The groups (left to right) are numbered from 1 to 18. they arent numbered any other way.
period (up to down.) are numbered from 1-7
Answer:
= 72900 years
Explanation:
- The half-life is the time taken by a radioactive material to decay by half the original amount.
- The half-life of plutonium-239 is 24300 years which means it takes 24300 years to decay by half the original amount.
To calculate the time taken for a mass of 8 kg to decay to 1 kg we use;
New mass = Original mass x (1/2) ^n, where n is the number of half-lives
Therefore;
1 kg = 8 kg × (1/2)^n
1/8 = (1/2)^n
solving for n;
n =3
Therefore;
Time = 3 × 24300 years
= 72900 years
It will, therefore, take 72900 years for 8 kg of plutonium-239 to decay to 1 kg.
The correct answer that explains similarities between metal and Metalloids as regards the question is They both conduct electricity
- Metalloids can be regarded as elements that are similar to metals, this is because they posses valence orbitals which is described as highly delocalized over macroscopic volumes.
- As a result of this they can serve as electrical conductors.
- metalloids posses small energy gap which is located between the valence band as well as the conduction band, as a result of this they are considered as intrinsic semiconductors when compare to pure conductors like metal.
- Example of metal is Calcium, sodium and that of Metalloids are silicon and germanium
Therefore, metal and Metalloids are similar because of their conductivity of electricity
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Answer:
C. 0.4.
Explanation:
<em>∵ mole fraction of acetic acid (X acetic acid) = (no. of moles acetic acid)/(total no. of moles) = (no. of moles acetic acid)/(no. of moles of acetic acid + no. of moles of water).</em>
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- no. of moles of acetic acid = 2, no. of moles of water = 3.
- Total no. of moles = no. of moles of acetic acid + no. of moles of water = 2 + 3 = 5.
<em>∴ mole fraction of acetic acid (X acetic acid) = (no. of moles acetic acid)/(total no. of moles) =</em> (2)/(5)<em> = 0.4.</em>
