Question

Given: Mg\(^{2+}\)=5.68 meq/L, Na\(^{+}\)=9.90 meq/L, HCO\(_3^{-}\)=11.20 meq/L. \[ \frac{\text{HCO}_3^-}{\text{Ca}^{2+}}=2.8 \] Find Sodium Adsorption Ratio (SAR).

Hint:

SAR measures sodicity hazard—always use meq/L values.

Answer 1

Correct Answer: 4.5

Find Ca\(^{2+}\): \[ \frac{11.20}{\text{Ca}^{2+}} = 2.8 $\Rightarrow$ \text{Ca}^{2+} = 4.0\ \text{meq/L} \] SAR formula: \[ SAR = \frac{\text{Na}^+}{\sqrt{\frac{\text{Ca}^{2+} + \text{Mg}^{2+}}{2}}} \] Compute denominator: \[ \frac{4.0 + 5.68}{2} = 4.84, \sqrt{4.84} = 2.20 \] Thus: \[ SAR = \frac{9.90}{2.20} = 4.50 \] \[ \boxed{4.50} \]