Aradioactive element of mass 20.0g was isolated and stored. it was discovered after 40days that 2.5g of the element remained undecayed. calculate the half life of the element.

Half life = 13.3 days

Explanation:

Given data:

Mass of element = 20.0 g

After 40 days a mass left = 2.5 g

Half life of element = ?

Solution:

At time zero = 20.0 g

At first half life = 20.0 g/2 = 10.0 g

At second half life = 10.0/2 = 5.0 g

At third half life = 5.0 g/ 2 = 2.5 g

Half life:

Half life = T elapsed / number of half lives

Half life = 40 days / 3

Half life = 13.3 days

acid rain does not usually kill trees directly. instead, it is more likely to weaken the trees by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowly released from the soil. the main atmospheric pollutants that affect trees are nitrates and sulphates.

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.