Half-life problems:
(a) hg-197 has a half-life of 64 hours. if you have 164g of hg-197 today, how much will you have in 448 hours?

(b) 263 minutes ago we had 5.12g of i-134 and now we only have 0.16g. how long is the half-life of i-134?

(c) c-14 has a half-life of 5730 years. if animal remains are found to have 1/16 of the amount of c-14 found in animals living today, how old are the remains?

(d) an average smoke detector for domestic use contains about 0.29 micrograms of
am-241 which has a half-life of 432 years. how long would it take to decay to 0.0725 micrograms? (3 pts)

A) answer 1.281 grams

B) 52.60 days

C) 23250 years  

D)  864 years  

Explanation:

A) Solution

Ending Amount = Beginning Amount / 2(time / half-life)

Ending Amount = 164 / 2(⁴⁴⁸/⁶⁴)

Ending Amount = 164 / 2⁷

Ending Amount = 164 / 128

Ending Amount = 1.281 grams

B) solution

Half life = (time * log 2) / log (beginning amount / ending amount)

Half life = (263 * .30103) / log (5.12 / 0.16)

Half life = 79.17 / log (32)

Half life = 79.17 / 1.505

Half life =  52.60 days

C) Solution

As we have half-life =5730  

1/16 =  6.2 percent  

Remains =    23250 years  

D) solution

elapsed time = half life * log (beginning amount / ending amount) / log 2

elapsed time = 432 * (log (0.29 / 0.0725) / .30103)

elapsed time = 432 * (0.602 / .30103)

elapsed time=  432 (2)

= 864 years  

both adhesion and cohesion are attractions.

they are different in that adhesion is the force of attraction between the molecules of two different substances, whereas cohesion is the force of attraction between molecules of the same substance.

possible examples include capillary action, in which the adhesion between water and glass causes the water to rise in a narrow tube against the force of gravity.

because of hydrogen bonding, water is extremely cohesive.

this causes molecules on the surface of water to be drawn inward, which is why drops of water form beads on smooth surfaces.

hope this .