<span>Boron has a lot of different isotopes, most of which having a very short half life (ranging from 770 milliseconds for Boron-8 down to 150 yoctoseconds for boron-7). But the two isotopes Boron-10 and Boron-11 are stable with about 80.1% of the naturally occurring boron being boron-11 and the remaining 19.9% being boron-10. The weighted average weight of those 2 isotopes has the value of 10.81.
The reason they use the average mass of an element for it's atomic weight is because elements in nature are rarely single isotopes. The weighted average allows us to easily compare relative number of atoms of one element against relative numbers of atoms of another element assuming that the experimenters are getting isotope ratios close to their natural ratios.</span>
Atoms are the smallest building block that can affect things, and are many many times smaller then cells. our eyes are not designed to see such small things
Answer:
Theoretical yield: 2.75g of paranitroaniline
Percentage yield: 54.5%
Explanation:
In strong-acid medium, acetanilide (Molar mass: 135.16g/mol) reacts producing para-nitroaniline (138.12g/mol) in a 1/1 reaction.
Theoretical yield of para-nitroaniline is the mass produced assuming a yield of 100%. That is:
2.7g acetanilide × (1mol / 135.16g) = 0.020 moles of acetanilide.
Assuming a yield of 100% are 0.020 moles of paranitroaniline. Theoretical yield is:
0.020 moles × (138.12g / mol) =
<h3>Theoretical yield: 2.75g of paranitroaniline</h3><h3 />
Percentage yield is:
(Actual yield / theoretical yield) × 100
Actual yield was 1.5g and percentage yield will be:
Percentage yield: (1.5g / 2.75g) × 100
<h3>Percentage yield: 54.5%</h3>
Answer:
A open system
I think plz tell me if i'm wrong
Explanation:
Physical change
iron nail have high melting point, thus, when it is heated, it will not melt very easily.
chemical change
iron nail can rust due to the exposure to the air(oxygen). iron in the nail and oxygen in the air will react together to form iron oxide(rust).
furthermore, the reaction is irreversible.