How do halogens react with hydrogen?

Halogens react with hydrogen to form hydrogen halides, which are acidic and colourless gases.

Halogens are a group of five chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). When these elements react with hydrogen, they form hydrogen halides. For example, when hydrogen reacts with chlorine, it forms hydrogen chloride (HCl), a colourless and acidic gas. Similarly, hydrogen and bromine react to form hydrogen bromide (HBr), and hydrogen and iodine react to form hydrogen iodide (HI).

The reaction between hydrogen and halogens is a type of chemical reaction known as a combination or synthesis reaction. In this type of reaction, two or more simple substances combine to form a more complex substance. The general equation for the reaction between hydrogen and a halogen is H2 + X2 → 2HX, where X represents a halogen.

The reactivity of halogens decreases down the group, meaning fluorine is the most reactive and astatine is the least. Therefore, the reaction between hydrogen and fluorine is very vigorous and can occur spontaneously at room temperature, while the reaction between hydrogen and iodine requires a catalyst or higher temperatures to proceed.

Hydrogen halides are important chemicals in the industry. For example, hydrogen chloride is used in the production of chlorides and in the rubber industry, while hydrogen fluoride is used in the manufacture of fluorides and in the etching of glass.

In terms of safety, it's important to note that hydrogen halides are corrosive and can cause burns. They are also harmful if inhaled, so precautions should be taken when handling these substances.