What mass of sodium arsenate would be present?

Science
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If this arsenic is present as arsenate, AsO3−4, what mass of sodium arsenate would be present in a 1.80L

 sample of drinking water that just meets the standard? Parts per billion is defined on a mass basis

Jan 18th, 2015

The problem this causes in in determining the mass-to-mass ratio (the gravimetric ratio) between the salt and the elemental forms of As. 
I'll use Na2HAsO4.7H2O in the calculation, but you can follow the same procedure with any of the salt formulae. 
1 mole of Na2HAsO4.7H2O: contains 1 mole of As 
Set up the gravimetric factor using this molar relationship. 
(1 mole of Na2HAsO4.7H2O)/(1 mole of As) = ((1 mole of Na2HAsO4.7H2O)*(312.01 g/mol))/((1 mole of As)*(74.92 g/mol)) = (312.01 g Na2HAsO4.7H2O)/(74.92 g As) = (4.16 g Na2HAsO4.7H2O)/(1 g As)

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Jan 18th, 2015

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Jan 18th, 2015
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Jan 18th, 2015
Dec 9th, 2016
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