Question #a065d

1 Answer
Jul 21, 2017

Answer:

The molecular formula is a) #"MCl"_4#.

Explanation:

Step 1. Calculate the molar mass of the compound

To do this, we can use the Ideal Gas Law:

#color(blue)(bar(ul(|color(white)(a/a)pV = nRTcolor(white)(a/a)|)))" "#

Since #n = m/M#. we can write

#pV = m/MRT#

And we can rearrange this to

#M = (mRT)/(pV)#

STP is defined as 0 °C and 1 bar, so

#M = ("16.96 g" × "0.083 14" color(red)(cancel(color(black)("bar·L·K"^"-1")))"mol"^"-1" × 273.15 color(red)(cancel(color(black)("K"))))/(1 color(red)(cancel(color(black)("bar"))) × 1 color(red)(cancel(color(black)("L")))) = "385.16 g·mol"^"-1"#

Step 2. Calculate the formula of the compound

Your compound contains 37.321 % #"Cl"#.

(a) Calculate the mass of #"Cl"# in 1 mol of the compound.

#"Mass of Cl" = 385.16 color(red)(cancel(color(black)("g compound"))) × "37.321 g Cl"/(100 color(red)(cancel(color(black)("g compound")))) = "143.74 g Cl"#

(b) Calculate the moles of #"Cl"#

#"Moles of Cl" = 143.74 color(red)(cancel(color(black)("g Cl"))) × "1 mol Cl"/(35.45 color(red)(cancel(color(black)("g Cl")))) = "4.055 mol Cl" ≈ "4 mol Cl"#

∴ The formula of the compound is #"MCl"_4#.