Full Question: Technetium-99m is an ideal radioisotope for scanning organs because it has a half-life of 6.0 h and is a pure gamma emitter. Suppose that 84.1 mg were prepared in the technetium generator this morning. How many milligrams of technetium-99 m would remain after the following intervals?
Options:
- One half life
- Two half lives
- 18h
- 24h
Answer:
a) 42.05mg
b) 21.025mg
c) 10.5125mg
d) 5.25625mg
Explanation:
Half life = 6h
Initial Amount = 84.1mg
Before proceeding further;
The half life a material is simply the amount of time it takes for half of that material to decay.
a) One half life
84.1mg --> 84.1mg / 2 = 42.05mg (First Half life)
b) Two half lives
84.1mg --> 84.1mg / 2 = 42.05mg (First Half life)
42.05mg --> 42.05mg / 2 = 21.025mg (Second Half life)
c) 18h
This is the same as three half lives because; 3 * 6 = 18
84.1mg --> 84.1mg / 2 = 42.05mg (First Half life)
42.05mg --> 42.05mg / 2 = 21.025mg (Second Half life)
21.025mg --> 21.025mg / 2 = 10.5125mg (Third Half life)
d) 24h
This is the same as four half lives because; 4 * 6 = 24
84.1mg --> 84.1mg / 2 = 42.05mg (First Half life)
42.05mg --> 42.05mg / 2 = 21.025mg (Second Half life)
21.025mg --> 21.025mg / 2 = 10.5125mg (Third Half life)
10.5125mg --> 10.5125mg / 2 = 5.25625mg (Fourth Half life)
