im not sure which one to answer, and i can hardly see the text.
3Si + 2N2 --> Si3N4 (as given)
n(Si) = m/MM = 38.25/28.085 = 1.3619 mol
n(N2) = 14.33/2*14.007 = 0.5115 mol
Therefore, N2 is limiting and Si is in excess
The molar ratio of 2N2:Si3N4 is 2:1
So, 0.0575 mol of silicon nitride is formed (dividing 0.5115 by 2)
m of silicon nitride= n*mm = 0.0575*140.283 = 8.06627... g
= 8.066g (4 significant figures)
(hopefully it is right, but double check in case i did something wrong) :)
Answer:
The frequency is 
Explanation:
From the question we are told that
The energy required to ionize boron is 
Generally the ionization energy of boron pre atom is mathematically represented as

Here
is the Avogadro's constant with value 
So

=> 
Generally the energy required to liberate one electron from an atom is equivalent to the ionization energy per atom and this mathematically represented as

=> 
Here h is the Planks constant with value 
So

=> 