Chemistry College

The half-life of the radioactive isotope polonium-218 is 3.05 minutes.

How long will it take for the activity of a sample of polonium-218 to decrease from 2.81E4 Ci to 3.52E3 Ci?

Answers

Answer 1

Answer: It will take 9.13 minutes for the sample.

Explanation:

Expression for rate law for first order kinetics is given by:

[tex]t=\frac{2.303}{k}\log\frac{a}{a-x}[/tex]

where,

k = rate constant  

t = age of sample

a = initial amount of the reactant = [tex]2.81\times 10^4[/tex]

a - x = amount left after decay process = [tex]3.52\times 10^3[/tex]

a) for completion of half life:

Half life is the amount of time taken by a radioactive material to decay to half of its original value.

[tex]t_{\frac{1}{2}}=\frac{0.693}{k}[/tex]

[tex]k=\frac{0.693}{3.05min}=0.227min^{-1}[/tex]

b) for activity to decrease from 2.81E4 Ci to 3.52E3 Ci:

[tex]t=\frac{2.303}{0.227}\log\frac{2.81\times 10^4}{3.52\times 10^3}[/tex]

[tex]t=9.13min[/tex]

Thus it will take 9.13 minutes for the sample.

[tex]t_{99.9}=40min[/tex]

The time after which 99.9% reactions gets completed is 40 minutes

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Answers

Answer:

carbon

Explanation:

Many organisms use carbon to make calcium carbonate, a building material of shells and skeletons. Other chemical processes create calcium carbonate in the water. The using up of carbon by biological and chemical processes allows more carbon dioxide to enter the water from the atmosphere.

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Answers

Answer:

Natural selection changes how well a species can survive in an environment.

Explanation:

I'm not the best at biology, but natural selection a term we use that's describes nature's way of choosing the strongest to survive. The species with the strongest adaptations will survive while the others will die off. For example, if a school of fish was forced to live in a colder habitat than usual, over many years some fish will adapt to that environment and be able to withstand it. But, some fish won't get those adaptations and be killed off. But, future generations will be born with that ability to withstand the cold environment and it would become normal. So, natural selection changes the way a species lives. Hope this helps

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