This question is testing to see how well you understand the "half-life" of radioactive elements, and how well you can manipulate and dance around them. This is not an easy question.
The idea is that the "half-life" is a certain amount of time. It's the time it takes for 'half' of the atoms in any sample of that particular unstable element to 'decay' ... their nuclei die, fall apart, and turn into nuclei of other elements.
Look over the table. There are 4,500 atoms of this radioactive substance when the time is 12,000 seconds, and there are 2,250 atoms of it left when the time is ' y ' seconds. Gosh ... 2,250 is exactly half of 4,500 ! So the length of time from 12,000 seconds until ' y ' is the half life of this substance ! But how can we find the length of the half-life ? ? ?
Maybe we can figure it out from other information in the table !
Here's what I found:
Do you see the time when there were 3,600 atoms of it ?
That's 20,000 seconds.
... After one half-life, there were 1,800 atoms left.
... After another half-life, there were 900 atoms left.
... After another half-life, there were 450 atoms left.
==> 450 is in the table ! That's at 95,000 seconds.
So the length of time from 20,000 seconds until 95,000 seconds
is three half-lifes.
The length of time is (95,000 - 20,000) = 75,000 sec
3 half lifes = 75,000 sec
Divide each side by 3 : 1 half life = 25,000 seconds
There it is ! THAT's the number we need. We can answer the question now.
==> 2,250 atoms is half of 4,500 atoms.
==> ' y ' is one half-life later than 12,000 seconds
==> ' y ' = 12,000 + 25,000
y = 37,000 seconds .
Check:
Look how nicely 37,000sec fits in between 20,000 and 60,000 in the table.
As I said earlier, this is not the simplest half-life problem I've seen.
You really have to know what you're doing on this one. You can't
bluff through it.
The biological compounds that are nonpolar and insoluble in water are lipids. It is a group of molecules that are naturally occurring which includes sterols, waxes, fats, fat-soluble vitamins and the like. These molecules are nonpolar molecules so basically the cannot be dissolved in a polar solvent like water.
Answer:
what type of question?
Explanation:
whats your favorite color???
Answer:
Thermal decomposition or cracking
Explanation:
Petroleum is a mixture of hydrocarbons which are usually formed naturally. Petroleum undergo a host of chemical reactions. One of such is thermal decomposition or cracking.
Cracking is used in the petroleum industry to covert heavy fractions to more useful lighter ones.
When petroleum is subjected to high temperature and pressure, and in the presence of catalyst, the long chain type of petroleum will decompose into more useful smaller and lighter molecules.
Example is given below:
C₁₅H₃₂ → C₈H₁₈ + C₃H₆ + 2C₂H₄
Answer:
Explanation:
In this problem, we need to convert 
to km².
We know that,
1 km = 1000 m
⇒ 1 km² = 10⁶ m²
So,
So, is equal to .
