General Principles and Processes of Isolation of elements

Carbon (as coke or charcoal), though a reducing agent, is not used in the extraction of aluminium because ____.

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Carbon (as coke or charcoal), though a reducing agent, is not used in the extraction of aluminium because the temperature needed for carbon reduction is too high to be economical.

________ is a half reaction that shows reduction.

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Cu2+ + 2e- → Cu. This is a half reaction showing reduction, as copper ions gain two electrons to become copper metal (atomic form). Reduction is gain of electrons.

If reactants and products of two reactions are put together in a system and the net ΔG of the two possible reactions is negative, the overall reaction will take place. These reactions are called ____.

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If reactants and products of two reactions are put together in a system and the net ΔG of the two possible reactions is negative, the overall reaction will take place. These reactions are called coupled reactions.

Which of the gas is used as fuel in extraction of zinc from zinc blende in vertical retorts?

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Producer gas is used as fuel in extraction of zinc from zinc blende.

Apart from the statement '____', all other statements given below are correct.

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Apart from the statement “Coinage alloy is a mixture of nickel and iron.” all other statements given are correct. Coinage is a mixture of copper and nickel.

In the electrolysis of aluminium, the anodes in the cell have to be replaced frequently because ____.

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The anodes in the cell have to be replaced frequently because they are burned away by O2 reacting with the carbon anode to form CO2 gas.

The most common ore for iron is ____.

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The most common ore for iron is haematite. The magnetic properties of iron make it easy to separate steel products from other waste. This makes it possible for its efficient recycling.

The concentrated ore must be converted into a form which is suitable for ____. Generally, the ____ore is converted to oxide before reduction.

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The concentrated ore must be converted into a form which is suitable for reduction. Generally, the sulphide ore is converted to oxide before reduction.

In extraction of iron, Carbon monoxide acts as ____.

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In extraction of iron, Carbon monoxide acts as reducing agent.

When haematite is reduced in Blast furnace ____ gas is released.

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Fe2O3 + 3CO →2 Fe + 3 CO2

During the formation of metal oxides from metal and oxygen, what happens to the change in Gibbs free energy with the little increase of temperature?

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A metal makes a positive ion. So, oxygen with its electronegativity is more attracted to metals than to other non-metals. Hence, with a little increase in temperature, the ΔG increases.

In metallurgy, the Ellingham diagrams are useful in attempting to predict the conditions under which a metal ore will be ____ to the metal.

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In metallurgy, the Ellingham diagrams are useful in attempting to predict the conditions under which a metal ore will be reduced to the metal.

The undesired material which is present with the element in its ore is known as ____.

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The undesired material which is present with the element in its ore is known as gangue.

Other than ____, all other are the methods for removal of unwanted materials (e.g. sand, clays, etc.) from the ore.

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Zone refining is a method for obtaining metals of high purity and not a method for removal of unwanted materials (e.g. sand, clays, etc.) from the ore. It is based on the principle that the impurities are more soluble in the melt, than in the solid state of metal.

Ellingham diagrams are plots drawn between ____ and ____ for formation of oxides.

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Ellingham diagrams are plots drawn between Change in Gibbs free energy and temperature for formation of oxides.

Sometimes there are two sulphides in an ore, which are separated by using ____.

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Sometimes there are two sulphides in an ore, which are separated by using depressant. In case of an ore containing ZnS and PbS, the depressant used is NaCN. It prevents ZnS from coming to the froth but allows PbS to come with the froth.

In the froth floatation method, pine oils, fatty acids, xanthates, etc. are ____ whereas cresols and aniline are used as ____.

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In the froth floatation method, pine oils, fatty acids, xanthates, etc. are collectors whereas cresols and aniline are used as froth stabilizers. Collectors enhance non-wettability of the mineral particles and froth stabilizes, stabilize the froth.

Which of the following is not an ore of iron?

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Dolomite is ore of Magnesium and calcium, whereas rests three are ores of iron.

A reaction proceeds only when the value of ΔG is ____If ΔS is positive, on ____ the temperature T, the value of TΔS will increase and then G becomes negative.

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A reaction proceeds only when the value of ΔG is negative. If ΔS is positive, on increasing the temperature T, the value of TΔS will increase and then G becomes negative. For an irreversible (spontaneous) reaction ΔS > 0, therefore, any increase in temperature will make H < TΔS, giving a negative value to ΔG (ΔG = ΔH – TΔS). Hence, so the reaction will proceed.

Of the options given, except ____, all other methods are used for obtaining metals of high purity.

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Other than calcination all other methods are used for obtaining metals of high purity. Some other methods of refining are zone refining, electrolysis and chromatographic methods.

Distillation is very useful for low boiling metals like____.

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Distillation is very useful for low boiling metals like zinc and mercury.

Siderite is ____ ore of iron.

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Siderite (FeCO3) is carbonate ore of iron.

A few elements like carbon, sulphur, gold and noble gases, occur in ____ state while others in ____ form, in the earth’s crust.

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A few elements like carbon, sulphur, gold and noble gases, occur in free State while others in combined form in the earth’s crust. The reason for the free occurring elements is that they are not very reactive to combine with the other freely available elements like oxygen, nitrogen, etc.

In the Ellingham diagram, if two metals are present, two equilibriums have to be considered, so that the metal with the more negative ΔG____ and the other gets ____.

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In the Ellingham diagram, if two metals are present, two equilibriums have to be considered, so that the metal with the more negative ΔG reduces, and the other gets oxidized. The metal with more negative ΔG will be more reactive than the one which gets oxidized.

____is a half reaction where oxidation takes place.

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2Cl--2e- → Cl2. Here, two Cl- ions loose two electrons to give a molecule of chlorine. Oxidation is loss of electrons.

97 % zinc is known as ____.

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97% zinc is known as zinc spelter.

Titanium is produced by reducing titanium (IV) chloride using a more reactive metal such as ____or____.

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Titanium is produced by reducing titanium (IV) chloride using a more reactive metal such as sodium or magnesium. The more reactive sodium metal releases electrons easily by forming its ions: These electrons are used to reduce the titanium (IV) chloride to its metal form.

____is not a factor for choosing a substance for reducing a particular ore.

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The percentage of metal present is not a factor for choosing a substance for reducing a particular ore. However small or large be the quantity of metal present in the ore, once decided, the reducing substance will remain the same. Method of extraction will certainly depend on the quantity of metal present in the ore.

During operation of electrochemical cells, ____energy is transformed into ____ energy.

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During operation of electrochemical cells, chemical energy is transformed into electrical energy. It is expressed mathematically as the product of the cell's emf (electromotive force), Ecell and the electric charge, Ctrans transferred through the external circuit. Electrical energy = EcellCtrans

The entire scientific and technological process used for isolation of the metal from its ores is known as ____.

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The entire scientific and technological process used for isolation of the metal from its ores is known as metallurgy. All the other options are various steps in metallurgy.

Class 12th Chemistry - 6 General Principles and Process of Isolation of Elements MCQs
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Class 12th Chemistry - 6 General Principles and Process of Isolation of Elements MCQs