chemistry : class12 Polonium in Uranium Ores : Occurrence of Group 16 elements : p-Block Elements MCQ Questions and Answers
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Polonium in Uranium Ores
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MCQ Questions
1. Polonium was originally isolated from which uranium-bearing mineral obtained from uranium ores?
A.
Bauxite
B.
Pitchblende
C.
Chalcopyrite
D.
Dolomite
Correct Answer:
Pitchblende
Explanation:
Polonium was discovered in pitchblende, a uranium-rich ore. It occurs there only in extremely small quantities as a radioactive product of uranium decay.
2. The occurrence of polonium in uranium ores is best explained by its formation as a:
A.
Stable oxidation product of uranium
B.
Radioactive daughter product in a uranium decay series
C.
Sulphide impurity formed by bacterial action
D.
Volatile compound produced during ore roasting
Correct Answer:
Radioactive daughter product in a uranium decay series
Explanation:
Polonium isotopes found in uranium ores arise through radioactive transformations in uranium decay chains rather than through ordinary chemical oxidation or mineral formation.
3. Why is polonium present only in trace quantities in uranium ores despite being associated with uranium minerals?
A.
It is rapidly consumed in radioactive decay and is continuously regenerated in minute amounts
B.
It is chemically converted completely into uranium during crystallization
C.
It is absent from the decay products of uranium
D.
It dissolves only in atmospheric moisture after the ore forms
Correct Answer:
It is rapidly consumed in radioactive decay and is continuously regenerated in minute amounts
Explanation:
Polonium is radioactive and has relatively short-lived isotopes compared with uranium. Consequently, it is continually formed in the decay chain but also decays rapidly, so only trace amounts accumulate in uranium ores.
4. Which statement most accurately describes the relationship between polonium and uranium in uranium ores?
A.
Polonium is the principal stable isotope of uranium
B.
Polonium is a radioactive decay product associated with uranium-bearing minerals
C.
Polonium replaces uranium as the major metallic constituent of the ore
D.
Polonium is produced by the reduction of uranium oxide during mining
Correct Answer:
Polonium is a radioactive decay product associated with uranium-bearing minerals
Explanation:
Polonium occurs in uranium ores because uranium decay chains generate polonium isotopes. It is not the major constituent of the ore and is not produced by a simple chemical reduction of uranium oxide.
5. Which sequence correctly represents the relevant part of the uranium-238 decay chain leading from radium to polonium in uranium ores?
Explanation:
Radium-226 undergoes alpha decay to radon-222, which subsequently undergoes alpha decay to polonium-218. This sequence accounts for polonium occurring among the radioactive products associated with uranium ores.
6. The historical discovery of polonium from uranium ore was significant because it demonstrated that the ore contained:
A.
Only chemically stable uranium compounds
B.
Previously unknown radioactive material distinct from uranium
C.
A large concentration of nonradioactive group 16 elements
D.
A naturally occurring alloy of uranium and lead
Correct Answer:
Previously unknown radioactive material distinct from uranium
Explanation:
Polonium was identified as a new radioactive element separated from uranium ore. Its discovery showed that uranium minerals contain radioactive substances other than uranium itself.
7. Which property most complicates the quantitative recovery of polonium from uranium ores?
A.
Its occurrence in very small amounts together with intense radioactivity
B.
Its complete insolubility in every chemical reagent
C.
Its existence only as a stable gaseous element
D.
Its conversion into uranium immediately upon contact with water
Correct Answer:
Its occurrence in very small amounts together with intense radioactivity
Explanation:
Polonium occurs only in trace quantities in uranium ores and is highly radioactive. These features make its separation and handling difficult compared with the recovery of the major ore constituents.
8. Polonium in uranium ores is most appropriately classified as which type of constituent?
A.
A major gangue mineral
B.
A stable isotope mixture forming the ore matrix
C.
A trace radioactive daughter element
D.
A reagent added during ore purification
Correct Answer:
A trace radioactive daughter element
Explanation:
Polonium is present naturally in uranium ores in trace amounts and is generated through radioactive decay of uranium-series nuclides, so it is a trace radioactive daughter element.
9. The name polonium was chosen by its discoverers primarily to commemorate:
A.
The uranium mines of Belgium
B.
The element's occurrence in polar minerals
C.
Poland, the homeland of Marie Curie
D.
The Polish name for uranium ore
Correct Answer:
Poland, the homeland of Marie Curie
Explanation:
Polonium was named after Poland, the homeland of Marie Curie, who co-discovered the element while investigating radioactive materials in uranium ores.
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