Answer:
The molecular formula is As4S6
Explanation:
Step 1: Data given
melting point = 320 °C
The molecules of the vapor phase are found to effuse through a tiny hole at 0.28 times the rate of effusion of As
Step 2: Calculate mean square speed of Ar
µAr = √(3RT/MM)
µAr = √((3*8.314*593)/39.948*10^-3)
µAr = 608.48
Step 3: Calculate the mean speed of arsenic (III) sulfide:
µ = 0.28*µAr = 0.28 * 608.48 =170.37 m/s
Step 4: Calculate molar mass of arsenic (III) sulfide:
µ = √((3R*T)/MM)
170.37 m/s = √((3*8.314 kg*m²/s²*mol*K * 593K)/MM)
170.37² =((3*8.314 kg*m²/s²*mol*K * 593K)/MM)
MM = (3*8.314 kg*m²/s²*mol*K * 593K)/(170.37²)
MM =0.5096 kg /mol = 509.6 g/mom
The empirical formule for As(III) sulfide = As2S3
As2S3 has a molar mass of 246.035 g/mol
Step 5: Calculate molecular formula of As(III) sulfide
n = 509.6 /246.035
n = 2.07 ≈ 2
This means we have to multiply the empirical formule by 2.
The molecular formula is As4S6
