Important Chemical Equations

📝 Important Chemical Equations 

Chapter 1 (Chemical Reactions and Equations) 

➤ We should know something about the various oxides of iron metals. Iron (Fe) forms two main oxides. 

(i) Iron (II) oxides, `FeO`, this is called iron (II) oxide because the valency of iron in it is two. The common name of iron (II) oxides is ferrous oxide. 

(ii) Iron (III) oxide, `Fe_2O_3`, this is called iron (III) oxide because the valency of iron in it is three. the common name of iron (III) oxide is ferric oxide. 

`Fe_3O_4` is a mixture of iron (II) oxide, `FeO`, and iron (III) oxide, `Fe_2O_3`. So `Fe_3O_4` is named as iron (II, III) oxide. The common name of `Fe_3O_4` is magnetic iron oxide. 

➤ Burning of a magnesium ribbon in air and collection of magnesium oxide in a watch-glass. Magnesium ribbon burns with a dazzling white flame and changes into a white powder.

`2Mg (s) + O_2 (g) overset{triangle}{rightarrow} 2MgO (s)`     

➤ The chemical reaction between lead nitrate and potassium iodide gives lead iodide (yellow ppt., insoluble in water.) and potassium nitrate. 

`Pb(NO_3)_2 (aq) + 2KI (aq) rightarrow  PbI_2 (s) + 2KNO_3 (aq)`

➤ Formation of hydrogen gas by the action of dilute sulphuric acid on zinc

`Zn (s) + H_2SO_4 (aq) rightarrow ZnSO_4 (aq) + H_2 (g) uparrow + triangle`

➤ Another reaction of zinc with  dilute hydrochloric acid 

`Zn (s) + 2HCl (aq) rightarrow ZnCl_2 (aq) + H_2 (g) uparrow + triangle`

➤ Iron reacts with steam gives iron oxide and evolve hydrogen gas 

`3Fe (s) + 4H_2O (g) rightarrow Fe_3O_4 (s) + 4H_2 (g)`

➤Carbon monoxide gas reacts with hydrogen, produce methanol (methyl alcohol or methyl hydrate).

`CO (g) + 2H_2 (g) overset{340  atm, 300^° C}{rightarrow} CH_3OH (l)`

➤ Photosynthesis

➤ Hydrogen gas reacts with chlorine gas to produce hydrogen chloride gas. 

`H_2 (g) + Cl_2 (g) rightarrow 2HCl (g)`

➤ Calcium oxide (quick lime) reacts vigorously with water to produce slaked lime (calcium hydroxide) releasing a large amount of heat. 

`CaO (s) + H_2O (l) rightarrow Ca(OH)_2 (aq) + triangle`

➤ Slaked lime is used for whitewashing walls. Calcium hydroxide reacts slowly with the carbon dioxide in the air to form a thin layer of calcium carbonate on the walls. Calcium carbonate (white ppt.) is formed after two to three days of whitewashing and gives a shiny finish to the walls.

`Ca(OH)_2 (aq) + CO_2 (g) rightarrow CaCO_3 (s) + H_2O (l)`

➤ Burning of coal

`C (s) + O_2 (g) rightarrow CO_2 (g)`

➤ Formation of water from `H_2(g)` and `O_2(g)`

`2H_2 (g) + O_2 (g) rightarrow 2H_2O (l)`

➤ Burning of natural gas

`CH_4 (g) + 2O_2 (g) rightarrow CO_2 (g) + 2H_2O (g)`

➤ Respiration 

`C_6H_12O_6 (aq) + 6O_2 (aq) rightarrow  6CO_2 (aq) + 6H_2O (l) +` energy

Thermal Decompotion Reactions

➤ Green-coloured ferrous sulphate crystals or ferrous sulphate heptahydrate (`FeSO_4. 7H_2O)` lose water when heated and the colour of the crystals changes (white). Anhydrous ferrous sulphate `(FeSO_4)` then decomposes to ferric oxide `(Fe_2O_3)`, brown in colour, sulphur dioxide `(SO_2)` and sulphur trioxide `(SO_3)`. Ferric oxide is a solid, while `SO_2` and `SO_3` are gases. A smell of burning sulphur is obtained due to the formation of sulphur dioxide. 

`2FeSO_4 (s) overset{triangle}{rightarrow} Fe_2O_3 (s) + SO_2 (g) + SO_3 (g)`

➤ Decomposition of calcium carbonate to calcium oxide and carbon dioxide on heating is an important decomposition reaction

`CaCO_3 (s) overset{Delta}{rightarrow} CaO (s) + CO_2 (g)` 

More equations will be updated soon