MCQ on Atoms and Molecules Class 9. We covered all the MCQ on Atoms and Molecules Class 9 in this post for free so that you can practice well for the exam.
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MCQ on Atoms and Molecules for NEET Students
The percentage of mass converted into energy in nuclear fission is about
(A) 10%
(B) 0.01%
(C) 0.1%
(D) 1%
Option c – 0.1%
In alpha decay, the ratio of neutron to proton
(A) increases.
(B) decreases.
(C) remains constant.
(D) may increase or decrease.
Option a – increases.
A sample of the radioactive element has a mass of 20 g at an instant t = 0. What is the approximate mass of this element in the sample after two mean lives?
(A) 5 g
(B) 1.35 g
(C) 2.71 g
(D) 0.8 g
Option c – 2.71 g
The binding energy of the nucleus is the energy
(A) equivalent to that of the mass of the nucleus.
(B) equivalent to that of an atom as a whole.
(C) equivalent to that of packing fraction.
(D) equivalent to that of the mass defect.
Option d – equivalent to that of the mass defect.
A radioactive element X with a half-life period of 2 hours decays giving a stable element Y. If the ratio of X and Y atoms is 1 : 7, then the value of t is
(A) 4 hours
(B) 14 hours
(C) 6 hours
(D) Between 4 and 6 hours
Option c – 6 hours
The half-life of a radioactive substance is 30 minutes. The time taken between 50% decay and 87.5% decay of the substance will be
(A) 15 minutes
(B) 30 minutes
(C) 10 minutes
(D) 60 minutes
Option d – 60 minutes
The number of nuclei undergoing the decay per unit of time is
(A) inversely proportional to the number of unchanged nuclei present at that instant.
(B) directly proportional to the number of unchanged nuclei present at that instant.
(C) equal to the number of unchanged nuclei present at that instant.
(D) zero.
Option b – directly proportional to the number of unchanged nuclei present at that instant.
A certain mass of hydrogen is changed to helium by the process of fusion. The mass defect in the fusion reaction is 0.03866 u. The liberated per u is (given 1 u = 931 MeV) energy
(A) 3.59 MeV
(B) 35 MeV
(C) 9 MeV
(D) 13.35 MeV
Option c – 9 MeV
During negative beta decay,
(A) a neutron in the nucleus decays emitting an electron.
(B) a proton that is already present within the nucleus is ejected.
(C) a part of the binding energy of the nucleus is converted into an electron.
(D) an atomic electron is ejected.
Option a – a neutron in the nucleus decays emitting an electron.
If a radioactive substance has a mean life of 5 hours, then in this time
(A) all active nuclei will decay
(B) less than 50% of the active nuclei will decay
(C) less than 60% of the active nuclei will decay
(D) more than 70% of the active nuclei will decay
Option d – more than 70% of the active nuclei will decay
If a radioactive nucleus emits a beta particle, then the parent and daughter nuclei are ………
(A) isotopes
(B) isotones
(C) isomers
(D) isobars
Option d – isobars
16 g of radioactive radon is kept in a container. How much radon will disintegrate in 18 days? The half-life of radon is 3.6 days.
(A) 0.5 g
(B) 3.6 g
(C) 16 g
(D) 2 g
Option a – 0.5 g
The masses of the proton and neutron are 1.0073 a.m.u. and 1.0087 a.m.u. respectively. The neutrons and protons combine to form a helium nucleus (alpha particles) of mass 4.0015 a.m.u. What is the binding energy of the helium nucleus thus formed? (1 a.m.u. 931 MeV)
(A) 14.2 MeV
(B) 28.4 MeV
(C) 20.8 MeV
(D) 27.3 MeV
Option b – 28.4 MeV
The half-life of a radioactive substance is 26 minutes. The time (in minutes) taken between 40% decay and 85% decay of the same radioactive substance is
(A) 13
(B) 52
(C) 26
(D) 676
Option b – 52
Choose the INCORRECT one :
(A) The energy equivalent to that of mass defect is called the binding energy of the nucleus.
(B) Mass defect per nucleon is called packing fraction.
(C) The energy equivalent to 1 amu is 931 MeV.
(D) The energy and mass are not interconvertible.
After 24 hours, the activity of a radioactive sample is 3000 DPS (disintegrations per second). After another 12 hours, the activity reduces to 1500 DPS. The initial activity of the sample in DPS is
(A) 1000
(B) 9000
(C) 3000
(D) 12000
Option d – 12000
In any fission process, the ratio of the mass of the parent nucleus to the mass of fission products is ……….
(A) greater than I
(B) less than I
(C) depends on the mass of the parent nucleus
(D) equal to I
Option a – greater than I
A radioactive sample with a half-life of 1 month has the label: Activity = 2 microcurie on 1-3-2013. What was its activity before 3 months?
(A) 16 microcurie
(B) 4 microcurie
(C) 1 microcurie
(D) 8 microcurie
Option a – 16 microcurie
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