b. Molecular formula of the common ore of aluminium.
c. The oxide that forms salt and water by reacting with both acid and base.
d. The device used for grinding an ore.
e. The nonmetal having electrical conductivity.
f. The reagent that dissolves noble metals.
a. Sodium amalgam, commonly denoted as Na(Hg), it is an alloy of mercury and sodium.
b. Bauxite(Al2O3.2H2O) is the common ore of aluminium.
c. Metal oxides which react with both acids as well as bases to produce salts and water are also known as amphoteric oxides. For example: Al2O3 is an amphoteric oxide. An amphoteric compound is a molecule or ion that can react both an acid as well as a base to produce salt and water.
d. The device used for grinding an ore is grinding mill.
e. Graphite an allotrope of carbon is a good conductor of electricity.
f. Aqua Regia is 1:3 mixture of concentrated nitric and hydrochloric acids. It dissolves noble metals such as gold, palladium, and platinum.
a. Potassium bromide
2. Soluble in water
3. No chemical reaction
4. High ductility.
a. Potassium bromide
Soluble in water
No chemical reaction
Identify the pairs of metals and their ores from the following.
Explain the terms.
a. Metallurgy: The various processes involved in the extraction of metals from its ores and refining is called metallurgy.
The major steps involved for the extraction of a metal from its ore are:
(i) Concentration of ores (or enrichment of ore)
(ii) Conversion of concentrated ore into metal
(iii) Refining (purification) of impure metal
b. Ores: Those minerals from which metals can be extracted conveniently and profitably.
c. Minerals:” A mineral is an element or chemical compound that is normally crystalline and that has been formed as a result of geological processes” (Nickel, E. H., 1995).
“Minerals are naturally-occurring inorganic substances with a definite and predictable chemical composition and physical properties.” (O’ Donoghue,1990).
“A mineral is a naturally occurring homogeneous solid, inorganically formed, with a definite chemical composition and an ordered atomic arrangement” (Mason, et al,1968).
“These… minerals …can be distinguished from one another by individual characteristics that arise directly from the kinds of atoms they contain and the arrangements these atoms make inside them” (Sinkankas, 1966).
“A mineral is a body produced by the processes of inorganic nature, having usually a definite chemical composition and, if formed under favorable conditions, a certain characteristic atomic structure which is expressed in its crystalline form and other physical properties” (Dana & Ford,1932).
“Every distinct chemical k occurring in inorganic nature, having a definite molecular structure or system of crystallization and well-defined physical properties, constitutes a mineral species” (Brush & Penfield
d. Gangue: – is the unwanted impurities like rock material, dust, soil, sand, earthy particles, limestone, mica etc. present in an ore.
Write scientific reasons.
a. Lemon or tamarind is used for cleaning copper vessels turned greenish.
b. Generally the ionic compounds have high melting points.
c. Sodium is always kept in kerosene.
d. Pine oil is used in froth flotation.
e. Anodes need to be replaced from time to time during the electrolysis of alumina.
a. Copper vessels turned greenish due to the formation of copper carbonate layer.
The citric acid present in the lemon or tamarind neutralizes the basic copper carbonate and dissolves the layer.
That is why, tarnished copper vessels are cleaned with lemon or tamarind juice to give the surface of the copper vessel its characteristic lustre.
b. In an ionic compound there is strong electrostatic force of attraction between oppositely charged ions.
To overcome these forces a considerable amount of energy is needed.
Therefore, ionic compounds have high melting points.
c. Sodium is a very reactive metal. It is kept in kerosene to prevent it from coming in contact with oxygen and moisture.
If this happens, it will react with the moisture present in air and form sodium hydroxide.
This is a strongly exothermic reaction and lot of heat is generated.
d. Pine oil is added in the froth flotation method to create froth or bubble so that metal can be purify easily because pine oil prevents the ore from gangue for further mixing.
Pine oil also acts as the best substance for forming froth for the minerals.
It also increases the non wettability of mineral particles.
e. In the electrolysis of alumina, graphite rod is used as anode.
During the electrolytic reduction of alumina, aluminium is produced at the cathode and oxygen gas is evolved at the anode.
This gas reacts with the graphite rods (anode) and forms carbon dioxide.
Thus, the graphite rods are continuously eroded.
Hence, the graphite rods i.e. anodes be replaced from time to time during the electrolysis of fused alumina.
When a copper coin is dipped in silver nitrate solution, a glitter appears on the coin after some time. Why does this happen? Write the chemical equation.
Copper is more reactive than silver. Hence, displacement reaction occurs.
When copper coin is dipped in silver nitrate solution, it forms copper nitrate and silver metal.
A shining white deposit of silver metal is formed on copper coin.
The grey solid crystal(glitters) of Ag metal appears on the copper coin and solution turns blue in colour.