Tag: chemistry

Questions Related to chemistry

Which of the following can be diagnosed by Iodine-131 radioisotope?

chemistry nuclear physics types of radioactivity nuclear chemistry and radioactivity radioactivity

  1. Kidneys

  2. Heart

  3. Lungs

  4. Thyroid

  5. Bone marrow

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Correct Option: D
Explanation:

Iodine in food is absorbed by the body and preferentially concentrated in the thyroid where it is needed for the functioning of that gland. Thus the health problem related to thyroid can be diagnosed by Iodine−131 radioisotope. 

The electromagnetic radiation observed in Radioactivity is ..............

chemistry nuclear physics types of radioactivity nuclear chemistry and radioactivity radioactivity

  1. $\alpha$ - particle

  2. $\beta$ - particle

  3. $\gamma$ - rays

  4. X - rays

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Correct Option: C
Explanation:

Gamma ray (also called gamma radiation) is penetrating electromagnetic radiation of a kind arising from the radioactive decay of atomic nuclei. It consists of photons in the highest observed range of photon energy.

Alpha particles have________kinetic energy and momentum with them. Fill in the blank. 

chemistry nuclear physics types of radioactivity nuclear chemistry and radioactivity radioactivity

  1. less

  2. large

  3. no

  4. all of the above

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Correct Option: B
Explanation:

Alpha particles have large kinetic energy and momentum with them. They are used to bombard the atomic nuclei to convert one element into another (for transmutation)

Nearly all isotopes of elements having mass number _______ are radioactive. 
chemistry nuclear physics types of radioactivity nuclear chemistry and radioactivity radioactivity

  1. Lower than 82

  2. Higher than 82

  3. Higher than 69

  4. Lower than 69

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Correct Option: B
Explanation:

The isotopes of nearly all the elements of atomic number higher than 82 (i.e. lead) are radioactive. There are called the natural radioactive substances.

Which of the following is a radioactive substance?

chemistry nuclear physics types of radioactivity nuclear chemistry and radioactivity radioactivity

  1. Uranium

  2. Radium

  3. Thorium

  4. All of the above 

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Correct Option: D
Explanation:

Substances which disintegrate (or decay) by the spontaneous emission of radiations are called the radioactive substances. Eq. Uranium, radium, polonium, thorium, actinium etc.

Which of the following statements are true?

chemistry nuclear physics types of radioactivity nuclear chemistry and radioactivity radioactivity

  1. The nucleus of an atom becomes radioactive when A - Z is more than Z

  2. Isotopes having radioactive properties are called radio isotopes

  3. Radio isotopes can be prepared artifically by nuclear transmutation

  4. All of the above

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Correct Option: D
Explanation:

The atoms having radioactive properties are called radio isotopes. The nucleus of an atom becomes radioactive when the number of neutrons in the nucleus exceeds the number of protons inside it. $ _{6}C^{14},  _{27}Co^{60},  _{6}C^{12},  _{19}K^{40}$ etc are all examples of naturally occurring radio isotopes. However, they can also be prepared artificially by nuclear transmutation.

The age of fossils can be estimated with the help of which radioisotope?

chemistry nuclear physics types of radioactivity nuclear chemistry and radioactivity radioactivity

  1. $ _{6}C^{14}$

  2. $ _{27}Co^{60}$

  3. $ _{6}C^{12}$

  4. $ _{19}K^{40}$

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Correct Option: A
Explanation:

The age of fossils can be estimated by the study of decay of radioactive carbon atom $ _{6}C^{14}$ in the remains of the dead and decaying material. This process is called carbon dating.

Rate of decay of radioactive substance is altered by :

chemistry nuclear physics types of radioactivity nuclear chemistry and radioactivity radioactivity

  1. pressure

  2. temperature

  3. chemical change

  4. none of the above 

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Correct Option: D
Explanation:

Any physical changes (temperature, pressure and temperatures) or chemical changes do not alter the rate of decay of the radioactive substances.

Which of the following is used by an archaeologist to determine the age of an artifact, in percentage?

chemistry nuclear physics types of radioactivity nuclear chemistry and radioactivity radioactivity

  1. $Carbon-14$

  2. $Phosphorus-31$

  3. $Hydrogen-3$

  4. $Chlorine-37$

  5. $Bromine-81$

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Correct Option: A
Explanation:

Carbon−14 is used by an archaeologist to determine the age of an artifact, in percentage.
The ratio C-14 / C-12 in fresh sample is compared with the ratio in dead sample.

The radioactivity of a sample is $R _ { 1 } $at a time $T _ { 1 }$ and $R _ 2$ at a time $ T _ 2 $ . If the half-life of the specimen is T  ,  the number of atoms that have disintegrated in the time $T _ 2 - T _  1 $ is proportional to 

chemistry nuclear physics types of radioactivity nuclear chemistry and radioactivity radioactivity

  1. $T _2-T _1\alpha(R _1-R _2)T$

  2. $\left( R _ { 1 } - R _ { 2 } \right)$

  3. $\left( R _ { 1 } - R _ { 2 } \right) / T$

  4. $\left( R _ { 1 } - R _ { 2 } \right) T$

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Correct Option: A
Explanation:
[D]
$\begin{array}{l} { R _{ 1 } }=\lambda { N _{ 1 } } \\ { R _{ 2 } }=\lambda { N _{ 2 } } \end{array}$
Number of atoms disintegrated in time 
$\begin{array}{l} { T _{ 2 } }-{ T _{ 1 } }={ N _{ 1 } }-{ N _{ 2 } }=\dfrac { { { R _{ 1 } }-{ R _{ 2 } } } }{ \lambda  }  \\ \lambda =\dfrac { { 0.693 } }{ T }  \\ { T _{ 2 } }-{ T _{ 1 } }=\dfrac { { { R _{ 1 } }-{ R _{ 2 } }\times T } }{ { 0.693 } }  \\ { T _{ 2 } }-{ T _{ 1 } }\alpha \left( { { R _{ 1 } }-{ R _{ 2 } } } \right) T \end{array}$