What are the chemicals obtained from common salt and how are they prepared
Salt is a chemical that is created when a metal is used to replace the acid's hydrogen. For instance, when Na is substituted for H in HCl, NaCl results. When an acid and a base react, salts are created. It is basically a neutralisation reaction that occurs when an acid and a base react. Salts are primarily solids, have high melting and boiling points, and conduct electricity when dissolved in water. All salts having the same positive ions are considered to belong to the same family of salts.
Table salt is made up of the elements sodium (Na) and chloride (Cl). Both elements are found linked together in nature as the compound sodium chloride rather than occurring independently and freely.
Common salt is made from seawater that has evaporated and is majorly extracted by the process of crystallisation of the brine solution.
Different Chemical Products Obtained from Common Salt
Common salt can serve as the raw material for the production of sodium hydroxide. Hydrogen gas and chlorine gas are the byproducts of the process. Baking soda or sodium hydrogen carbonate, washing soda or sodium carbonate decahydrate and bleaching powder or calcium hypochlorite can also be obtained as a product of common salt. Common salt can be used as a preservative for pickles and for preparing food. Common salt is employed in the production of soap and in the melting of ice.
How is Salt Obtained from Seawater?
Large-scale sources of sodium chloride include common salt that is made from seawater. To obtain the salt seawater is first trapped in big shallow pools and left to stand. The common salt is left behind as the water gets slowly evaporated into vapour under the heat of the sun.
The obtained common salt is then purified from its impurity by the process of crystallisation. Crystallisation is the process of purification of a compound from a concoction. For this, the substance is heated until it dissolves in a solvent or mixture of solvents. By letting some of the solvents evaporate, the mixture is concentrated. Crystals of the pure chemical are precipitated due to cooling the solvent. The final product is obtained by filtration followed by drying. Hence, salt is obtained from seawater by the process of evaporation and it is a physical change.
When the temperature rises, a liquid transforms into its gaseous state, which is known as evaporation. High energy molecules leave the liquid's surface during evaporation, which has a cooling effect. Sea and ocean water both contain significant amounts of salt. It is created when sodium and chlorine ions mix in water. This salt is frequently used for cooking and other purposes.
Rock salt is a common salt that has been extracted from subsurface sources. Rock salt is composed of huge crystals of common salt. Similar to coal, it is removed from an underground deposit.
Process of Obtaining Salt From Seawater
Alternative Process of Obtaining Salt from Seawater
Reverse osmosis is a method, in which the water is allowed to pass through a permeable filter eventually increasing the concentration of salt as the water is pushed out. This method is very expensive and can be used to separate salt for a few Litres of water only.
Another popular method is Electrodialysis. Water is poured into a big container in this process which involves adding a porous membrane between a negatively charged anode and a positively charged cathode. The anode then draws the positive sodium ions when the electric current is transferred, whereas the cathode attracts the negative chloride ions leaving water behind. As a result, salt and water are separated. Salt can also be obtained from sea water chemically. The seawater and decanoic acid are combined in a container, and the mixture is then heated. The solution is cooled after a while. The salt is formed during cooling and settles to the bottom of the container as precipitates. Decanoic acid and water combine to generate two layers that can be removed individually.
Interesting Facts
Salt, often known as sodium chloride (NaCl), has 60% chloride and 40% sodium by weight. Sodium, an essential mineral found in salt, serves as the body's main electrolyte.
Common salt is very important in our daily life because all signals to and from the brain, as well as those that travel within the cells, depend on sodium to function.
Key Features of Chemicals from Common Salt
Common salt has a lot of intriguing characteristics. It is white, transparent crystalline powder and colourless.
It is obtained from seawater by the process of evaporation which is a physical change.
The main sources of ocean salt are seafloor openings and rocks on land. The main source of salts dissolved in seawater is the rock on land. Due to its moderate acidity, rainwater that falls on land erodes rocks.
FAQs on Chemicals From Common Salt and Their Industrial Preparation
1. What are chemicals from common salt?
The main chemicals from common salt (NaCl) are sodium hydroxide (NaOH), chlorine (Cl2), hydrogen (H2), hydrochloric acid (HCl), bleaching powder (CaOCl2), and baking soda (NaHCO3). These chemicals are produced mainly from the electrolysis of brine (aqueous NaCl), called the chlor-alkali process.
