Page 512 - Chemistry eBook

piston, this reaction reaches equilibrium, as represented by the equation below.
2SO2(g) + O2(g) 􏰀 2SO3(g) + 392 kJ
79 Explain, in terms of collision theory, why increasing the pressure of the gases in the cylinder increases the rate of the forward reaction. [1]
80 Determine the amount of heat released by the production of 1.0 mole of SO3(g). [1]
81 State, in terms of the concentration of SO (g), what occurs when more O (g) is added
Sample Regents Questions
Base your answers to questions 82 through 85 on the information below.
to the reaction at equilibrium. [1]
32
Nuclear radiation is harmful to living cells, particularly to fast-growing cells, such as
cancer cells and blood cells. An external beam of the radiation emitted from a radioisotope
can be directed on a small area of a person to destroy cancer cells within the body.
Cobalt-60 is an artificially produced radioisotope that emits gamma rays and beta particles. One hospital keeps a 100.0-gram sample of cobalt-60 in an appropriate, secure storage container for future cancer treatment.
82 State one risk to human tissue associated with the use of radioisotopes to treat cancer. [1] 83
83 Compare the penetrating power of the two emissions from the Co-60. [1]
84 Complete the nuclear equation in your answer booklet for the beta decay of the Co-60
by writing an isotopic notation for the missing product. [1] 84 60Co → 0β + ________
27 –1
85 Determine the total time that will have elapsed when 12.5 grams of the original Co-60 sample at the hospital remains unchanged. [1] 85
Jan 2012 #82-85
82
For Raters Only
82
83
84 85
Total Score for Part C
____
y
P.S./Chem.–Jan. ’12 [13] Answer
82) Answer: It can harm living cells
83) Answer: The gamma rays have a stronger penetrating power than the beta particles.
84) Answer: Ni
Explanation: The mass and charge must be balanced on both sides. So X will equal X. To find the element, check Reffy, Periodic Table (p. 9) to find which element has an atomic number of 28. Ni has an atomic number of 28.
85) Answer: 15.8 years
Let’s figure out how many half-lives elapsed for Co-60 to change from 100 grams to 12.5 grams.
It took 3 half-lives to change from 100 grams to 12.5 grams. Reffy, Table N (p. 6) shows that one half-life of
Co-60 is 5.271 years.
3 half-lives = 5.271 x 3 = 15.813 years.
[7]
1 half-life
2 half-lives
3 half-lives
100 = 50 2
50 = 25 2
25 =12.5 2
511 © UNIT 12: NUCLEAR CHEMISTRY