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1) For sulfurous acid (H 2 SO 3 , a diprotic acid), write the equilibrium dissoc

ID: 636137 • Letter: 1

Question

1) For sulfurous acid (H2SO3, a diprotic acid), write the equilibrium dissociation reactions and the corresponding expressions for the equilibrium constants, Ka1and Ka2.

2) Write the balanced neutralization reaction for sulfurous acid reacting with sodium hydroxide.

DATA ANALYSIS 1. (Part I) Use the calibration equation from Item 1 and the absorbance reading for your unknown solution to determine [SCN-] (Part II) Compare your experimental [SCN-11, of your unknown, with the actual [SCN", suggest reasons for the disparity. 2.

Explanation / Answer

1)

For the Ka1 reaction

H2SO3 ============== H+ + HSO3-

Ka = [Products]/[Reactants] = [H+][HSO3-]/[H2SO3]

For the Ka2 reaction

HSO3- ============== H+ + SO3(2-)

Ka2 = [Products]/[Reactants] = [H+][SO3(2-)]/[HSO3-]

2)

The balanced reaction will be

2NaOH + H2SO3 ------------ Na2SO3 + 2H2O