August 2010 Chemistry Regents #79 to 81

Highlight to reveal answers and explanations

 

Questions 1-10 Questions 11-20 Questions 21-30 Questions 31-40 Questions 41-50

Questions 51-53 Questions 54-56 Questions 57-58 Questions 59-60 Questions 61-63 Questions 64-66 Questions 67-69 Questions 70-72 Questions 73-74 Questions 75-78 Questions 79-81

 

Other Regents Exams

Questions

 

Base your answers to questions 79 through 81 on the information below.

The radioisotope uranium-238 occurs naturally in Earth’s crust. The disintegration of this radioisotope is the first in a series of spontaneous decays.

The sixth decay in this series produces the radioisotope radon-222. The decay of radon-222 produces the radioisotope polonium-218 that has a half life of 3.04 minutes. Eventually, the stable isotope lead-206 is produced by the alpha decay of an unstable nuclide.

 

79 Explain, in terms of electron configuration, why atoms of the radioisotope produced by the sixth decay in the U-238 disintegration series do not readily react to form compounds. [1]

HIGHLIGHT TO SEE THE ANSWER

Radon-222 atoms have a complete outer shell of electrons and tend not to bond.

There are eight valence electrons in a radon atom.

octet in valence shell

80 Complete the nuclear equation in your answer booklet for the decay of the unstable nuclide that produces Pb-206, by writing a notation for the missing nuclide. [1]

HIGHLIGHT TO SEE THE ANSWER

210 Po ==> 4 He + 206 Pb
84 2 82

81 Determine the original mass of a sample of Po-218, if 0.50 milligram of the sample remains unchanged after 12.16 minutes. [1]

HIGHLIGHT TO SEE THE ANSWER

 

Answer=8.00 mg

12.16min/3.04min = 4 half lives

0.50mg==>1.0==>2.0==>4.0==>8.0mg

Back to Regents Exams

Questions 1-10 Questions 11-20 Questions 21-30 Questions 31-40 Questions 41-50

Questions 51-53 Questions 54-56 Questions 57-58 Questions 59-60 Questions 61-63 Questions 64-66 Questions 67-69 Questions 70-72 Questions 73-74 Questions 75-78 Questions 79-81

 
Back to Regents Exams