The formation of a gas in a chemical reaction, due to ions changing places, often indicates that the reaction is which type?
a) synthesis

b) double-displacement

c) decomposition

d) single-displacement

The correct answer is D.

Explanation: In a chemical reaction, when there is changing of ions taking place and is leading to the formation of a gas can be considered as a single displacement reaction.

Single-Displacement reactions are defined as the reactions in which a higher reactive metal displaces a lower reactive metal. This is in reference to the reactivity series.

Hydrogen lies below in the reactivity series and when the higher reactive metal displaces hydrogen from a chemical reaction, it leads to the formation of hydrogen gas.

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