The half-life of Th-232 is 1.405 × 10¹⁰ years
Time elapsed = 2.8 x 10⁹ years
Equation of radioactive decay:
A = A₀ = (1/2)^ t/t₁/₂
where A₀ is the initial amount, A is the amount after time t, t₁/₂ is the half file
The fraction of thorium-232 that remains in the rock after 2.8 billions years is,
A/A₀ = (1/2) ^ (2.8 x 10⁹/ 1.405 × 10¹⁰) = 0.871
Therefore, the percentage of thorium-232 in the rock that was dated at 2.8 billions year = 87.1%
<h3>
Answer:</h3>
= 19.712 kJoules
<h3>
Explanation:</h3>
- Heat of vaporization refers to the amount of heat required to change a unit mass of a substance from liquid to gaseous state without change in temperature.
To calculate the amount of heat, we use,
Amount of heat = Mass × Heat of vaporization
Q = m×Lv
Given;
Mass of liquid Zinc = 11.2 g
Lv of liquid Zinc = 1.76 kJ/g
Therefore;
Q = 11.2 g × 1.76 kJ/g
= 19.712 kJ
Thus, the amount of heat needed to boil 11.2 g of zinc is 19.712 kilo-joules.
Explanation:
The combustion of ethanol is best represented by the equation below:
C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O + heat
Combustion process is very common among hydrocarbons.
Ethanol is an alcohol and in the presence of oxygen it will combust.
In combustion heat energy is always released into the environment.
C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O + heat
We see that ethanol combines with oxygen to give carbon dioxide and water in the reaction above.
The heat produced signifies that the reaction is exothermic in nature.
learn more:
Combustion brainly.com/question/11200282
#learnwithBrainly
True is correct answer.
Polymerization is the process of linking it has a smaller molecules to form has a long chains of higher molecular weight.
Hope it helped you.
-Charlie
Answer:
0.000399316 g
Explanation:
We can start with the <u>molar fraction</u> for each isotope:
We can say that the abudandance of 
is an unknow value <u>"X"</u> and the molar fraction of 
is <u>"Y"</u>. We have to keep in mind that the molar fractions can be added:
Y + X = 1
So, we can put the molar fraction of in terms of , so:
Y=1-X
So, we will have the <u>molar fraction of each isotope</u>:
: X-1
: X
And the <u>atomic mass</u>:
: 21.9944
: 22.9898
If we multiply the molar mass by the each atomic mass of each isotope we will have:
Now we can solve for "X" :
The molar fraction of is <u>0.999749</u>. Now we can calculate the molar fraction of , so:
Now, if we multiply the molar fraction by the mass we can find the <u>mass</u> of , so:
The mass of is 0.000399316 g
I hope it helps!
