) Iodine-125 emits gamma rays and has a half life of 60 days. If a 20 mg pellet of iodine-125 is implanted into a prostate gland, how much I-125 remains after 1 year

0.3 mg

Explanation:

From

N/No = (1/2)^t/t1/2

N= mass of isotope left after 1 year

No= initial mass of isotope present

t= time elapsed

t1/2 = half life of the isotope

N/20 = (1/2)^365/60

N/20 = (1/2)^6

N= (1/2)^6 × 20

N= 0.3 mg

1. 1 mole of anything contains 6.022x10^23 pieces  

d  

2. a  

3. c, number  

5. 1.24x10^24atoms / 6.022x10^23atoms/mole = 2moles h2 atoms  

6. fe2br3 mass = 2moles x mass fe + 3 moles x mass br  

molar mass = grams / number of moles = g/mole  

to find moles = g / molar mass  

to find mass = g = molar mass / moles

b.final