Answer : The mass of 
required is 18.238 grams.
Explanation : Given,
Mass of 
= 83.10 g
Molar mass of = 146 g/mole
Molar mass of = 256.52 g/mole
The balanced chemical reaction is,
First we have to determine the moles of .
Now we have to determine the moles of .
From the balanced chemical reaction we conclude that,
As, 8 moles of produced from 1 mole of
So, 0.569 moles of produced from 
mole of
Now we have to determine the mass of .
Therefore, the mass of required is 18.238 grams.
7.91 g/ml is the density of the iron piece of 28.5 gms.
Explanation:
The density of a substance is defined as the volume it occupies. It tells the matter present in a substance.
The density is mass per unit volume and is denoted by p.
The formula for density is given by:
density (p) = 
Data given is :
mass= 28.5 grams
V1 = 45.5 ml
V2= 49.1 ml
The initial volume of water was 45.5 ml, when iron piece of 28.5 grams was added the final volume was 49.1 ml.
Putting the values in the equation of density
p = 
p = 7.91 g/ml
Since iron is a dense material it will occupy less volume
Your answer is sublimation.
It need "3 electrons" to have a stable electronic configuration.
'cause it has 5 electrons in it's outer shell & every atom needs 8 electrons. So, it requires 3 more!
Hope this helps!
