3)
V = 450 mL = 0.450 L
T =25 +273 = 298 K
P = 740 mmHg = 0.974 atm
P V = n R T
0.974 x 0.450 = n x 0.0821 x 298
n = 0.0179
moles of H2 = 0.0179
2 X + 6 HCl ----------------------> 2 XCl3 + 3 H2
3 moles H2 --------------------> 2 moles X
0.0179 moles H2 ------------> ??
moles of X = 2 x 0.0179 / 3 = 0.01194
moles of X = 0.01194
mass of X = 0.605 g
moles = mass / molar mass
0.01194 = 0.605 / molar mass
molar mass = 50.7 g / mol
molar mass of X = 50.7 g /mol
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