# What is the Molar Mass of an Enzyme with a Given Osmotic Pressure?

• Benzoate
In summary, a 2.02-g sample of an enzyme in a 6.00-mL solution with an osmotic pressure of 0.123 atm at 298K has a molar mass of approximately 67,000 g/mol, which is within the usual range for enzymes. The calculation was done using the equation pi=MRT and a conversion of concentration to grams/mol.
Benzoate

## Homework Statement

A 2.02-g sample of an enzyme is used to make a 6.00-mL solution. What is the molar mass of the enzyme if the osmotic pressure of the solution at 298K is 0.123 atm? Note that enzymes are nonelectrolytes

## Homework Equations

pi=MRT , R=.0821 L*atm*K^1-*mol^1-

## The Attempt at a Solution

pi=MRT => pi/RT=M=.123 atm/(298K)(.0821)=.00503 M

to find molar mass, I'd want to convert my concentration into grams/mol

.00503 M =.00503 mmol/1 mL
multiply (.00503 mmol/1mL)*(6.00 mL)= .0302 mmol => .00003016 mol enzyme

so molar mass = 2.02 g enzyme /.00003016 mol enzyme = 66976. 12732 g/mol , which is unusually enormous for a typical molar mass

I did the problem a few times and got the same answer. Althought it does seem high so I redid it a few times and kept getting the same answer. Maybe I'm missing something.

The answer looks right to me.

Benzoate said:
...so molar mass = 2.02 g enzyme /.00003016 mol enzyme = 66976. 12732 g/mol , which is unusually enormous for a typical molar mass

I assume that your answer is approximately 67,000 g/mol? This is 67 kilodaltons (kDa) which is well within the usual range for an enzyme.

i get the same, and expect big fat numbers for enzymes (as chemisttree points out)

4 to 1 :)

## What is molar mass?

Molar mass is the mass of one mole of a substance, expressed in grams per mole. It is a physical property that is commonly used in chemistry to determine the amount of a substance present in a given sample.

## How is molar mass calculated?

Molar mass is calculated by adding up the atomic masses of all the atoms in a molecule. The atomic mass of an element can be found on the periodic table.

## Why is molar mass important?

Molar mass is important because it allows us to convert between the mass of a substance and the number of moles present. It is also used in stoichiometric calculations to determine the amount of reactants needed and products formed in a chemical reaction.

## What units are used to express molar mass?

Molar mass is typically expressed in grams per mole (g/mol), but it can also be expressed in other units such as kilograms per mole (kg/mol) or milligrams per mole (mg/mol).

## How does molar mass differ from molecular weight?

Molar mass and molecular weight are often used interchangeably, but they are not exactly the same. Molar mass is the mass of one mole of a substance, while molecular weight is the average mass of one molecule of a substance. For elements and compounds made up of only one type of atom, molar mass and molecular weight are equal.

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