The formula for osmotic pressure (Pi) is
color(blue)(bar(ul(|color(white)(a/a)Pi = MRTcolor(white)(a/a)|)))" "
where
M = molarity of the solution
R = the Ideal Gas Constant
T = the temperature of the solution
We can rearrange the above equation to get
M= Pi/(RT)
In your problem,
Pi = 1.5 color(red)(cancel(color(black)("Torr"))) × "1 atm"/(760 color(red)(cancel(color(black)("Torr")))) = "0.001 97 atm"
R = "0.082 06 L·atm·K"^"-1""mol"^"-1"
T = "(25 + 273.15) K" = "298.15 K"
∴ M = ("0.001 97" color(red)(cancel(color(black)("atm"))))/("0.082 06 L" color(red)(cancel(color(black)("atm·K")))·"mol"^"-1" × 298.15 color(red)(cancel(color(black)("K")))) = 8.07 × 10^"-5" color(white)(l)"mol/L"
"Moles of myoglobin" = "0.005 00" color(red)(cancel(color(black)("L"))) × 8.07 × 10^"-5"color(white)(l) "mol"·color(red)(cancel(color(black)("L"^"-1"))) = 4.03 × 10^"-7"color(white)(l) "mol"
"Molar mass" = "mass"/"moles" = (3.50 ×10^"-3" color(white)(l)"g")/(4.03 × 10^"-7" "mol") = "8700 g/mol"
Note: I must be having a brain burp here. This is about half the recognized value for human, horse, and sperm whale myoglobin. Where is my mistake?
