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kvv77 [185]
3 years ago
11

How many half-lives must elapse until 84 % of a radioactive sample of atoms has decayed? -g?

Chemistry
1 answer:
Ivahew [28]3 years ago
4 0
Half-life is the time required for decay of 50% of radio-active nuclei.

Thus, when radio-active material crosses 1st half-life, 100/2 = 50% radio-active material is left and remaining 50% is elapsed.

When, when radio-active material crosses 2nd half-life, 50/2 = 25% radio-active material is left and remaining 75% is elapsed.

When radio-active material crosses 3rd half-life, 25/2 = 12.5% radio-active material is left and remaining 87.5% is elapsed.

Thus, 2 <span>half-lives must elapse until 84 % of a radioactive sample of atoms has decayed.</span>
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From the relative rates of effusion of ²³⁵UF₆ and ²³⁸UF₆ , find the number of steps needed to produce a sample of the enriched f
Dafna11 [192]

The number of steps required to manufacture a sample of the 3.0 mole%  ²³⁵U enriched fuel used in many nuclear reactors from the relative rates of effusion of ²³⁵UF₆ and ²³⁸UF₆. ²³⁵U occurs naturally in an abundance of 0.72% are :  mining, milling, conversion, enrichment, fuel fabrication and electricity generation.

<h3>What is Uranium abundance ? </h3>
  • The majority of the 500 commercial nuclear power reactors that are currently in operation or being built across the world need their fuel to be enriched in the U-235 isotope.
  • This enrichment is done commercially using centrifuges filled with gaseous uranium.
  • A laser-excitation-based method is being developed in Australia.
  • Uranium oxide needs to be changed into a fluoride before enrichment so that it can be treated as a gas at low temperature.
  • Uranium enrichment is a delicate technology from the perspective of non-proliferation and needs to be subject to strict international regulation. The capacity for world enrichment is vastly overbuilt.

The two isotopes of uranium that are most commonly found in nature are U-235 and U-238. The 'fission' or breaking of the U-235 atoms, which releases energy in the form of heat, is how nuclear reactors generate energy. The primary fissile isotope of uranium is U-235.

The U-235 isotope makes up 0.7% of naturally occurring uranium. The U-238 isotope, which has a small direct contribution to the fission process, makes up the majority of the remaining 99.3%. (though it does so indirectly by the formation of fissile isotopes of plutonium). A physical procedure called isotope separation is used to concentrate (or "enrich") one isotope in comparison to others. The majority of reactors are light water reactors (of the PWR and BWR kinds) and need their fuel to have uranium enriched by 0.7% to 3-5% U-235.

There is some interest in increasing the level of enrichment to around 7%, and even over 20% for particular special power reactor fuels, as high-assay LEU (HALEU).

Although uranium-235 and uranium-238 are chemically identical, they have different physical characteristics, most notably mass. The U-235 atom has an atomic mass of 235 units due to its 92 protons and 143 neutrons in its nucleus. The U-238 nucleus has 146 neutrons—three more than the U-235 nucleus—in addition to its 92 protons, giving it a mass of 238 units.

The isotopes may be separated due to the mass difference between U-235 and U-238, which also makes it possible to "enrich" or raise the proportion of U-235. This slight mass difference is used, directly or indirectly, in all current and historical enrichment procedures.

Some reactors employ naturally occurring uranium as its fuel, such as the British Magnox and Canadian Candu reactors. (By contrast, to manufacture at least 90% U-235, uranium needed for nuclear bombs would need to be enriched in facilities created just for that purpose.)

Uranium oxide from the mine is first transformed into uranium hexafluoride in a separate conversion plant because enrichment operations need the metal to be in a gaseous state at a low temperature.

To know more about Effusion please click here : brainly.com/question/22359712

#SPJ4

7 0
2 years ago
PLEASE HELP ME I BEG YOU
VladimirAG [237]

The average kinetic energy of 1 mole of a gas at -32 degrees Celsius is:
 
3.80 x 103 J

The relationship between volume and temperature of a gas, when pressure and moles of a gas are held constant, is: V*T = k.

FALSE

The relationship between moles and volume, when pressure and temperature of a gas are held constant, is: V/n = k. We could say then, that:
If the moles of gas are tripled, the volume must also triple.


 If the temperature and volume of a gas are held constant, an increase in pressure would most likely be caused by an increase in the number of moles of gas.

TRUE

If the vapor pressure of a liquid is less than the atmospheric pressure, the liquid will not boil.

TRUE


35 - AB

36 -  BD

33 - true

34 - False

20 - 6

21 - orthohombic


4 0
3 years ago
Hi! I'm on the last question of my homework and I'm stuck on it and was wondering if anyone could help me
Semmy [17]
I am not sure but this is what I think

This question uses the formula connecting mass, density and volume
Which is Density= Mass/Volume

Convert the mass in g
92.5 kg = 92,500g


7.87g/ml = 92,500/ Volume
Volume= 92,500/7.87
= 11,753.5 ml

Now since we have to give the answer in liters we can just divide by 1000 and get
11.75 litres

5 0
2 years ago
Dna contains the template needed to copy itself, but it has no catalytic activity in cells. what catalyzes the formation of phos
Over [174]
I am sure it is DNA polymerase.
I'm a bio major, hope I helped :)
4 0
3 years ago
Which of these electron transitions correspond to absorption of energy and which to emission?
Keith_Richards [23]

The electron transitions representing absorption of energy are:

(a) n = 2 to n = 4

(d) n = 3 to n = 4

and those which represents emissions of energy are:

(b) n = 3 to n = 1

(c) n = 5 to n = 2

An electron emits energy when it jumps from a higher energy level to a lower energy level transitions.

An electron absorbs energy to jump from a lower energy level to a higher energy level transitions.

(a) n = 2 to n = 4

Here, the initial level (2) is lower than the final level (4).

Hence energy is absorbed.

(b) n = 3 to n = 1

Here, the initial level (3) is higher than the final level (1).

Hence energy is released.

(c) n = 5 to n = 2

Here, the initial level (5) is higher than the final level (2).

Hence energy is released.

(d) n = 3 to n = 4

Here, the initial level (3) is lower than the final level (4).

Hence energy is absorbed.

The question is incomplete. Find the complete question here:

Which of these electron transitions correspond to absorption of energy and which to emission?

(a) n = 2 to n = 4

(b) n = 3 to n = 1

(c) n = 5 to n = 2

(d) n = 3 to n = 4

Learn more about electron transitions at brainly.com/question/2079874

#SPJ4

4 0
1 year ago
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