SiO₂

CO₂

CaO

MgO

A scale measuring hydrogen ion concentration in a solution is called pH scale

The higher the hydrogen ion concentration in a solution, higher is its pH

We can measure pH generally from 0 to 14 on a pH scale

The 'p' in pH stands for 'potenz' in German meaning power

Half mole of nitrogen gas is measured 11·2 litre at STP

17 gram of ammonia gas contains 6·022 × 10²³ molecules at STP

22·4 litre of CO₂ gas at STP contains 44 gram of molecules

4 gram of hydrogen gas contains 6·022 × 10²³ molecules

A compound is a substance composed of two or more elements, chemically combined in a fixed proportion

Properties of a compound are different from its constituent elements

A compound is an impure substance

 The constituents of a compound can be separated only by chemical or electrochemical reactions