Class 10 Salts, pH of salts , Chemicals from common salt , Products obtained from common salt

Topics to be covered

`=>` Salts
`=>` pH of salts
`=>` Chemicals from common salt
`=>` Products obtained from common salt


Salts are the ionic compounds that are produced after the neutralization reaction takes place between acid and base.

`color{green}(โ˜…)` `color{green}("๐…๐š๐ฆ๐ข๐ฅ๐ฒ ๐จ๐Ÿ ๐ฌ๐š๐ฅ๐ญ๐ฌ:")`

Salts having common acidic or basic radicals are said to belong to same family.

`color{green}(โ˜…)` ๐„๐ฑ๐š๐ฆ๐ฉ๐ฅ๐ž :

๐ฉ๐‡ ๐จ๐Ÿ ๐’๐š๐ฅ๐ญ๐ฌ

๐‚๐ก๐ž๐ฆ๐ข๐œ๐š๐ฅ๐ฌ ๐Ÿ๐ซ๐จ๐ฆ ๐‚๐จ๐ฆ๐ฆ๐จ๐ง ๐’๐š๐ฅ๐ญ

`color{green}(โ˜…)` Hydrochloric acid and sodium hydroxide combine to form sodium chloride (salt used in the food).

`color{green}(โ˜…)` `color{red}("๐‰๐”๐’๐“ ๐…๐Ž๐‘ ๐‚๐”๐‘๐ˆ๐Ž๐”๐’")`

Seawater contains many salts dissolved in it and from these salts Sodium chloride is separated . Deposits of solid salt are large crystals and are often brown due to impurities. This is called rock salt.

Beds of rock salt were formed when seas of bygone ages dried up. Rock salt is mined like coal.

`color{green}(โ˜…)` The common salt thus obtained is an important raw material for various materials of daily use, such as sodium hydroxide, baking soda, washing soda, bleaching powder and many more.

๐๐‘๐Ž๐ƒ๐”๐‚๐“๐’ ๐Ž๐๐“๐€๐ˆ๐๐„๐ƒ ๐…๐‘๐Ž๐Œ ๐‚๐Ž๐Œ๐Œ๐Ž๐ ๐’๐€๐‹๐“

`color{brown}(โ™ฃโ™ฃ)` `color{brown}("๐’๐จ๐๐ข๐ฎ๐ฆ ๐ก๐ฒ๐๐ซ๐จ๐ฑ๐ข๐๐ž")`

`color{green}(โ˜…)` `color{green}("๐๐ซ๐ž๐ฉ๐š๐ซ๐š๐ญ๐ข๐จ๐ง :")`

When electricity is passed through an aqueous solution of sodium chloride (called brine), it decomposes to form sodium hydroxide. The process is called the chlor-alkali process because of the products formedโ€“ chlor for chlorine and alkali for sodium hydroxide.

`color{red}(2NaCl (aq) + 2H_2O (l) โ†’ 2NaOH (aq) + Cl_2 (g) + H_2 (g))`

`color{green}(โ˜…)` `color{green}("๐๐ซ๐จ๐๐ฎ๐œ๐ญ๐ฌ:")`

Chlorine gas is given off at the anode, and hydrogen gas at the cathode. Sodium hydroxide solution is formed near the cathode.

`color{brown}(โ™ฃโ™ฃ)` `color{brown}("๐๐ฅ๐ž๐š๐œ๐ก๐ข๐ง๐  ๐ฉ๐จ๐ฐ๐๐ž๐ซ")`

`color{green}(โ˜…)` `color{green}("๐๐ซ๐ž๐ฉ๐š๐ซ๐š๐ญ๐ข๐จ๐ง:")`

Chlorine gas produced during the electrolysis of aqueous sodium chloride (brine) is used for the manufacture of bleaching powder. Bleaching powder `color{red}((CaOCl_2))` is produced by the action of chlorine on dry slaked lime `color{red}([Ca(OH)_2 ])`.

`color{red}(Ca(OH)_2 + Cl_2 โ†’ CaOCl_2 + H_2O)`

`color{green}(โ˜…)` `color{green}("๐”๐ฌ๐ž๐ฌ ๐จ๐Ÿ ๐›๐ฅ๐ž๐š๐œ๐ก๐ข๐ง๐  ๐ฉ๐จ๐ฐ๐๐ž๐ซ:")`

(i) for bleaching cotton and linen in the textile industry, for bleaching wood pulp in paper factories and for bleaching washed clothes in laundry.

(ii) as an oxidising agent in many chemical industries.

(iii) for disinfecting drinking water to make it free of germs.

`color{brown}(โ™ฃโ™ฃ)` `color{brown}("๐๐š๐ค๐ข๐ง๐  ๐ฌ๐จ๐๐š")`

Baking soda is commonly for making tasty crispy pakoras . Sometimes it is added for faster cooking. The chemical name of the compound is sodium hydrogencarbonate `color{red}((NaHCO_3 ))`. It is produced using sodium chloride as one of the raw materials.

`color{red}(NaCl + H_2O + CO_2 + NH_3 โ†’ underset("(Ammonium chloride)") (NH_4Cl) + underset("(Sodium hydrogencarbonate)")(NaHCO_3))`

`color{green}(โ˜…)` `color{green}("๐”๐ฌ๐ž๐ฌ ๐จ๐Ÿ ๐ฌ๐จ๐๐ข๐ฎ๐ฆ ๐ก๐ฒ๐๐ซ๐จ๐ ๐ž๐ง๐œ๐š๐ซ๐›๐จ๐ง๐š๐ญ๐ž" (NaHCO_3 ))` :

(i) For making baking powder, which is a mixture of baking soda (sodium hydrogencarbonate) and a mild edible acid such as tartaric acid.
When baking powder is heated or mixed in water, the following reaction takes place โ€“

`color{red}(underset("From any acid)")(NaHCO_3 + H^(+)) โ†’ CO_2 + H_2O + " Sodium salt of acid")`

Carbon dioxide produced during the reaction causes bread or cake to rise making them soft and spongy.

(ii) Sodium hydrogencarbonate is also an ingredient in antacids. Being alkaline, it neutralises excess acid in the stomach and provides relief.

(iii) It is also used in soda-acid fire extinguishers.

`color{brown}(โ™ฃโ™ฃ)` `color{brown}("๐–๐š๐ฌ๐ก๐ข๐ง๐  ๐ฌ๐จ๐๐š")`

Another chemical that can be obtained from sodium chloride is `color{red}(Na_2CO_3 .10H_2O)` (washing soda). Recrystallisation of sodium carbonate gives washing soda. It is also a basic salt.

`color{red}(underset("(Sodium carbonate )")(Na_2CO_3) +10 H_2O โ†’ Na_2CO_3 . 10 H_2O )`

`color{green}(โ˜…)` `color{green}("๐”๐ฌ๐ž๐ฌ ๐จ๐Ÿ ๐ฐ๐š๐ฌ๐ก๐ข๐ง๐  ๐ฌ๐จ๐๐š")`

(i) Sodium carbonate (washing soda) is used in glass, soap and paper industries.

(ii) It is used in the manufacture of sodium compounds such as borax.

(iii) Sodium carbonate can be used as a cleaning agent for domestic purposes.

(iv) It is used for removing permanent hardness of water.