a 66.5 ml glass tube weighs 28.0517g when evacuated and 28.1222g when filled with the hydrocarbon gas acetylene at 749.3 mm Hg and 20.02 C

Question

Empty glass tube weighs 28.0517g

28.1222g when filled with the hydrocarbon gas

weight of gaseous hydrocarbon acetylene = 28.1222g - 28.0517g= 0.0705g

From ideal gas equation,

PV=nRT

0.986 atm * 0.0665 L =  n * 0.0821* 293.17 K

n = ( 0.986 atm * 0.0665 L)/ ( 0.0821* 293.17 K)= 0.00272418047 moles

n = No of moles of acetylene= amount in grams of acetylene/ molar mass  of acetylene in g/mol

0.00272418047 moles =  0.0705g/ molar mass  of acetylene

molar mass  of acetylene = 0.0705g/ 0.00272418047 moles= 25.9 g/mol

Answer 1

mass acetylene = 28.1222 g - 28.0517 g = 0.0705 g

PV = nRT

n = PV/RT = (749.3 mm Hg)(0.0665 L) / (62.36 Lmm/Kmol)(293.17)

n = 0.0027255 moles

molar mass = g / moles

molar mass = 0.0705 g / 0.0027255 mols

molar mass = 25.87 g/mol = 25.9 g / mole

YOU ARE CORRECT