Science : Ch 01 – Chemical Reactions and Equations

Both these processes produce a cooling efect rather than heating. Dry ice absorbs heat from the environment to convert into gas. This feature makes it a good refrigerant. Processes of dilution of sulphuric acid and condensation of water vapours produce a large amount of heat. There fore these are exothermic processes.

The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is 2:1 by volume. In a decomposition reaction, a compound is broken down into its simpler forms. During electrolysis, water is broken down into oxygen gas and hydrogen gas due to the passage of electric current through it.

Inert gases like helium or nitrogen both can be used for the storage of fresh sample of oil for a long time, as they do not react with most elements, including oxygen

It is not atoms but the bonds between these atoms break and form during chemical reactions. Atoms of elements can rearrange but cannot change into other element.

The chemical reaction between dilute hydrochloric acid and granulated zinc is represented as follows:_x000D__x000D_Zn + 2HCl → ZnCl₂ + H₂↑

In Combination and Exothermic reaction, Calcium oxide (CaO), reacts vigorously with water to produce calcium hydroxide (slaked lime) and produces a large amount of heat. Since calcium oxide and water combine to form a single product, calcium hydroxide. So this is a combination reaction.

This is an example of two types of reaction: Redox reaction because oxidation (removal of hydrogen) and reduction (addition of hydrogen), both are happening simultaneously._x000D__x000D_Displacement reaction as it involves displacement by oxygen of H atoms from a compound (NH₃) with an other atom.

A double displacement reaction involves a displacement of two ions of two different compounds that results in the formation of new compounds. Here, only in reaction (ii), ions of both reactants are exchanged and two entirely different compounds are formed