For a first-order reaction, the half-life is constant. it depends only on the rate constant and not on the reactant concentration. it is expressed as: t1/2=0.693/k

for a second-order reaction, the half-life depends on the rate constant and the concentration of the reactant and so is expressed as: t1/2= 1/k[a]0
a. a certain first-order reaction (a--> products) has a rate constant of 3.30×10^-3 s^-1 at 45 degrees c. how many minutes does it take for the concentration of the reactant, [a], to drop to 6.25% of the original concentration?
b. a certain second-order reaction (b--> products) has a rate constant of 1.70×10^-3 m^-1*s^-1 at 27 degrees c and an initial half-life of 296 s. what is the concentration of the reactant b after one half-life?

A.  14 min

B . 0.995 M

Explanation:

A.

Using integrated rate law for first order kinetics as:

Where,  

is the concentration at time t

is the initial concentration

Given:

The final concentration is dropped to 6.25 % of the initial concentration. SO,

= 0.0625

k =

So,

Also, 1 s = 1/60 minutes.

So,

14 minutes it takes for the concentration of the reactant to drop to 6.25% of the original concentration.

B.

(a) Half life expression for second order kinetic is:

Where,  

is the initial concentration = ?

k is the rate constant = M⁻¹s⁻¹

Half life = 296 s

So,

Half life is the time at which the concentration of the reactant reduced to half. So, concentration remains = = 0.995 M

when—without warning—something provokes your anger, you may struggle not to succumb to it. since what typically makes you mad is feeling powerless in the face of what seems unfair, your anger is mostly an attempt at a “quick fix” to right the balance. it’s as though you’re raising a fist in protest, proclaiming that you’re not going to capitulate to such injustice.

there are, however, a multitude of problems related to this immediate, push-back reaction of anger. and probably the key one is that almost never does it resolve the issue that gave rise to it. such reactive anger is probably best understood as self-defeating. as david burns, the author of the seminal self- book feeling good, observes: if realistically, acting on your anger is to make any sense, it needs to meet two criteria—which, in almost every case, is frankly impossible. that is, your anger must:

be directed toward a person who has intentionally (and needlessly) behaved in a hurtful way toward you; and

be beneficial or advantageous to you (i.e., assist you in achieving a desired goal).

i think you’ll agree that only rarely can you claim that your anger is both warranted and , whether to yourself or the relationship.

so let me offer you a two-step alternative to abandoning your better judgment and giving in to the temptation of anger—one that should neutralize your anger in seconds. or, when you’re really angry, in minutes.

but keep in mind that you must really want to execute these steps, be sufficiently motivated to perform them. which means overcoming more unconscious resistance than you might ever have imagined. because there are many immediate “advantages” of anger that can interfere with your resolve, i’ll suggest a few of them that might interfere with your employing this powerful method to rid yourself of counter-productive anger.

explanation: