Subtopic: Irrigation and drainage water quality and reuse
Question Statement:
An irrigation water sample contains $\text{Na}^+ = 12.0\text{ meq/L}$, $\text{Ca}^{2+} = 5.0\text{ meq/L}$, and $\text{Mg}^{2+} = 3.0\text{ meq/L}$. The Sodium Adsorption Ratio ($SAR$) of the water is ________ (answer in integer).
Answer Key:
6
Step-by-Step Solution & Explanation
The formula for Sodium Adsorption Ratio ($SAR$) is:
$SAR = \frac{[\text{Na}^+]}{\sqrt{\frac{[\text{Ca}^{2+}] + [\text{Mg}^{2+}]}{2}}}$
Given ionic concentrations in $\text{meq/L}$:
• $[\text{Na}^+] = 12.0$
• $[\text{Ca}^{2+}] = 5.0$
• $[\text{Mg}^{2+}] = 3.0$
$\frac{5.0 + 3.0}{2} = \frac{8.0}{2} = 4.0$
$\sqrt{4.0} = 2.0$
$SAR = \frac{12.0}{2.0} = 6.0$