Question

An experimenter is testing different gasses for possible reactivity with each other by mixing them in a water-filled tube. For each observation listed below, select the statement that best describes whether or not it indicates a chemical reaction has taken place.

1) The total volume of gas increases by the volume of added gas. There are no other changes. No evidence of a reaction.
2) The total volume of gas decreases after the second gas is added. There are no other changes. Evidence of a reaction.
3) The total volume of gas increases by the volume of added gas, but the gas after mixing has a color that neither individual gas has. There are no other changes. Evidence of a reaction.
4) The total volume of gas increases by the volume of added gas. An acid-base indicator added to the water changes color where the gas is in contact with the water. The total volume of gas increases by less than the volume of added gas. There are no other changes.

Answer 1

A chemical reaction between gases can be identified through signs such as a decrease in total volume, color changes, and indicator color changes, all of which suggest that new substances have been formed.

Step-by-step explanation:

The observation and analysis of various signs can determine if a chemical reaction has occurred between different gases. For instance:

• If the total volume of gas increases by the volume of added gas with no other changes, this suggests there is no evidence of a chemical reaction.
• A decrease in the total volume of gas after adding the second gas, with no other changes, is indicative of a chemical reaction, as gases may have combined to form a new substance.
• The colour change of the gas mixture to a hue neither gas originally had, certainly implies a chemical reaction has taken place as new substances are likely formed.
• When an acid-base indicator changes color in contact with the gas, and if the total volume of gas increases by less than the added volume, it is a strong indicator of a chemical reaction, especially if a gas has been absorbed by the water due to the reaction.

Chemical reactions can also be identified by other observable changes such as temperature changes, light emission, bubble formation (gas production), and the formation of a solid product (precipitate).