Recent questions tagged metals

Description : science Topic : Metals Fill in the blanks.

Last Answer : 1. An example of a liquid metal is Mercury/gallium. 2. A metal which is soft is sodium. 3. A metal which lacks ductility is sodium. 4. A non-metal which is lustrous is graphite/iodine ... 59. Aluminium+ copper+ magnesium+ manganese is useful in making aircraft bodies. 60. Ornamental gold is an alloy

Description : What are memory alloys? How are they useful?

Last Answer : Certain alloys which regain their original shape when deformed are called memory alloys. Preparation of memory alloys saves energy of melting and recasting of used articles.

Description : Write a note on contributions of Indians to metallurgy.

Last Answer : a) Romans used armour and cutlery made from Indian iron. b) Indian metallurgist Nagarjuna wrote the book Rasaratnakara' in 9th century BC which explained the preparation of various metallic ... near Qutab Minar constructed by Vikramadithya about 1600 years ago has withstood the action of weather.

Description : Why is 6% to 8% copper added to gold in making ornaments?

Last Answer : Pure gold is very soft, it cannot be used to make artistic ornaments. To make it hard, improve the looks and colour, 6 to8% copper is added to ornamental gold.

Description : Which metal is present both in brass and bronze?

Last Answer : Copper

Description : What property of invar steel is used in making pendulums and measuring tapes?

Last Answer : Invar steel has the least co-efficient of linear expansion.

Description : What property of stainless steel is used in making surgical instruments?

Last Answer : Surgical steel is not attacked by mild chemicals easily and it does not corrode.

Description : How are the properties of alloys different from those of metals?

Last Answer : Copper is reddish and zinc is grayish in colour where as brass which is an alloy of copper and zinc is golden yellow in colour. Iron is a magnetic substance but stainless steel, an alloy of iron is non magnetic.

Description : Give reason: Metals belonging to the same group form good alloys.

Last Answer : As metals belonging to the same group in the periodic table have similarities in electronic configuration.

Description : Why are alloys made?

Last Answer : Alloys give desired properties to the metal. It improves the properties of metals.

Description : How is an alloy formed?

Last Answer : Alloysare prepared by mixing the various metals in their molten state and cool them to room temperature. Better quality can be made by mixing metals using ultrasonics.

Description : What is an alloy?

Last Answer : An alloy is a homogenous mixture of two or more metals or metal with a non-metal. Example: Brass is an alloy of two metals copper and zinc. Steel is an alloy of a metal iron and non-metal carbon.

Description : Briefly explain the electrolytic refining of copper.

Last Answer : Copper is purified by electrolytic refining. The apparatus consists of an electrolytic tank containing copper sulphate solution as electrolyte. A set of thick blocks of impure copper is made anode ... anode becomes thinner and pure cathode becomes thicker. The impurities collect at the bottom.

Description : What is electrolytic refining?

Last Answer : Electrolytic refining is a technique of ultra refining of metal. In this method, impure metal is taken as anode and pure metal are taken as cathode. Electric current is passed through the electrolyte to obtain pure metal at the cathode.

Description : Explain the process of zone refining. Name one metal refined by this method.

Last Answer : The apparatus used for zone refining consists of a circular heater fitted around the rod of impure metal at one end. The circular heater is slowly moved to the other end. At the heated zone, ... in solid metal passes into the adjacent molten part. A metal refined by zone refining is germanium.

Description : What is meant by zone refining or fractional crystallization?

Last Answer : Zone refining is a technique of obtaining ultra pure metal. It is based on the principle of differences in solubility of impurities in liquid and solid states of the metal.

Description : What is meant by liquation process?

Last Answer : Liquation is a process of obtaining ultra pure metal. It is based on the principle that metals are readily fusible where as the impurities are infusible at the temperature at which the metals fuse.

Description : Mention the methods of obtaining ultra pure metal.

Last Answer : a) Fractional crystallization or zone refining. b) Vacuum melting c) Distillation d) Chemical vapour deposition e) Liquation process

Description : Name the process by which the refining of aluminium is done. Name the material used for the process.

Last Answer : Aluminium is refined by electrolytic refining. Carbon lining acts as the cathode and the graphite rods act as anode.

Description : Briefly explain the extraction of aluminium from alumina with chemical equations.

Last Answer : Aluminium oxide dissolved in molten cryolite is taken in a chamber with gently sloped base.The inner wall is made of carbon lining. Graphite rods are introduced in the electrolyte bath. The carbon lining ... is passed. Molten aluminium collects at the lining and flows out of the gently sloped base.

Description : What is cryolite? Write its chemical formula.

Last Answer : Cryolite is chemically sodium aluminium fluoride. Its molecular formula is Na3AlF6.

Description : What is the role of molten cryolite in the extraction of aluminium?

Last Answer : When pure alumina is mixed with molten cryolite, it forms an electrolyte at 1223K. Molten cryolite also acts as a solvent for alumina.

Description : What is the difficulty in obtaining aluminium from alumina?

Last Answer : Pure alumina melts at 2323K. At this temperature, aluminium vapourises and there will be considerable loss. It consumes more energy and also molten aluminium is not a very good conductor of electricity.

Description : Why is pure alumina needed for the extraction of aluminium?

Last Answer : For electrolysis of we need pure alumina. Hence bauxite is converted into alumina by chemical process.

