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Calculations determining MSO₂/FSO₂ concentrations at different pH values

Relationship between molecular SO₂, FSO₂ and pH

Molecular SO₂ ppm = FSO₂ ppm * 10^{1.77 - pH}

This is derived from -

SO2

+

H2O

< == >

HSO3-

+

H+





				[HSO3 - ] [H + ]
K		=		----------------				( K = 10 - 1.77)
				[SO2]





		[HSO3 - ] [H + ]
[SO2]	=	----------------
		K





		[HSO3 - ] [H + ]
[SO2]	=	----------------
		10 - 1.77





Since

pH

=

- log10 [H +]

(i.e. If [H +] = 10 - 3.33 M , then pH = 3.3 )





Then	[H +]	=	10 - pH





				10 - pH		*		[HSO3 - ]
[SO2]		=		-------	--------	------	-	---------
					10 - 1.77





	[SO 2]	=	10 - pH	*	[HSO3 - ]	*	10 1.77





	Molecular SO 2	ppm	=	FSO2	ppm	*	10 1.77 - pH	(since FSO2 approximates for [HSO3 - ] )