Question

Explain the Chlor-alkali process.

Answer 1

Hint: The chlor alkali method has been used in the United States, Western Europe, and Japan since the nineteenth century. During the twentieth century, it became the primary source of chlorine. The diaphragm cell and mercury cell processes have been in use for over a century and are both ecologically unfavourable due to the usage of asbestos and mercury, respectively, whereas the membrane cell process has only been around for 60 years. In terms of energy efficiency and the absence of hazardous substances, the membrane cell technique is better.

Complete answer:
The chlor alkali process is a commercial electrolysis method for sodium chloride solutions. It's the method for making chlorine and sodium hydroxide, both of which are industrially important compounds. In 1987, this operation produced 35 million tonnes of chlorine. In the chemical industry, the chlorine and sodium hydroxide generated in this method are frequently used. The procedure is usually carried out in a brine, which produces NaOH, hydrogen, and chlorine. When calcium chloride or potassium chloride is used instead of sodium, the products include calcium or potassium. Molten NaCl is used to produce chlorine and sodium metal, and condensed hydrogen chloride is used to produce hydrogen and chlorine. The process uses a lot of energy; for example, each tonne of sodium hydroxide produced, the process uses about 2500 kWh of electricity. Because the procedure produces the same quantity of chlorine and sodium hydroxide (two moles of sodium hydroxide per mole of chlorine), both products must be used in the same proportion. One mole of hydrogen is generated for every mole of chlorine produced. Much of the hydrogen is used to make hydrochloric acid, ammonia, and hydrogen peroxide, or it is burnt to generate electricity and/or steam.
$$2NaCl\left(aq\right)+2H_{2}O\left(l\right)\left(electrolysis\right)\to 2NaOH\left(aq\right)+C{l}_2\left(g\right)+H_2\left(g\right).$$

Note:
The anode (where the chlorine is generated) must be non-reactive due to the corrosive nature of chlorine generation, and has been manufactured from materials such as platinum metal, graphite (called plumbago in Faraday's day), or platinized titanium. Today's industry standard is a mixed metal oxide coated titanium anode (also known as a dimensionally stable anode). Platinum, magnetite, lead dioxide, manganese dioxide, and ferrosilicon (13-15 percent silicon) were all employed as anodes in the past.