[1234567899]

What would the chemical equation/equations for the reaction in the following experiment be? And what is happening to cause the pH increase?

Solution A
•   Dissolve 0.37 g of sodium thiosulfate in 200 mL of water in a beaker.
•   Dissolve 9 g of potassium iodide in a separate 200 mL of water in a beaker.
•   Combine these solutions in the volumetric flask.
•   Add 4 mL of 0.1M ethanoic acid, then add water to adjust the total volume to 500 mL.
Solution B
•   Measure 100 mL of solution A into a 250 mL beaker and mix in 3 drops of universal indicator.
•   Freshly prepare 0.056M of hydrogen peroxide by diluting 7 mL of 6% hydrogen peroxide solution with 250 mL of water.

1.   In a beaker, mix 100 mL of solution A with 30 mL of solution B.
2.   Start the stopwatch from the time that solution A and B are combined, to the time at which the colour transitions from red, orange, yellow, etc... to a dark purple.

[chenbeier]

What are your own ideas. Read forum rules.  What is unclear.