Answer Happy

13 of 15 A radioisotope tracer has a half-life of 30 seconds. If a level of <1% is considered safe, when would the soonest a sample injected with the tracer be safe to handle? about 100 seconds about 99 seconds about 200 seconds about 30 seconds 14 of 15 A reaction mechanism consisting of three steps, two fast and one slow, cannot be dependent on the slow step second order first order zero order 15 of 15 A student says that due to the concept of half-lives, a chemical will never completely disappear and only approach zero since taking half of each succeeding number is always greater than zero. Which explanation corrects the student's thinking? The student is right- matter is neither created nor destroyed. When you take a half of a half of a half, eventually it does become zero. The concept is statistical- it will get too small to detect eventually. Sometimes more than half the chemicals react, so it really does go to zero.