Chemistry - Acids, Alkalis, and the pH Scale

Acids are substances that release hydrogen ions ($H^+$) when dissolved in water. They have a $pH$ less than 7.

Alkalis are bases that are soluble in water and release hydroxide ions ($OH^-$). They have a $pH$ greater than 7.

The $pH$ scale ranges from 0 to 14, where 7 is neutral (e.g., pure $H_2O$). Strong acids have $pH$ 0-3, while strong alkalis have $pH$ 11-14.

Indicators are chemicals that change color depending on $pH$. Common ones include Litmus (Red in acid, Blue in alkali), Methyl Orange (Red in acid, Yellow in alkali), and Phenolphthalein (Colorless in acid, Pink in alkali).

Neutralization is a chemical reaction where an acid and a base react to form a salt and water. The ionic equation is $H^+_{(aq)} + OH^-_{(aq)} ightarrow H_2O_{(l)}$.

Acids react with metals to produce a salt and hydrogen gas ($H_2$). The presence of $H_2$ is confirmed by the 'squeaky pop' test.

Acids react with metal carbonates to produce a salt, water ($H_2O$), and carbon dioxide ($CO_2$). $CO_2$ is tested by bubbling it through limewater, which turns cloudy.