The amount of substance present in a certain sample can be calculated through the equation,
A(t) = A(o)(0.5)^(t/h)
where At is the amount now, Ao is the original amount, t is the number of years and h is the half-life.
For a substance to at most 50% of the original amount, we get the half-life value.
At/Ao = 0.5 = 0.5^(4.5/h)
h = 4.5 billion.
All values below 4.5 billion as half-life are accepted. From the given list, the substances that would be less than 50% now are:
<em>Uranium - 238 ; Uranium -235 and ; Postassium-40</em>
Increasing the pressure will increase the reaction rate because it will force the particles to be closer together, and so the likelihood of particles colliding increases. Increasing the temperature can also increase the rate of a reaction because the particles will be more energised and more likely to move around and collide.
the answer is either model, or concept
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Answer:
Carbon-14 is an isotope of carbon and differs in the number of neutrons in their nucleus.
Explanation:
all isotopes have the same number of protons and electrons, but differ in the number of neutrons. They have identical chemical behaviour but with different atomic masses and physical properties