Acatalyst is: a. a solid product of a reaction. b. one of the reactants in a single-replacement reaction. c. not used up in a reaction. d. the product of a combustion reaction.

A catalyst is C. not used up in a reaction.

Explanation:

A catalyst is a substance capable of promoting or accelerating a chemical reaction without directly intervening in it. That is to say that at the end of the reaction the catalyst remains unchanged. Therefore, it is not considered as a reagent or product according to the stoichiometry of the reaction.

Catalysts that are responsible for increasing the speed of a chemical reaction are called positive catalysts and are the most common and used. But there are also  negative catalysts, also known as inhibitory catalysts. These reduce the speed of a reaction.

Catalysts can be classified into:

Homogeneous: this catalyst is dissolved with those reagents that are in the same phase. Electrocatalyst: is that used to improve the speed of semi-reaction of batteries that work as fuel. Heterogeneous: also known as contact, it is characterized by not being in the same stage as the reagents. Biological: also known as enzyme, they are proteins whose main function is to accelerate the speed in biochemical reactions.

Finally, the correct answer is a catalyst is not used up in a reaction.

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The atomic nucleus made up from protons (yellow) and neutrons (blue) and held together by nuclear forces. nuclear forces (also known as nuclear interactions or strong forces) are the forces that act between two or more nucleons. they bind protons and neutrons (“nucleons”) into atomic