The best answer is answer b.
A chemical reaction has taken place,
as indicated by the change in temperatures and color, as well as the production
of a gas which inflated the bag.
25. Which of the following statements could Jessie reasonably
infer from the results so far?
a) A physical change has taken place. Water must have changed
to a gas which inflated the bag.
b) A chemical reaction has taken place. The bag inflation indicates
a gas has been produced.
c) Production of heat requires all of these chemicals to be
mixed together.
d) The color change is caused by the white chemicals (NAHCO3
and CaCls) diluting the red color of the phenol red solution.
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Slichter