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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 two metals which are always found in combined state.
What is passive iron?
Name:
The allotrope of the non-metal carbon which conducts electricity.
X is an element in the form of a powder. X burns in oxygen and the product is soluble in water. The solution is tested with litmus. Write down only the word which will correctly complete each of the following sentences:
(a) If X is a metal, then the litmus will turn ______.
(b) If X is a non-metal, then the litmus will turn ______.
(c) If X is a reactive metal, then ______ will be evolved, when X reacts with dilute sulphuric acid.
(d) If X is a non -metal, it will form _ oxide, which will form ______ solution with water.
(e) If X is a non -metal, it will not conduct electricity unless it is carbon in the form of ______.
State three objectives achieved during the roasting of ores.
Usually ______ ores are subjected to ______ which is done in the absence of air.
If Cu, Fe, Zn, Al elements are arranged in increasing order of their reactivity then the correct order would be which of the following?
Explain concept with example/explain with the help of a balanced equation.
Roasting
Which of the statements about the reaction, \[\ce{ZnO + CO -> Zn + CO2}\] is correct?
Which of the following ore is concentrated by the Froth floatation process?
