Which of the following formulas correctly represents the calculation of Residual Sodium Carbonate (RSC)?

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RSC = (CO3²⁻ + HCO3⁻) - (Na⁺ + K⁺ + Ca²⁺ + Mg²⁺)RSC = (CO3²⁻ + HCO3⁻) - (Ca²⁺ + Mg²⁺)RSC = (Na⁺ + K⁺) - (Ca²⁺ + Mg²⁺)RSC = (Ca²⁺ + Mg²⁺) - (CO3²⁻ + HCO3⁻)None of the above formulas are correct

Explanation

The Residual Sodium Carbonate (RSC) value is calculated using the concentrations of carbonate and bicarbonate ions minus the sum of calcium and magnesium ions. This is expressed as RSC = (CO3²⁻ + HCO3⁻) - (Ca²⁺ + Mg²⁺). This formula helps assess water suitability for irrigation by indicating the residual sodium hazard.