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3 years ago

Iodine-131 is a radioactive isotope. after 9.00 days, 46.0% of a sample of 131i remains. what is the half-life of 131i?

1 answer:

6 0

For this problem, we use the integrated rate law for first order radioactive decay which is expressed as follows:

An = Aoe^-kt

where An is the amount left after time t, Ao is the initial amount and k is a constant.

We need to calculate first the value of k from the given ration An/Ao and the time it reached that ration. We do as follows:

An = Aoe^-kt
0.46= e^-k(9)
k = 0.0863 / day

At half life, the remaining substance would be equal to one-half of the original so that An/Ao would be equal to 1/2 or 0.50. We calculate the half-life as follows:

An = Aoe^-kt
0.50 = e^-0.0863(t)
t = 8.03 days

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Choose a likely identity for X, Y, and Z in these structures. A central X atom is bonded to two chlorine atoms through single bo

natka813 [3]

Complete Question

The complete question is shown on the first uploaded image

Answer:

X is Be

Y is B

Z is O

Explanation:

In order to understand the solution, we need to that the an element form a bond based on

1 The number of valence electron available in its atom

2 The number of electron it require to attains its stable state i.e its Octet state

The number of valence electron for each of the option are

F = 7, N = 5 , O = 6 , C = 4 , B = 3 , Be = 2

Considering the first element

We see that X is donating two valence electron in its atom and it is donating it to 2 Cl as Cl only requires a single electron to achieve its stable state

Now looking option we can see that Be has two valence electron in it atom and in order for it to attain its stable state it needs to release the electron so the correct option for this question is Be

Considering the second element

We see that Y is donating three valence electron in its atom and it is donating it to 3 Cl as Cl only requires a single electron to achieve its stable state

Now looking option we can see that B has three valence electron in it atom and in order for it to attain its stable state it needs to release the valence electron so the correct option for this question is B

Considering the second element

We see that Z is donating two valence electron in its atom and it is donating it to 2 Cl as Cl only requires a single electron to achieve its stable state, also Z has 2 lone-pair valence electron

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3 years ago

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Softa [21]

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3 years ago

Read 2 more answers

A reasonable pka for a weak base is: 10.3 0.9 5.8 7.4 13.1

andriy [413]

Answer:

0.9

Explanation:

The pka represents the force by which the molecules need to dissociate for the acids ,

Hence , lower the pka stronger will be the acid and that therefore will dissociate completely and vice versa , for a weak acid higher the pka .

And in case of a base , it will be completely reversed , lower pKa , weaker base ,

and higher pKa , stronger base .

From the data of the question ,

0.9 is the lowest value of the pKa , hence , weakest base .

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3 years ago