- NaOH – used in soap and paper industries
- Cl2 – used for water purification and making PVC
- H2 – used as a fuel and in hydrogenation
- HCl – used in cleaning metals
- NaHCO3 – used in baking and fire extinguishers
2. What is the chlor-alkali process?
The chlor-alkali process is the electrolysis of brine (NaCl(aq)) to produce NaOH, Cl2, and H2. It is called chlor-alkali because it produces chlorine (chlor) and an alkali (NaOH).
- Electrolysis of aqueous NaCl is carried out.
- Chlorine gas is formed at the anode.
- Hydrogen gas is formed at the cathode.
- Sodium hydroxide remains in solution.
The overall balanced reaction is:
2NaCl(aq) + 2H2O(l) → 2NaOH(aq) + Cl2(g) + H2(g).
3. How is sodium hydroxide obtained from common salt?
Sodium hydroxide (NaOH) is obtained by the electrolysis of brine in the chlor-alkali process. When electricity is passed through concentrated NaCl solution, NaOH is formed in solution.
- Anode reaction: 2Cl-(aq) → Cl2(g) + 2e-
- Cathode reaction: 2H2O(l) + 2e- → H2(g) + 2OH-(aq)
- Na+ combines with OH- to form NaOH(aq)
The overall reaction is 2NaCl(aq) + 2H2O(l) → 2NaOH(aq) + Cl2(g) + H2(g).
4. What are the uses of sodium hydroxide (NaOH)?
Sodium hydroxide (NaOH), also called caustic soda, is widely used in industries and laboratories. It is a strong base produced from common salt.
- Manufacture of soaps and detergents
- Paper and pulp industry
- Textile processing
- Making bleach and cleaning agents
- Degreasing metals and petroleum refining
NaOH is highly corrosive and must be handled carefully.
5. How is chlorine gas prepared from common salt?
Chlorine gas (Cl2) is prepared from common salt by the electrolysis of brine, where chloride ions are oxidized at the anode. This is part of the chlor-alkali process.
- Anode reaction: 2Cl-(aq) → Cl2(g) + 2e-
- Chlorine is collected as a greenish-yellow gas.
Overall reaction:
2NaCl(aq) + 2H2O(l) → 2NaOH(aq) + Cl2(g) + H2(g).
6. What are the uses of chlorine gas?
Chlorine gas (Cl2) is mainly used as a disinfectant and in the manufacture of important chemicals. It is one of the key products obtained from common salt.
- Water purification and sewage treatment
- Manufacture of bleaching powder (CaOCl2)
- Production of hydrochloric acid (HCl)
- Making plastics like PVC (polyvinyl chloride)
- Preparation of pesticides and solvents
7. How is bleaching powder prepared from chlorine?
Bleaching powder (CaOCl2) is prepared by passing chlorine gas (Cl2) over dry slaked lime (Ca(OH)2). This reaction produces bleaching powder used for disinfecting water.
The balanced reaction is:
Cl2(g) + Ca(OH)2(s) → CaOCl2(s) + H2O(l).
- Used for bleaching cotton and linen
- Used in water purification
- Acts as an oxidizing agent
8. How is baking soda prepared from common salt?
Baking soda (sodium hydrogen carbonate, NaHCO3) is prepared from common salt by the Solvay process. In this process, brine reacts with ammonia and carbon dioxide.
The key reaction is:
NaCl(aq) + NH3(aq) + CO2(g) + H2O(l) → NaHCO3(s) + NH4Cl(aq).
- NaHCO3 precipitates out due to low solubility.
- Used in baking, antacids, and fire extinguishers.
9. How is washing soda obtained from baking soda?
Washing soda (sodium carbonate decahydrate, Na2CO3·10H2O) is obtained by heating baking soda (NaHCO3) and then crystallizing the product. Heating causes thermal decomposition.
Step 1: Thermal decomposition
2NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(g)
Step 2: Crystallization
Na2CO3(s) + 10H2O(l) → Na2CO3·10H2O(s)
- Used in cleaning and softening hard water
10. How is hydrochloric acid made from common salt?
Hydrochloric acid (HCl) is made by combining hydrogen gas (H2) and chlorine gas (Cl2), both obtained from the chlor-alkali process. The gases react to form hydrogen chloride, which dissolves in water to give HCl.
Reaction:
H2(g) + Cl2(g) → 2HCl(g)
- HCl(g) is dissolved in water to form aqueous HCl(aq).
- Used for cleaning metals and in chemical manufacturing.
