CHEMISTRY · Multi-part · AP · Chemistry · Chemical Reactions · Chemical Reactions
Problem
In wastewater treatment, excess sulfite ions can be oxidized by hypochlorite ions under basic conditions to produce sulfate ions and chloride ions.
Unbalanced skeletal equation (basic solution):
SO32−+OCl−→SO42−+Cl−
A treatment plant has a 0.150 M solution of Na2SO3 (aq). The engineers plan to add commercial bleach that is 5.0 % NaOCl by mass (density of the bleach solution = 1.06gmL−1) to ensure complete reaction.
(a) Balance the redox reaction above in basic solution, providing the full set of coefficients (including any required OH− or H2O species) in the simplest whole-number ratio.
(b) Using your balanced equation from part (a), determine the mole ratio of hypochlorite ions consumed per sulfite ion consumed.
(c) A 250 mL sample of the 0.150 M Na2SO3 solution is to be treated. Calculate the mass (in grams) of pure NaOCl required for complete reaction with this sample.
(d) Using the concentration and density data provided for the commercial bleach, calculate the minimum volume (in milliliters) of the bleach solution that must be added to supply the mass of NaOCl determined in part (c). Report the answer to the correct number of significant figures.