Answer :
Final answer:
To find the milliequivalents of sodium in 250 mL of a solution of sodium bicarbonate that is isoosmotic with plasma (300 mOsm/L), we multiply the osmolarity by the volume (300 mOsm/L × 0.25 L), which equals 75 mOsm. Since 1 mOsm of NaHCO3 yields 1 meq of Na+, the answer is (b) 75 meq.
Explanation:
The question is asking us to calculate the amount of sodium (in milliequivalents, meq) contained in 250 mL of a sodium bicarbonate (NaHCO3) solution that is isoosmotic with plasma, which has an osmolarity of 300 milliosmoles per liter (mOsm/L).
To calculate this, we need to know the osmolarity of the NaHCO3 solution and use this to find the equivalent amount of sodium.
Since the solution is isoosmotic with plasma, we assume it also has an osmolarity of 300 mOsm/L. Sodium bicarbonate dissociates into sodium (Na+) and bicarbonate (HCO3-) ions, contributing 1 Na+ per NaHCO3 molecule. Therefore, each milliosmole of NaHCO3 contributes 1 meq of Na+, because 1 meq of Na+ is equivalent to 1 mmol of Na+.
Given the volume (250 mL or 0.25 L) and osmolarity (300 mOsm/L), we can calculate the total milliequivalents of sodium as follows:
300 mOsm/L × 0.25 L = 75 mOsm
Since we have established that 1 mOsm of NaHCO3 yields 1 meq of Na+, the total amount of sodium in meq is also 75 meq. Therefore, the correct answer is (b) 75 meq.
