A 0.268g sample of a polypeptide was dissolved in water and made up to a volume of 160mL at 31.0°C. At this temperature the osmotic pressure of this solution was 4.41mmHg. Calculate the molecular mass of the polypeptide
pi = MRT
4.41mm/760mm = M*0.08205*(273+31)
0.00580/0.08205*304 = M = moles/L 0 000233
0.000233 = mols/0.160 L. Solve for moles, then moles = grams/molar mass. You have moles and grams. solve for molar mass.
Confirm those calculations.
To calculate the molecular mass of the polypeptide, we can use the formula:
𝑀 = 𝑅𝑇/𝑃𝑉
Where:
𝑀 = Molecular mass of the polypeptide (in g/mol)
𝑅 = Ideal gas constant (0.0821 L·atm/mol·K or 8.314 J/mol·K)
𝑇 = Temperature in Kelvin (31.0°C + 273.15 = 304.15 K)
𝑃 = Osmotic pressure in atm (4.41 mmHg ÷ 760 mmHg/atm = 0.0058 atm)
𝑉 = Volume in liters (160 mL ÷ 1000 mL/L = 0.160 L)
Plugging in these values, we can calculate the molecular mass:
𝑀 = (0.0821 L·atm/mol·K) × (304.15 K) / (0.0058 atm × 0.160 L)
𝑀 ≈ 39,270 g/mol
Therefore, the molecular mass of the polypeptide is approximately 39,270 g/mol.
To calculate the molecular mass of the polypeptide, we can use the equation:
M = (RT) / (PV)
Where:
M = molecular mass (in grams per mole)
R = ideal gas constant (0.0821 L·atm/(K·mol) or 8.314 J/(K·mol))
T = temperature (in Kelvin)
P = osmotic pressure (in atm)
V = volume of the solution (in liters)
First, let's convert the given values:
Temperature = 31°C = 273.15 + 31 = 304.15 K
Osmotic pressure = 4.41 mmHg = 4.41 / 760 atm
Next, we need to convert the volume from milliliters to liters:
Volume = 160 mL = 160 / 1000 L = 0.16 L
Now, we can plug in these values into the equation to find the molecular mass:
M = ((0.0821 L·atm/(K·mol)) * (304.15 K)) / ((4.41 / 760 atm) * (0.16 L))
After performing the calculation, the molecular mass of the polypeptide is obtained.