The answer will be d i just took the test and got it correct
Every electron shell, designated by "n", has a specific number of electron subshells. The shell number has values equivalent to natural numbers (1, 2, 3, 4...), while the subshells are s, p, d and f.
The subshell that does not exist within the third shell (n = 3) is the f subshell. The energy of the f subshell is too high and cannot be accommodated in the third shell.
Explanation:
Formula for compressibility factor is as follows.
z = 
where, z = compressibility factor for helium = 1.0005
P = pressure
= molar volume
R = gas constant = 8.31 J/mol.K
T = temperature
So, calculate the molar volume as follows.

= 
= 0.0056 
As molar mass of helium is 4 g/mol. Hence, calculate specific volume of helium as follows.

= 
= 0.00139 
= 0.00139 
= 1.39 
Thus, we can conclude that the specific volume of Helium in given conditions is 1.39
.
Answer: 48.95g
Explanation:
no. of moles of Cl2 = 39/(2*35.5) = 0.55 mol
no. of moles of Al = 34/27 = 1.26 mol
hence, aluminium is in excess so we'll do calculation using no. of moles of Cl2 as it will be the only reactant to be used up completely. So,
no of moles of AlCl3 = 2/3 * (0.55) = 0.367 mol
hence amount of AlCl3 = 0.367 * (27+3*35.5) = 48.95g