We are given with the mass of Arsine (
The mass of arsine is 15g
there is a relation between moles, mass and molar mass of any compound which is

The molar mass of Arsine = atomic mass of As + 3X atomic mass of H
the molar mass of Arsine = 74.92 + 3X 1 = 77.92 g/mol
Let us calculate the moles as

Answer: The temperature of the gas reduced to 400K.
Explanation:
Stated that ; The pressure remains the same, that is initial and final pressure equals 1atm.
Applying Charles Law

Initial volume V1 = 1
Final volume V2 = 1/2 (halved)
Initial temperature T1 =800K
Final temperature T2 = ?
(1/800) = (1/2)/T2
T2 = 800/2
T= 400K
Therefore, when the volume is halved, the temperature reduced also to half ( 400K)
B. I’m sorry if I’m wrong ! Wasn’t sure about this question .