List of practice Questions

Boron trifluoride on reaction with lithium aluminium hydride in ether gives LiF, AlF\(_3\) and X. X on reaction with NH\(_3\) gives Y. Y on further heating gives a compound Z. The number of \(\sigma\)-bonds and \(\pi\)-bonds in Z are x and y respectively. (x+y) is equal to
In long form of periodic table an element 'E' has atomic number 78. The period and group number of the element are x and y respectively. (x+y) is equal to
In which of the following options, the molecules are correctly arranged in the increasing order of their bond angles?
In which of the following, the compounds are correctly arranged in the decreasing order of boiling points?
The force (F) required to maintain the flow of layers of a liquid is equal to (A = area of contact of layers, dz = distance between the layers, du = change in velocity, \(\eta\) = coefficient of viscosity)
Consider the following redox reaction in basic medium. \( x\text{Cr(OH)}_3 + y(\text{IO}_3)^- + z(\text{OH})^- \rightarrow a(\text{CrO}_4)^{2-} + b(\text{I})^- + c(\text{H}_2\text{O}) \). The incorrect option about it is
At absolute zero temperature, a semiconductor behaves like
Three logic gates are connected as shown in the figure. If the inputs are A=1, B=0 and C=1, then the values of \(y_1, y_2\) and \(y_3\) respectively are
The radio horizon of a transmitting antenna of height 39.2 m is (Radius of the earth = 6400 km)
The radius of second orbit of hydrogen atom is same as that of orbit (n) of an ion (x). n and x are respectively
An electromagnetic radiation of wavelength 331.5 nm is made to strike the surface of a metal. Electrons are emitted with a kinetic energy of \(1.2 \times 10^5\) J mol\(^{-1}\). The work function (in eV) of the metal is (h=\(6.63 \times 10^{-34}\) Js, \(N_A = 6 \times 10^{23}\) mol\(^{-1}\))
The inductance L, Capacitance C and resistance R are the values of the components connected in series to an ac source of angular frequency \(\omega\). The inductive and capacitive reactances are \(X_L\) and \(X_C\) respectively. If the circuit is purely resistive, then
If the rate of change of electric field across the plates of a parallel plate capacitor is E and the displacement current is I, then the area of one plate of the capacitor is (\(\epsilon_0\) is permittivity of free space)
The work done to accelerate an electron from rest so that it can have a de Broglie wavelength of 6600 Å is nearly (Planck's constant = \(6.6 \times 10^{-34}\) Js and mass of electron = \(9 \times 10^{-31}\)kg)
If the total energy of an electron in an orbit is positive, then
If 87.5% of atoms of a radioactive element decay in 6 days, then the fraction of atoms of the element that decay in 8 days is
If the ratio of the mass numbers of two nuclei is 27:125, then the ratio of their surface areas is
The lengths of two wires made of the same material are in the ratio 2:3 and their radii are in the ratio 1:2. If the two wires are connected in parallel to a battery, then the ratio of the drift velocities of free electrons in the two wires is
In a potentiometer experiment for the determination of the internal resistance of a cell, when an external resistance of R is connected parallel to the cell, the balancing length decreases by 10%. The internal resistance of the cell is
The number of turns of two circular coils A and B are 300 and 200 respectively. The magnetic moments of the two coils A and B are in the ratio 1:2. If the two coils carry equal currents, then the ratio of radii of coils A and B is
Two long straight parallel wires carry currents of 8 A and 10 A in opposite directions. If the distance of separation between the wires is 9 cm, then the net magnetic field at a point between the two wires, which is at a perpendicular distance of 4 cm from the wire carrying 8 A current is
A short bar magnet of magnetic moment 2.5 Am\(^2\) is kept in a uniform magnetic field of \(4 \times 10^{-5}\) T. The work done in moving the magnet from its most stable position to most unstable position is
The radius of a coil of N turns is R. If the plane of the coil is placed parallel to a uniform magnetic field B, then the flux linked with the coil is
A metal rod of length 125 cm is clamped at its midpoint. If the speed of the sound in the metal is 5000ms\(^{-1}\), then the fundamental frequency of the longitudinal vibrations of the rod is
If the distances of the object and its real image from the principal focus of a concave mirror are 16 cm and 9 cm respectively, then the focal length of the mirror is