An unknown substance turns methyl orange solution red. this shows that the substance

is acidic in nature

Explanation:

Acid base indicators are usually weak acids or weak bases. They change their color in the solution with change in the pH.

For any indicator say HIn , the dissociation can be shown as:

Methyl orange is one such indicator which shows red color in acidic medium and yellow color in basic medium.

Thus as the color of the methyl orange has turned red, the solution must be acidic in nature.

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

the answer for sodium is 0.186

the answer for rubidium is 0.251