ECAT Pre Engineering Chemistry Chapter 5 MCQ Test With Answer

The valence orbital configuration of an element with atomic number 23 is

• 3d⁵ A
• 3d³, 4s² B
• 3d³, 4s¹, 4p¹ C
• 3d²,4s²,4p¹ D

The third line of the Balmer series, in the emission spectrum of the hydrogen atom,is due to the transition from the

• Fourth Bohr orbit to the first Bohr orbit A
• Fifth Bohr orbit to the second Bohr orbit B
• Sixth Bohr orbit to the third Bohr orbit C
• Seventh Bohr orbit to the third Bohr orbit D

Spectrum of white light is continuous becuase

• Colors separated by dark spaces A
• There are no boundary lines between the colours B
• The radiations are in infrared region C
• The radiatins fall in ultraviolet region D

The symbol of the element whose atoms have the outer most electronic configuration 2s²2p³is

• N A
• Li B
• P C
• Na D

• Plank's equations A
• de Broglie's equations B
• Heisenburg's equation C
• None D

If the value of azimuthal quantum number is 3, then values of m the magnetic quantum no. will be

• 0, 1, 2, 3 A
• +3, +2, +1, -1, -2, -3 B
• 0, -1, -2 ,-3 C
• -3, 0, +3 D

The value of charge on electron is

• 1.602 x 10^-19coulombs A
• 1.602 x 10^-18coulombs B
• 1.602 x 10^-17coulombs C
• 1.602 x 10^-16 coulombs D

The nature of the positive rays depend on

• The nature of the electrode A
• The nature of the discharge tube B
• The nature of the residual gas C
• All of the above D

Anode is the surface on which probability of finding electron is:

• 50% A
• Less than 10%. B
• More than 95%. C
• Zero. D

Which of the following orbitals have a dumb bell shape?

• s A
• p B
• d C
• f D

Electrons in degenerate orbitals are placed in separate orbitals with same spin according to

• Hund's rule A
• Pauli exclusion principle B
• Aufbau principle C
• Mosley's law D

When potassium metal is exposed to violet light

• Ejection of electrons takes place A
• Ejection of some potassium atoms occurs B
• There is no effect C
• The absorption of electrons takes place D

Electrons arranged in orbitals according to the increasing order of their n + l values, this rule is named as

• Hund's rule A
• Heisenberg's principle B
• Paulit exclusion principle C
• Auf bau principle D

If the radius of first Bohr orbit be a_o, then the radius of third Bohr orbit would be

• 3 x a_o A
• 6 x a_o B
• 9 x a_o C
• 1/2 x a_o D

In the ground state of an atom, the electron is present

• In the nucleus A
• In the second shell B
• Nearest to the nucleus C
• Farthest from the nucleus D

The number of electrons in the M shell of the element with atomic number 24 is

• 24 A
• 12 B
• 13 C
• 8 D

Maximum potential energy that an electron can have within the atom is:

• Equal to zero. A
• Less than zero. B
• Greater than zero. C
• Infinite D

With the reference of w/m ratio of anode rays, the e/m ratio of cathode rays s:

• Greater. A
• same. B
• Smaller. C
• Not fixed. D

Rutherford's model of atom failed because:

• The atom did o have a nucleus and electrons A
• It did not account fro the attraction b/w protons and neutrons B
• It did no account for the stability of the atom. C
• There is actually no space b/w the nucleus ad the electrons. D

The radius of first orbit of hydrogen atom

• 0.329 A° A
• 0.429 A° B
• 0.529 A° C
• 0.229 A° D

Energy of electron in an orbit according to Bohr theory is negative due to

• Repulsion of electrons in the same orb A
• At infinity energy is zero ad a traction towards nucleus decreases energy B
• Electron has negative charge C
• Product of positive nuclear charge and negative charge is negative D

Quantum number value for 2p orbitals are:

• n=2 ,l=1 A
• n=1 ,l=2 B
• n= ,l=0 C
• n=2 ,l=0 D

For which of the following sets of quantum numbers and electron will have the highest energy?

• 3,2,1,1/2 A
• 4,2,-1,1/2 B
• 4,1,0,-1/2 C
• 5,0,0,1/2 D

Bohr model of atom is contradicted by:

• Planck's quantum theory A
• Pauli's exclusion theory B
• Heisenberg's uncertainty principle. C
• All of above. D

The divisibility of atom was shown by

• Stoney A
• J.J. Thomson B
• Millikan C
• Rutherford D

Which of the following is not a property of cathode rays

• They can produce x-rays when they strike a heavy metal anode A
• They can cause reduction reaction B
• They produce fluorescence in rare earth and minerals C
• They comprise neutral particles D

In Millikan method the oil droplet falls under the force of gravity but it moves upward due to

• Electric field A
• Magnetic field B
• Incident light C
• X-rays D

Rutherford's atomic model suggests the existence of

• Atom A
• Nucleus B
• alpha particle C
• Measons D

Find the magnetic moment of a divalent ion in aqueous solution if its atomic number is 25

• 3.0 BM A
• 4.9 BM B
• 5.9 BM C
• 6.9 BM D

Which quantum number is sufficient to describe the electron is hydrogen atom?

• l A
• n B
• m C
• s D