The half-life of a first-order reaction is 13 min. If the initial concentration of reactant is 0.13 M, it takes min for it to decrease to 0.085 M. A) 12 B) 10. C) 8.0 D) 11 E) 5.0 C

Answer : The correct option is, (C) 8.0 min

Explanation :

Half-life = 13 min

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  = 0.13 M

a - x = amount left after decay process = 0.085 M

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

Therefore, the time taken is, 8.0 min.

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.