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प्रश्न
Observe the following diagram and write answers.
- Name the method.
- Write anode reaction and cathode reaction.
- Why fluorspar and cryolite are added in the mixture?
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उत्तर
- This method is electrolytic reduction of alumina.
- Anode reaction:
\[\ce{2O^{2-} -> O2 + 4e^-}\] (Oxidation)
Cathode reaction:
\[\ce{Al^{3+} + 3e^- -> Al_{(l)}}\] (Reduction) - Alumina has a very high melting point (>2000 °C). The purpose of mixing ‘cryolite’ and ‘fluorspar’ with ‘alumina’ in the electrolytic reduction of alumina is to carry out the process at a much lower temperature. Addition of cryolite and fluorspar reduces the melting point of alumina to about 1000 °C.
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संबंधित प्रश्न
Metallic oxides of zinc, magnesium and copper were heated with the following metals.
| Metal | Zinc | Magnesium | Copper |
| Zinc oxide | – | – | – |
| Magnesium oxide | – | – | – |
| Copper oxide | – | – | – |
In which cases will you find displacement reactions taking place?
Write the steps involved in the extraction of pure metals in the middle of the activity series from their carbonate ores.
Name the most abundant metal in the earth’s crust.
Why does a new aluminium vessel lose shine so soon after use?
Name two metals which occur in nature in free state as well as in combined state.
Name the metal which is extracted from haematite ore.
Which metal can be extracted from the following ore?
bauxite
Aluminum is used in thermite welding:
what is thermit?
Name the anode, the cathode and the electrolyte used in the electrolytic refining of impure copper.
An element has its electron configuration as 2,8,8,2. Now answer the following questions.
a) What is the atomic number of this element?
b) What is the group of this element?
c) To which period does this element belong?
How an ore is concentrated by froth floatation process?
Complete the incomplete statement with missing word:
Non-metals form acidic oxides while metals form ______.
Name a non- metal that has a metallic luster and sublimes on heating.
Define calcination.
Iron is _______.
Write the name.
Strongly heating carbonate ores in insufficient air -
Write the molecular formulae of the following compound.
Cryolite
Explain the following reaction with the balanced equation.
Dry aluminium hydroxide is ignited at 1000 °C
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?
Which of the following metals exist in their native state in nature?
(i) Cu
(ii) Au
(iii) Zn
(iv) Ag
