The isotope radium-226 decays into radon-222, with a half-life of around 1,600 years. if a rock contained 6 grams of radium-226 when it reached its closure temperature but only 0.375 grams when it was discovered, which two statements about the rock are true? a] the rock reached its closure temperature 6,400 years ago. b] the rock reached its closure temperature 4,800 years ago. c]the rock had 2.625 grams of radon-222 1,600 years ago. d]when the rock was discovered, it had 5.625 grams of radon-222. e]when the rock was discovered, it had 3.375 grams of radon-222.

Answer : The correct option is, (A) The rock reached its closure temperature 6,400 years ago.

Explanation :

Half-life = 1600 years

First we have to calculate the rate constant, we use the formula :

Now we have to calculate the time passed.

Expression for rate law for first order kinetics is given by:

where,

k = rate constant  =

t = time passed by the sample  = ?

a = initial amount of the reactant  = 6 g

a - x = amount left after decay process = 0.375 g

Now put all the given values in above equation, we get

Therefore, the correct option is, (A) The rock reached its closure temperature 6,400 years ago.

the answer is

c. parental