Sodium content of one liter of isotonic saline is:
## **Core Concept**
Isotonic saline, also known as 0.9% saline solution, is a solution that has the same osmolarity as blood. It is commonly used in medical settings for fluid resuscitation and as a vehicle for medication administration. The osmolarity of isotonic saline is 308 mOsm/L.
## **Why the Correct Answer is Right**
The correct answer is . To understand why, let's calculate the sodium content in one liter of isotonic saline. Isotonic saline is 0.9% sodium chloride (NaCl) solution. The molecular weight of NaCl is approximately 58.44 g/mol. A 0.9% solution means there are 9 grams of NaCl per liter of solution.
The molar concentration of NaCl in isotonic saline can be calculated as follows:
[ text{Molarity of NaCl} = frac{9 , text{g/L}}{58.44 , text{g/mol}} approx 0.154 , text{mol/L} ]
Since NaCl dissociates into two ions (Na+ and Cl-), the osmolarity contributed by NaCl is twice its molarity, but for calculating sodium content, we focus on the sodium ion (Na+). Therefore, the concentration of sodium ions (Na+) from NaCl is 0.154 mol/L.
The molar mass of sodium (Na) is approximately 22.99 g/mol.
[ text{Sodium content} = 0.154 , text{mol/L} times 22.99 , text{g/mol} approx 3.54 , text{g/L} ]
## **Why Each Wrong Option is Incorrect**
- **Option A:** This option suggests a sodium content that is too low compared to the calculated value of approximately 3.54 g/L.
- **Option B:** This is the correct answer, as calculated above.
- **Option C:** This option suggests a higher sodium content than calculated.
- **Option D:** This option also suggests a sodium content that does not match the calculated value.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that isotonic saline has a sodium concentration close to that of human blood, which makes it suitable for intravenous administration without causing significant shifts in electrolyte balance. The sodium content in isotonic saline is approximately 154 mEq/L, which is close to the physiological concentration of sodium in human blood.
## **Correct Answer:** . 154 mEq/L.