There are two naturally occurring isotopes of chlorine, 35_Cl (34.9688 amu) and
ID: 1023513 • Letter: T
Question
There are two naturally occurring isotopes of chlorine, 35_Cl (34.9688 amu) and 37_CI (36.9651 amu). While modern measurements of the percentage of each isotope of chlorine in nature are based on mass spectrometry, an approximate value for this percentage can be found from measurements on gases containing chlorine. The density of hydrogen chloride gas (HCI), measured at T=18.3 degree C and p=774.5 torr, is rho=1.554 g/L. Based on this information, and assuming that HCL obeys the ideal gas law. find the percentage of the 35_CI isotope in the sample of HCI. Note that naturally occurring hydrogen can be assumed to be all the 1_H isotope (1.0078 amu). Compare your result to the value determined using mass spectrometry, percent 35_Cl= 75.5 %.Explanation / Answer
PV = nRT
n = m / M = mass /Molecular weight
P = 774.5 torr = 1 atm
T = 18.3 = 291.3 K
P = m RT / V M.W
P = dRT / M.W
we know all lets find M.W
M.W = 36.47
x*34.9688 + 1 -x *36.9651 = 36.47
x = 0.24 ==> 24.8% of 35Cl
==> 75.2%of 37Cl are present