I know this is easy but it's been a while for me.
Calculate the osmolarity of the following:
-25mM CaCl2
-100mg/dl Glucose
-0.20 M MgSo4 which is 50% dissociated
Thank you!!!
To calculate the osmolarity of a solution, you need to consider the number of particles in the solution (the solute) and their concentration. The osmolarity is expressed in osmoles per liter (osmol/L) or milliosmoles per liter (mosmol/L).
Let's tackle each component of the solution separately:
1. CaCl2:
This compound dissociates into three ions in solution: one calcium ion (Ca2+) and two chloride ions (Cl-). Since it's given as 25 mM (millimolar), we can directly use this value as the concentration, which is 25 millimoles per liter (mmol/L).
2. Glucose:
Glucose does not dissociate into ions in solution, so we consider it as a non-dissociating solute. The concentration is given as 100 mg/dL (milligrams per deciliter), which is 100 milligrams per 100 milliliters (mg/100mL). To convert this concentration to millimoles per liter, we need to do a conversion to moles and adjust for the volume:
100 mg/100 mL = 1 g/L (since 1 g = 1000 mg)
1 g/L / 180.16 g/mol (molar mass of glucose) = 5.55 mmol/L
3. MgSO4:
This compound dissociates into three ions in solution: one magnesium ion (Mg2+) and two sulfate ions (SO42-). However, it's stated that it's 50% dissociated. This means only half of the compound forms ions, while the other half remains as undissociated MgSO4. Therefore, we need to calculate the concentration of both the dissociated ions and the undissociated compound.
- Dissociated ions (Mg2+ and SO42-):
The concentration is given as 0.20 M (molar), which is 0.20 moles per liter (mol/L). Since it's 50% dissociated, we only consider half of this concentration: 0.10 mol/L.
- Undissociated compound (MgSO4):
The concentration is also given as 0.20 M (molar), but since it's not dissociated, we consider the entire concentration: 0.20 mol/L.
Now, let's calculate the osmolarity by summing the contributions from each component:
Osmolarity = (CaCl2 concentration) + (Glucose concentration) + (Mg2+ and SO42- concentration) + (undissociated MgSO4 concentration)
Osmolarity = (25 mmol/L) + (5.55 mmol/L) + (0.10 mol/L) + (0.20 mol/L)
Osmolarity = 30.55 mmol/L + 0.10 mol/L + 0.20 mol/L
Now, we need to convert the moles to millimoles, so:
Osmolarity = 30550 µmol/L + 100 µmol/L + 200 µmol/L
Osmolarity = 30850 µmol/L
Finally, we convert the micromoles to milliosmoles:
Osmolarity = 30850 mosmol/L
Therefore, the osmolarity of the given solution is 30850 milliosmoles per liter (mosmol/L).