To solve the question, there is a need to use the equation:
PV = nRT
(894.6/760) × 1.18 = n × 0.0821 × (273 + 44.1)
By solving we get:
Total moles, n = 0.053
Assume, the moles of argon as a and of hydrogen as b,
So,
40 × a + 2 × b = 1.25 --------- (i)
a + b = 0.053 ------- (ii)
By solving i and ii we get:
a = 0.03,
Thus, mole fraction of Ar = XAr = 0.03/0.053 = 0.57
So,
Partial pressure of Ar = 894.6 × XAr = 894.6 × 0.57 = 509.92 mm Hg