Carbon-14 is a radioactive isotope that decays according to first-order kinetics in a process that has a half-life of 5730 years. if a sample containing carbon-14 now has 71% of its original concentration of carbon-14, how much time has passed in years? 4.09 ~ 103 years 5.73 x 103 years 2.38 x 103 years 2.83 x 103 years 3.52 * 104 years

Answer : The time passed in years is

Explanation :

Half-life = 5730 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 = let initial amount of the reactant  = X g

a - x = amount left after decay process =

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

Therefore, the time passed in years is

when the volume of gas is   changed from   717.73 ml   to 852 ml   the temperature will   change   from 315   c to 452   c

    calculation

this is calculated using the charles law formula

that is,   v1/t1 = v2/t2

          v1=?

        t1 = 315 c   into   kelvin = 315 +273 = 588 k

        v2 = 852   ml

        t2 = 425c + 273 =698 k

make v1   the subject of the formula ( by   multiplying both side by t1)

  v1=( v2 xt1) / t2

v1= (852 ml   x 588 k)/ 698 k= 717.73 ml

the correct answer is:

a. formation of precipitation