SOLVED

31) What is the decay constant for 131I if the half-life is 8.04 d? A) 9.98 x 10-7 s-1 B) 9.31 x 10-5 s-1 C) 3.48 x 10-6 s-1 D) 4.81 x 10-4 s-1 32) A nuclide has a decay constant of 4.28 × 10-4/h. If the activity of a sample is 3.14 × 105/s, how many atoms of the nuclide are present in the sample? A) 7.34 × 108 B) 2.64 × 1012 C) 4.84 × 105 D) 1.34 × 102 E) 2.34 × 1011 33) The charcoal from ashes found in a cave gave 3.34 14C counts per gram per minute. Wood from the outer portion of a growing tree gives a comparable count of 16.0. The half-life of 14C is 5700 years. How old are the ashes? A) 8.93 × 103 yr B) 6.87 × 103 yr C) 1.29 × 104 yr D) 1.93 × 104 yr E) 1.90 × 104 yr 34) A wooden artifact is subjected to radiocarbon dating. The activity associated with its 14C content is 12 dis min-1 g-1. A sample of wood from a modern source gave 15 dis min-1 g-1. If the half-life of 14C is 5730 y, what is the age of the artifact? A) 1.8 x 103 y B) 800 y C) 1.3 x 103 y D) 7.2 x 103 y 35) If the decay constant for 131I is 9.98 x 10-7 s-1, calculate the activity of a 1.00 mg sample. A) 4.59 x 1012 atoms/s B) 4.73 x 1012 atoms/s C) 4.61 x 1024 atoms/s D) 9.98 x 10-4 atoms/s 36) Half-life is: I) the time for a sample to decay completely. II) constant for a given radioisotope. III) the time required for half of a sample to decay. IV) inversely proportional to the decay constant. A) I and II B) I, II, and III C) I and III D) I, III, and IV E) II, III, and IV 37) The observation that a 30 g sample of C-14 has a decay rate faster than that of a 20 g sample of C-14 would be consistent with the: A) Half-Life Principle B) Disintegration Rule C) Radioactive decay law D) Mass-Rate Principle E) Mass-decay ratio 38) The half-life of 238U, which decomposes to 206Pb, is 4.51 × 109 y. A rock contains equal masses of these two isotopes. How old is this rock? A) 4.07 × 109 y B) 4.06 × 109 y C) 9.02 × 109 y D) 4.51 × 109 y E) 5.00 × 109 y 39) The following nuclear reaction is known to occur: 2 → This reaction is used in a fusion bomb or H bomb. How many joules of energy are produced by this reaction if 33.0 g of 2H are used? You are given the following masses: electron 0.00055 amu; proton 1.00782 amu; neutron 1.00867 amu; 2H atom 2.010410 amu; atom 4.00260 amu. A) 3.82 × 10-12 J B) 2.30 × 1012 J C) 3.77 × 1013 J D) 7.60 × 1013 J E) 1.34 J 40) The masses of , and are 4.0015, 6.0135 and 10.0102 amu, respectively. Splitting a boron-10 nucleus to helium-4 and lithium-6 would: A) absorb energy B) evolve energy C) result in no energy change D) cannot be determined E) boron cannot be split