Final answer:
The synthesis of ammonia demonstrates how temperature affects chemical reactions, altering thermodynamic spontaneity. Gas evolving reactions, like the reaction between nitric acid and sodium carbonate, exemplify chemical reactions that can change in temperature. Lastly, exothermic and endothermic processes are key examples of how heat exchange during chemical reactions can lead to temperature changes.
Step-by-step explanation:
Chemical reactions can be significantly affected by changes in temperature, which can alter the thermodynamic spontaneity of the reaction. A notable example of how temperature change affects chemical reactions is the synthesis of ammonia from nitrogen and hydrogen gas. Under normal conditions, this reaction is thermodynamically favorable but occurs slowly.
However, when the temperature is increased, it causes the -TΔS° term to dominate, making the reaction non-spontaneous at high temperatures, as indicated by an equilibrium constant (Keq) that is less than one. This demonstrates a typical conflict between thermodynamics and kinetics in real-world systems.
Another important aspect to consider is gas evolving reactions. For instance, when nitric acid reacts with sodium carbonate, it forms sodium nitrate, carbon dioxide, and water. This is a gas evolution reaction where carbon dioxide is the gas produced.
Matter can release or absorb heat during chemical reactions or physical changes. Reactions that release heat, such as the combustion reaction when using an oxyacetylene torch, are called exothermic processes. Conversely, reactions that absorb heat, such as the mixing of substances in a cold pack, are endothermic processes. Both these types of processes alter the temperature, which, in turn, can affect the rate and spontaneity of chemical reactions.