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प्रश्न
On the basis of reactivity metals are grouped into three categories:
- Metals of low reactivity
- Metals of medium reactivity
- Metals of high reactivity
Therefore metals are extracted in pure form from their ores on the basis of their chemical properties.
Metals of high reactivity are extracted from their ores by electrolysis of the molten ore.
Metals of low reactivity are extracted from their sulphide ores, which are converted into their oxides. The oxides of these metals are reduced to metals by simple heating.
(a) Name the process of reduction used for a metal that gives vigorous reaction with air and water both.
(b) Carbon cannot be used as a reducing agent to obtain aluminium from its oxide? Why?
(c) Describe briefly the method to obtain mercury from cinnabar. Write the chemical equation for the reactions involved in the process.
OR
(c) Differentiate between roasting and calcination giving chemical equation for each.
उत्तर
(a) Metals towards the top of the reactivity series have a high level of reactivity. By heating with carbon, they cannot be extracted from their compounds. This is due to the fact that certain metals are more apt to bind oxygen than carbon. By using electrolytic reduction, these metals are produced. For instance, electrolysis of their molten chlorides yields sodium, magnesium, and calcium. While chlorine is released at the anode (the positively charged electrode), where the metals are deposited at the cathode (the negatively charged electrode).
\[\ce{2HgS(s) + 3O_2(g)->[Heat] 2HgO(s) + 2SO_2(g)}\]
\[\ce{2HgO(s)->[Heat]2Hg(l) + O_2(g)}\]
OR
(c) Difference between roasting and calcination are:
Calcination: Calcination is the process of converting a concentrated ore into its oxide by heating it below its melting point without the presence of air. It often applies to ores of hydroxide and carbonate.
Example: \[\ce{MgCO_3->[\Delta] MgO+CO_2}\]
In this process, magnesium carbonate is heated without the presence of air to produce magnesium oxide.
Roasting: Roasting is the name for the metallurgical procedure in which an ore is heated over its melting point in the presence of extra air to produce its oxide. Sulphur is typically emitted as sulphur dioxide, a gas, after being transformed from a sulphide to an oxide.
Example: \[\ce{2ZnS + 3O_2->[\Delta]2ZnO + 2SO_2}\]
In this process, zinc sulphide is changed into zinc oxide and sulphur is liberated as the gas sulphur dioxide.
संबंधित प्रश्न
Name the most abundant metal in the earth's crust.
Fill in the following blank with suitable word:
Bronze is an alloy of copper and .........
Explain giving one example, how highly reactive metals (which are high up in the reactivity series) are extracted.
Name the following:
Name two metals always find in combined state.
choose the most appropriate term to match the given description.
Heating of the ore in the absence of air to high temperature
Zinc blende is converted to oxide by ______ process.
Write the name.
Metals which are amphoteric in nature.
Explain the following reaction with the balanced equation.
Chlorine dissolved in water
Explain in brief types of extraction of less reactive metals according to their reactivity.
Answer the questions on the following passage.
The minerals from which the metal can be separated economically are called ores. Ores contain many types of impurities such as soil, sand and rocky substances along with metal compounds. These impurities are called gangue.
Metals can be extracted from their ores by means of various methods of separation. The process of extraction of metal in a pure state from the ores is also a part of metallurgy.
Ores are taken out from the mines and the gangue is usually separated from the ore at the site itself by various methods. Then the ores are carried out to the place where metals are produced. Here metals are extracted in pure form. Then metals are further purified by different methods of purification. This entire process is called metallurgy. Most metals being reactive do not occur in nature in the free state but are found in combined state as their salts such as oxides, carbonates, sulphides, and nitrates. however, the most unreactive metals that are not affected by air, water and other natural factors like silver, gold, platinum, generally occur in a free state. The compounds of metals that occur in nature along with the impurities are called minerals.
- What are ores?
- Which processes are involved in the branch of metallurgy? What is metallurgy?
- Which metals are found in a free state?
- In what forms are metals found in combined state?
- What is gangue?
