A 1.336-g sample of commercial contaminated by was dissolved in water, and the resulting solution was diluted to 500.0 mL. A 50.00-mL aliquot of this solution was treated with 40.00 mL of 0.05304 M and boiled to remove . The excess acid consumed 4.97 mL of 0.04809 M (phenolphthalein indicator). An excess of neutral was added to another 50.00-mL aliquot to precipitate the carbonate as . The solution was then titrated with 28.56 mL of the acid to a phenolphthalein end point. Calculate the percentage , , and in the sample, assuming that these are the only compounds present.

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e

a polar bond is formed when electrons are shared unevenly between atoms