List of practice Questions

In the reaction given below, water behaves as \(NH_3 + H_2O \rightleftharpoons NH_4^+ + OH^-\)

White phosphorus reacts with aqueous NaOH to form \(PH_3(g)\) and sodium hypophosphite. When 6.2g of white phosphorus reacted with 500 mL of xM NaOH solution, the concentration of sodium hypophosphite in the resultant solution was \(0.3 \text{ mol L}^{-1}\). What are x (in M) and weight (in g) of \(PH_3\) formed respectively? (\(P=31\) u; \(H=1\) u; \(O=16\) u)

At constant temperature, one mole of an ideal gas of volume 2L expanded to 100 L against an external pressure of 1 atm under reversible conditions. What is the work done (in J)? (1 L atm = 101.3 J; \(\log 5 = 0.7\))

If the energy required to remove an electron from the ground state of \(He^+\) is \(x\) J, the energy (in J) required to remove an electron from the ground state of \(Li^{2+}\) is:

Which of the following is not the correct order of atomic radius of the elements given?

Observe the following reaction: \(Na_2B_4O_7 + H_2O \rightarrow \text{Acid} + \text{Alkali}\). The hybridisation of the central atom of the acid is:

Which of the following sets of molecules / ions represent isoelectronic species?

Given below are two statements:
Statement - I: London forces between two particles are proportional to \(r^{-6}\), where 'r' is the distance between two particles.
Statement - II: The dipole-dipole interaction energy in a solid is proportional to \(r^{-3}\) where r is the distance between two polar molecules.

Two identical photo cathodes receive light of frequencies \( f_1 \) and \( f_2 \). If the velocity of photo electrons (of mass m) coming out are respectively \( V_1 \) & \( V_2 \) then:

Suppose an electron is attracted towards the origin by a force \( K/r \), where K is a constant and r is the distance of the electron from the origin. By applying Bohr model to this system, the radius of the \( n^{th} \) orbit of the electron is found to be \( r_n \), and the kinetic energy of the electron to be \( T_n \), then which of the following is true?

The radioactivity of a certain radioactive element drops to 1/64 of its initial value in 30 sec. Its half-life is:

In the following circuit, the value of Y is:

An audio signal \( 10 \sin 2\pi(1500)t \) volt amplitude modulates a carrier \( 40 \sin 2\pi(10^5)t \) volts. The modulation factor and percentage modulation are:

The threshold frequency of a metal is \(1.15 \times 10^{15}\) Hz. If electrons with kinetic energy of \(0.20\) eV are ejected when this metal surface is irradiated with photons of frequency '\(\nu\)', the value of \(\nu\) is (\(h=6.60 \times 10^{-34}\) Js, \(1\) eV \(=1.6 \times 10^{-19}\) J)

A particle having charge 'q' enters a uniform transverse magnetic field \( \vec{B} \). It is deflected through a distance 'x' while travelling a distance 'y' as shown in figure. The magnitude of the momentum of the particle is:

A current carrying circular coil of radius 'r' produces a magnetic induction of 1 T at its centre. The magnetic induction at a distance of \(\sqrt{3}r\) on its axis from its centre is:

Two identical bar magnets are placed one above the other such that they are mutually perpendicular and bisect each other. The time period of this combination in a horizontal magnetic field is 'T'. The time period of each magnet in the same field is:

A metal sheet is placed in a magnetic field whose magnitude changes from zero to maximum. The direction of eddy currents produced in the plate is shown in the figure. Then the direction of magnetic field is:

In an ac circuit containing Resistance R and capacitance C, the current is I. Keeping the ac voltage constant, if the frequency is made \( \frac{1}{3} \), the current is \( \frac{I}{2} \). Then the ratio of initial reactance to the resistance is:

The electric field intensity produced by the radiations coming from 100W bulbs at 3m distance is E. The electric field intensity produced by the radiations coming from 50W bulbs at the same distance is:

Interference fringes produced by a double slit arrangement using a monochromatic light of wave length 5,890Å have an angular fringe width \( 0.28^\circ \). If the entire arrangement is immersed in water, the new angular fringe width will be (\( ^a\mu_w = 4/3 \)):

Two similar rods of length \( l=1 \text{ m} \) carrying equal charges \( (q) = 10^{-8} \text{ C} \) are placed as shown in figure. The electric field at point 'O' approximately is, if \( d=0.25 \text{ m} \):

The work done to keep three charges \( 2 \times 10^{-5} \text{ C} \), \( 3 \times 10^{-5} \text{ C} \), \( 4 \times 10^{-5} \text{ C} \) at vertices of an equilateral triangle of side 10 cm is:

A capacitor of 10 \(\mu\text{F}\) charged up to 200 V is connected in parallel with another capacitor of 20 \(\mu\text{F}\) charged up to 50 V. The common potential is:

In the circuit shown, the current through 8 ohm is same before and after connecting E. The value of E is: