What do you obtain when you combine an acid with an alkali?

When an acid is combined with an alkali, the reaction is known as neutralization. In this process, the hydrogen ions (H⁺) from the acid react with the hydroxide ions (OH⁻) from the alkali to form water (H₂O). Simultaneously, the remaining ions from the acid and alkali combine to form a salt. This can be generalized by the equation:

Acid + Alkali → Salt + Water

The formation of salt and water is a fundamental aspect of acid-base chemistry and is crucial in understanding many chemical reactions and processes in both laboratory and practical applications. The other options do not accurately represent the products formed in an acid-alkali reaction. For example, combining an acid with a metal typically results in the production of hydrogen gas and a salt, while carbon dioxide and water are products of a reaction between an acid and a carbonate, rather than an alkali.