Final answer:
In the case of the Martian atmosphere, nitrogen is the solute, as it is one of the gases dissolved in the predominant carbon dioxide, which acts as the solvent.
Step-by-step explanation:
In the context of the Martian atmosphere, which comprises approximately 95% carbon dioxide, 3% nitrogen, and trace amounts of other gases, nitrogen would be termed the solute. In a solution, the solute is the substance that is dissolved in the solvent.
The solvent is the medium in which the solute is dissolved, and in the Martian atmosphere, carbon dioxide, being the most prevalent gas, would be considered the solvent. A solution refers to the homogenous mixture of two or more substances, which in this case is the atmospheric gases. The term concentration refers to the amount of solute in a given volume of solution, which would be the percentage of the gases other than carbon dioxide in the Martian atmosphere.