Description : Why is extraction of aluminium not commercially viable by using reducing agents like coke? OR Coke is used in the extraction of iron but not in the extraction of aluminium. Why? OR Aluminium cannot be extracted by heating bauxite and coke. Why?

Last Answer : Oxygen of aluminium oxide cannot be easily taken away by reducing agents like coke.

Description : What is alumina? Write its molecular formula.

Last Answer : Alumina is chemically hydrated oxide of aluminium. Its formula is Al2O3.2H2O.

Description : What is a mordant?

Last Answer : A mordant is a substance which helps to bind the dye to the cloth.

Description : Mention the uses of aluminium salts.

Last Answer : a) Aluminium salts are used as mordant in textile industry (to bind the dye to the cloth). b) Potash alum is used to prevent bleeding from small cuts by coagulating the blood at the surface.

Description : Name the impurities present in cast iron. How can these impurities be removed?

Last Answer : Cast iron contains sulphur, phosphorous, silicon and carbon. The impurities present in the blast furnace can be removed by using Bessemer converter, open hearth process or electric furnace.

Description : Mention the uses of cast iron.

Last Answer : Cast iron is used for: a) Making stands for wooden benches and desks. b) Making dosa pan c) Making lid for covering manholes of sewage system. d) Making machinery parts.

Description : How is the slag obtained in the extraction of iron useful?

Last Answer : Slag obtained in blast furnace is used as one of theraw materials of glass and cement.

Description : Why is slag collected above molten iron?

Last Answer : Slag is lighter than molten iron and collects above molten iron. Slag prevents oxidations of molten iron back into iron oxide.

Description : What is the role of coke in the extraction of iron?

Last Answer : Coke is a good reducing agent. It reduces iron oxide to iron. It is also a good fuel which supplies heat energy for the chemical reactions.

Description : Why is flux used in the blast furnace?

Last Answer : Flux in extraction of iron is limestone. Limestone reacts with the sand present as impurity in the ore forming calcium silicate which is taken out of the blast furnace as slag.

Description : What happens when lime stone is not added during the extraction of iron?

Last Answer : If limestone is not added to charge during the extraction of iron, the blast furnace will get blocked.

Description : State the role of lime stone in the extraction of iron from haematite. Or Why is lime stone added during the extraction of iron?

Last Answer : Limestone reacts with the sand present as impurity in the ore forming calcium silicate which is taken out of the blast furnace as slag.

Description : What is charge?

Last Answer : The mixture of haematite, lime stone and coke is called charge.

Description : How is iron ore concentrated?

Last Answer : The chief ore of iron is haematite. Haematite ore is concentrated by hydraulic washing. The crushed ore is washed with a stream of water, lighter gangue particles will be washed away and the heavy iron ore particles also with silica settles down during washing.

Description : What happens when? a) A cleaned iron plate or iron nail is kept in 10g of copper sulphate solution. b) A pinch of mercuric oxide is kept in a test tube. c)A small crystal of silver nitrate is dissolved in distilled water and a drop of ammonium hydroxide & a pinch of glucose powder are added.

Last Answer : a) A cleaned iron plate or iron nail is kept in 10g of copper sulphate solution. After a few hours a coating of copper is seen on iron nail/plate. It is based on displacement reaction. ... on the inner walls of the test tube. Aldehyde group in glucose reduced silver nitrate to metallic silver.

Description : Explain the following terms with reference to metallurgy.

Last Answer : a) Gangue The unwanted impurities present in the ore are called gangue. b) Concentration of ore The process of removing the gangue particles to increase the percentage of desired component of the ore ... flux. f) Slag The substance formed by the combination of impurities like sand is called slag.

Description : Define metallurgy.

Last Answer : The technology of extraction of metals from their ores and refining them to required form is called metallurgy.

Description : Give reason: Gold occurs in native form.

Last Answer : Gold is low in the reactivity series. It is least reactive or unreactive. Hence gold is found in free state.

Description : What is an ore?

Last Answer : The compound of a metal from which the metal can be extracted economically is called an ore.

Description : Which gas is always produced if a metal reacts with water or dilute acid?

Last Answer : Hydrogen

Description : Name some metals which do not displace hydrogen from dilute acids.

Last Answer : Platinum, gold, silver, mercury & copper do not displace hydrogen from dilute acids.

Description : Give reason: Some metals are more reactive than others.

Last Answer : Metals are electropositive and have tendency to donate electrons. Some elements give up their valence electrons and hence more reactive.

Description : In a solution of silver nitrate, a copper plate was dipped. After some time, silver from the solution was deposited on the copper plate. Which metal is more reactive – copper or silver?

Last Answer : More reactive metal displaces a less reactive metal. Hence copper metal is more reactive.

Description : Give reason: Iron displaces copper from copper sulphate solution.

Last Answer : Iron is more reactive than copper. Hence it displaces copper from copper sulphate solution.

Description : Give reason: Aluminium / Iron become passive when immersed in concentrated nitric acid.

Last Answer : Since concentrated nitric acid is a powerful oxidising agent, it forms a protective oxide layer on the metal instantly

Description : What happens when a iron nail or a piece of aluminium wire is dipped in concentrated nitric acid?

Last Answer : Iron nail or aluminium wire does not react with concentrated nitric acid. It makes iron more passive.