ECAT Pre Engineering Chemistry Chapter 5 MCQ Test With Answer

Which of the following was discovered first:

• Charge to mass ratio of electrons. A
• Mass of electrons. B
• Charge of electrons. C
• All of above at same time. D

No cathode rays are produced in the discharged tube when gas is under ordinary pressure even if voltage of 5000 to 10000 is applies. This reason is

• Voltage is low A
• Discharge tube is not coloured B
• Gas does not conduct current under ordinary pressure C
• Temperature low D

The rules which describe the distribution of electron in atomic energy levels are Auf-ban principle, Pauli's exclusion principle. Hunds rule. The pauli exclusion principle refers to the

• Orientation of orbital in space A
• Fact that two electrons in the same orbital should have opposite spins B
• Energy of the orbital C
• Spin of the electron D

When 6s orbital is complete then next electron goes to

• 6p A
• 6d B
• 5d C
• 4f D

Quantum number values for 2p orbitals are

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

Schrodinger wave equation describes electron completely because

• It describes a set of four quantum number A
• It describes the particle nature of electron B
• It measures wavelength of electron C
• It describes electron moving in specific orbit D

In Bohr model of hydrogen atom the distance between adjacent orbits increases away from the nucleus, the energy difference between the orbits

• Increases A
• Decreases B
• Reaming same C
• Orbits coincide D

Which of the following particles has longest wavelength, if they have same speed:

• Proton. A
• Neutron. B
• Electron. C
• Positron. D

Subsidiary quantum number specifies

• size of orbital A
• shape of orbital B
• orientations of orbitals C
• Nuclear stability D

When cathode rays strike the anode metal X-rays are emitted and not the positive rays because

• Cathode rays are material particles A
• Cathode rays knock out electrons from anode, which emit X-rays when outer electron take their place B
• Cathode rays are absorbed by the nucleus C
• Cathode rays become heated D

An electron with n = 3 , l = 2 will be in the sub-shell

• 3p A
• 3d B
• 3f C
• 3s D

e/m of cathode rays is same but for positive rays e/m changes by changing gas in the discharge tube because

• Cathode rays are small sized particles A
• Cathode rays have same charge B
• Nature of cathode rays same for all gasses, but masses of nuclei are different for different gases C
• Temperature of cathode rays higher D

• s A
• p B
• d C
• f D

The uncertainty principle was stated only

• De Brogilie A
• Heinsenberg B
• Einstein C
• Schrodinger D

Pauli's principle is applicable to

• Degenerate orbits A
• Two electrons in the same orbital B
• One electron C
• None D

Which of the following is not a sub-atomic particle

• Electron A
• Proton B
• Neutron C
• Deuteron D

Splitting of spectral lines when atoms are subjected to strong electron field is called

• Zeeman effect A
• Stark effect B
• Photoelectric effect C
• Compton effect D

The credit of discovering neutron goes to

• Rutherford A
• Langmuir B
• Chadwick C
• Austen D

The electronic configuration of an atom/ion can be defined by the following

• Aufbau principle A
• Pauli's exclusion principle B
• Hund's Rule C
• All the above D

The total number of orbitals in a shell with principal quantum number 'n' is

• 2n A
• 2n² B
• n² C
• n + 1 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 size of electronic shell is described by

• Azimuthal Q. no A
• Magnetic Q.No B
• Spin Q. No C
• Principle Q. No D

The charge of an electron is determined by

• J.J. Thomson A
• Crooks B
• Perrin C
• R.A.Millikan 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

Neutron was discovered by:

• Chadwick. A
• Bohr. B
• Rutherford. C
• Plank. D

When the 6d orbital is completed the entering electron goes into

• 7f A
• 7 s B
• 7 p C
• 7 d D

The quantum number which describe the orientation of the orbitals is

• Spin quantum number A
• Principle quantum number B
• Azimathal quantum number C
• Magnetic quantum number D

Smallest charge of electricity that has been measured so far is

• Charge on a-rays A
• Charge on electron (1.602 x 10^-19C) B
• Charge on x-rays C
• Charge on gamma rays D

A 4f orbital has

• one node A
• two node B
• three node C
• four nodes D

With increasing principle quantum number, the energy difference between adjacent energy levels in H atom

• Decreases A
• Increases B
• Remains constant C
• Decreases for low value of Z and increase for higher value of Z D