Ans. Atom.

## Q2. How many ions are present in one mole of ions?

Ans. 6.022 x $${10}^{23}$$.

## Q3. Write the names of symbols of elements where the symbols are taken from their names in English.

Ans. The symbols of the following elements have been taken from their names in English: Calcium (Ca), oxygen (0), zinc (Zn), magnesium (Mg) etc.

## Q4. What is an atom according to Dalton’s atomic theory?

Ans. According to Dalton’s atomic theory, an atom is the ultimate particle of matter which cannot be further divided into anything simpler than itself.

## Q5. Carbon dioxide, collected from different sources contains carbon and oxygen in the same proportion. Which law of chemical combination governs this?

Ans. This is governed by law of constant proportions.

## Baking soda, washing soda, blue vitriol, green vitriol, gypsum, oil of vitriol or white vitriol, soda ash, marble, lime water

Ans.

 Common name Chemical name Chemical formula Baking soda Sodium bicarbonate $$NaHC{ O }_{ 3 }$$ Washing soda Sodium carbonate $$N{ a }_{ 2 }C{ O }_{ 3 }.10{ H }_{ 2 }O$$ Blue vitriol Copper sulphate $$CuS{ O }_{ 4 }.5{ H }_{ 2 }O$$ Green vitriol Ferrous sulphate $$FeS{ O }_{ 4 }.7{ H }_{ 2 }O$$ Gypsum Calcium sulphate $$CaS{ O }_{ 4 }.2{ H }_{ 2 }O$$ Oil of vitriol Sulphuric acid $${ H }_{ 2 }S{ O }_{ 4 }$$ Soda ash Sodium carbonate $$N{ a }_{ 2 }C{ O }_{ 3 }$$ Marble Calcium carbonate $$CaC{ O }_{ 3 }$$ Lime water Calcium hydroxide $$Ca({ OH) }_{ 2 }$$