I'm having trouble turning mM to mOsmoles. The equation goes like this: red blood cell are placed into a beaker filled with .5L of a 150mM NACL solution. NACL is non-penetrating solute and will not cross the red blood cell membrane.

Question

I'm having trouble turning mM to mOsmoles. The equation goes like this: red blood cell are placed into a beaker filled with .5L of a 150mM NACL solution. NACL is non-penetrating solute and will not cross the red blood cell membrane.

I have 150mM/0.5L * 2mOsM/100mM

But something isn't adding up since I have to compare it to a red blood cell equal to 300mOm. I keep getting 6000mOsM

Answer 1

To convert millimoles (mM) to milliosmoles (mOsm), you need to consider the osmotic properties of the solute in question. In this case, you have sodium chloride (NaCl), which is a non-penetrating solute that does not cross the red blood cell membrane.

The key fact to remember is that 1 mM of a non-penetrating solute is equal to 2 milliosmoles (mOsm). Therefore, you can use this conversion factor to calculate the osmolality:

150 mM NaCl * 2 mOsm/1 mM NaCl = 300 mOsm

So, the 150 mM NaCl solution has an osmolality of 300 mOsm.

In order to compare this value to the red blood cell osmolality of 300 mOsm, you can see that they are equal. Therefore, the osmolality of the solution matches the osmolality of the red blood cell.

It seems like there might be an error in your calculations when you multiply 150 mM by 2 mOsm/100 mM. The correct conversion factor to use is 2 mOsm/1 mM as explained earlier.

Answer 2

To convert from millimoles (mM) to milliosmoles (mOsm), you need to consider the osmolarity of the solute.

In this case, you have a 150 mM NaCl solution. First, divide the concentration by 1000 to convert mM to moles:

150 mM NaCl = 150/1000 = 0.15 moles NaCl

Next, multiply the number of moles by the Van't Hoff factor (i) for NaCl, which is 2 because it dissociates into two ions in water:

0.15 moles NaCl * 2 = 0.3 osmoles NaCl

Now, calculate the osmolarity by dividing the number of osmoles by the volume of the solution:

0.3 osmoles NaCl / 0.5 L = 0.6 osm/L or 600 mOsm

So, the osmolarity of the NaCl solution is 600 mOsm.

Now, to compare it to a red blood cell equal to 300 mOsm, simply subtract the osmolarity of the solution from the osmolarity of the red blood cell:

300 mOsm - 600 mOsm = -300 mOsm

The result is negative because the red blood cell has a lower osmolarity compared to the NaCl solution.