n an experiment, Ann mixes concentrated sulfuric acid with water in a reaction test tube. The walls of the test tube turn hot. What type of reaction has occurred?
It's an exothermic reaction, since heat is released.
The observation that the walls of the test tube turn hot suggests that an exothermic reaction has occurred. An exothermic reaction is a chemical reaction that releases energy in the form of heat. In this case, when concentrated sulfuric acid is mixed with water, it undergoes a highly exothermic reaction.
To further understand and confirm the type of reaction, it is important to consider the chemical equation for the reaction between sulfuric acid (H2SO4) and water (H2O):
H2SO4 + H2O → H3O+ + HSO4-
This equation indicates that sulfuric acid reacts with water to produce hydronium ions (H3O+) and hydrogen sulfate ions (HSO4-). The reaction is also known as a proton-transfer reaction, where one hydrogen ion is transferred from sulfuric acid (donating the proton) to water (accepting the proton).
The release of energy in the form of heat is a characteristic of exothermic reactions and is due to the breaking and forming of chemical bonds. In this case, the bonds between the hydrogen and oxygen atoms in sulfuric acid and water are broken, and new bonds are formed between sulfuric acid and the resulting hydronium and hydrogen sulfate ions. The energy released during these bond-breaking and bond-forming processes is responsible for the observed increase in temperature, causing the walls of the test tube to turn hot.