
2.5 cm. What is the minimum frequency of oscillation of the shell for which the book will lose contact with
the shelf ? (Assume that g = 10 m/s2)
(A) 20 Hz (B) 3.18 Hz (C) 125.6 Hz (D) 10 Hz
A nucleus has a half-life of 30 minutes. At 3 PM its decay rate was measured as 120,000 counts/sec. What
will be the decay rate at 5 PM ?
(A) 120,000 counts/sec (B) 60,000 counts/sec
(C) 30,000 counts/sec (D) 7,500 counts/sec
A point source of light is placed at the bottom of a vessel which is filled with water of refractive index μ to a
height h. If a floating opaque disc has to be placed exactly above it so that the source is invisible from above,
the radius of the disc should be-
Pure mathematics is the world's best game. It is more absorbing than chess, more of a gamble than poker, and lasts longer than Monopoly. It's free. It can be played anywhere - Archimedes did it in a bathtub.