tailieunhanh - SCIENCE REASONING TEST (35 Minutes - 40 Questions)

DIRECTIONS: Each of the following seven passages is followed by several questions. After reading each passage, decide on the best answer to each question and fill in the corresponding oval on your answer sheet. You are allowed to refer to the passages while answering the questions. | 4 if it it it it it it it 4 SCIENCE REASONING TEST 35 Minutes 40 Questions DIRECTIONS Each of the following seven passages is followed by several questions. After reading each passage decide on the best answer to each question and fill in the corresponding oval on your answer sheet. You are allowed to refer to the passages while answering the questions. Passage I Medical researchers and technicians can track the characteristic radiation patterns emitted by certain inherently unstable isotopes as they spontaneously decay into other elements. The half-life of a radioactive isotope is the amount of time necessary for one-half of the initial amount of its nuclei to decay. The decay curves of isotopes 39Y90 and 39Y91 are graphed below as functions of the ratio of N the number of nuclei remaining after a given period to N0 the initial number 1. The half-life of 39Y90 is approximately A. days. B. days. C. 27 days. D. 58 days. 2. What will the approximate ratio of 39Y90 to 39Y91 be after days if the initial samples of the two isotopes contain equal numbers of nuclei F. 1 1 G. 1 2 H. 2 1 J. 10 1 3. When inhaled by humans 39Y90 accumulates in the gastrointestinal tract whereas 39Y91 accumulates in the bones. If the total amount of each isotope inhaled goes to the specified area which of the following situations will exist three days after a patient inhales these substances assuming none of the isotopes leave the specified areas due to physiological factors A. The amount of 39Y91 in the gastrointestinal tract will be approximately equal to the total amount inhaled. B. The amount of 39Y90 in the bones will be approximately one-half of the total amount inhaled. C. The amount of 39Y90 in the gastrointestinal tract will be approximately one-half of the total amount inhaled. D. None of the 39Y91 inhaled will be left in the bones. 264 GO ON TO THE NEXT PAGE. 4 if it it it it it it it 4 4. Approximately how many 39Y91 nuclei will exist after three half-lives have passed