Chemistry M.C.Q [1M]

1. Aluminium, Electrolysis.

Explanation:

Aluminium can be obtained from bauxite by Electrolysis. Bauxite is ore of Aluminium and Electrolysis is done to purify aluminium.

3. Both (A) and (B).

Explanation:

Rusting of iron is a combination reaction. It occurs as follows-

Fe + H₂​O + O₂​ → Fe₂​O_3​ × H₂​O

4. Molten or aqueous

Explanation:

Compounds should be aqueous or molten so that they can be easily dissociated into ions.

1. Greater.

Explanation:

As we know, More negative is the standard potential, higher is the probability to oxidise and because of that it has high ability to displace hydrogen from acids.

1. Anode.

Explanation:

On adding electrons to Y, it will get negatively charged and hence will migrate to positive electrode that is anode.

1. Rusting.

Explanation:

The presence of CO₂​ in the atmosphere will do iron oxide rusting. When a drop of water hits an iron object, two things begin to happen almost immediately. First, the water, a good electrolyte, combines with carbon dioxide in the air to form a weak carbonic acid, an even better electrolyte. As the acid is formed and the iron dissolved, some of the water will begin to break down into its component pieces - hydrogen and oxygen. The free oxygen and dissolved iron bond into iron oxide, in the process freeing electrons.

1. Electrolysis.

Explanation:

The process used to decompose compounds using electric current is called electrolysis.

1. Electrolysis.

Explanation:

Ionic substances can be broken down into the elements they are made from by passing electricity through them. The process is called electrolysis.

1. Weak electrophile.

Explanation:

Carbon dioxide is a weak electrophile. It possess very less partial positive charge which are attracted towards electrons.

3. Coulometer.

Explanation:

Coulometry is the technique that determines the amount of matter transformed during an electrolysis reaction, by measuring the amount of electricity (in coulombs) consumed or produced.

2. 193000 C

Explanation:

We know that 22,400cm³ of H_2​ means 1 mole of H₂​.

Now, we know that 2H⁺+ 2e⁻ → H₂​

Hence, for production of 1 mole of H₂​, two moles of e⁻ are required.

And, one mole of e⁻ constitutes 96500 C

Hence, charge or electricity required = 96500 × 2 = 193000 C

1. Oxidation

Explanation:

Rusting of iron involves oxidation.

4. 96500 coulombs

Explanation:

The Faraday constant (named after Michael Faraday) is the magnitude of electric charge per mole of electrons. It is equal to 96500 coulombs.

3. Platinum

Explanation:

Corrosion is a process through which metals in manufactured states return to their natural oxidation states. This process is a reduction-oxidation reaction in which the metal is being oxidized by its surroundings, often the oxygen in air. As platinum is least reactive so it will not corrode.

2. Electrolyte

Explanation:

A dry cell is a type of battery, commonly used for portable electrical devices.A standard dry cell comprises a zinc anode, usually in the form of a cylindrical pot, with a carbon cathode in the form of a central rod. The electrolyte is ammonium chloride in the form of a paste next to the zinc anode.Ammonium chloride is a strong electrolyte. In dry cell, the electrolyte ammonium chloride forms ammonium ion and chloride ions.

2. Reducing agent.

Explanation:

At cathode reduction occurs, therefore, cathode acts as a reducing agent by supplying electrons.

2. Cell emf.

Explanation:

EMF is the difference between the electrode potentials of two electrodes. when no current is drawn through the cell.

1. Separation of charges.

Explanation:

Electric energy is a form of energy, which is created by the movement of electrons. Generally electrons are bound to an atom by the positive force of protons. When for some reason these electrons get detached from their atoms electric energy is produced.

1. Gold

Explanation:

In the activity series, metals are on the top of the series react and corrode easily as these metals are highly reactive like iron corrodes easily in the presence of water and air forming its oxide layer while metals present at the bottom are least reactive and do not corrode easily like gold, silver and platinum are some of them.

2. Weak electrolytes.

Explanation:

Electrolytes which allow small amount of electricity to pass through them are known as weak electrolytes.

4. Lead (II) bromide.

Explanation:

We know that Bromine gas is reddish brown in colour and which can only liberates during electrolysis of Lead (II) bromide (PbBr₂​) During electrolysis of Lead (II) bromide , Positive lead ions (cations) move to the cathode and gain electrons to become lead metal and negative bromide ions (anions) move to the anode and loose an electron to make chlorine atoms. Two bromine atoms then combine and the diatomic bromine gas (Br_2​) is released at the anode.

2. Change in the intensity of illumination into a change in photoelectric current.

Explanation:

In photoelectric effect when monochromatic radiations of suitable frequency fall on the photo-sensitive plate called cathode, the photoelectrons are emitted which get accelerated towards the anode. These electrons flow in the outer circuit resulting in the photoelectric current.

Using the incident radiations of a fixed frequency, it is found that the photoelectric current increases linearly with the intensity of incident light.

1. Chemical energy → electrical energy.

Explanation:

The energy conversion that takes place in a galvanic cell is an chemical to electrical change. Galvanic cells are cells that consist of two dissimilar metals in common contact with an electrolyte.

1. Spongy lead and lead oxide (PbO_2​)

2. The electrolysis proceeds and the rate of liberation remains the same.

Explanation:

Eectrolysis chemical decomposition produced by passing an electric current through a liquid or solution containing ions.The electrolysis proceeds and the rate of liberation remains the same happens when an electrolysis experiment is stopped and the battery terminals are reversed

4. Negative and positive ions both.

Explanation:

A electrolytic solution allows the flow of ions to maintain a balance in charge between the oxidation and reduction vessels while keeping the contents of each separate. With the charge difference balanced, electrons can flow once again, and the reduction and oxidation reactions can proceed.

2. Made as the anode of an electrolytic cell.

Explanation:

Electroplating is a process for coating a conductive object with a thin layer of a material, such as a metal. An electrical current is used to reduce cations of a desired material from a solution onto the object. Electroplating is primarily used for depositing a layer of material to bestow a desired property (e.g., abrasion , wear resistance, corrosion protection, lubricity, aesthetic qualities, etc.) to a surface that otherwise lacks that property. Another application uses electroplating to build up thickness on undersized parts.An article made of an ordinary metal is desired to be coated with gold by electroplating, then gold has to be made as the anode of an electrolytic cell.

4. All of the above takes place.

Explanation:

The corrosion of iron is an electrochemical process. The anode region and cathode region are present in iron. Iron(II) is oxidized to Iron(III) by oxygen and is then converted to rust. At the cathode, oxygen is reduced. The electron flow is from anode to cathode through metal. This is accompanied by the flow of ions through water droplets.

2. Electrotyping.

Explanation:

Electrotyping is one of application of electrolysis, and  is used for the reproduction of some craft work e.g., art work on metals, woodcarving and gramophone records etc.

An impression of the object is taken on a wax block. The wax blocks impression is then coated (sprayed) with a fine power of graphite and is made cathode in an electrolytic bath containing solution of a suitable salt e.g., copper sulfate.

The anode is made of a thin sheet of pure metal e.g., copper metal. The passage of electric current results in the deposition of copper on the wax block impression. After a reasonably thick layer of metal is obtained, the wax is removed by melting.

3. The electrode at which reduction takes place.

Explanation:

In an electrochemical cell, cathode is the electrode, at which reduction takes place and electrons are gained by some species.

Anode is the electrode, at which oxidation takes place and the electrons are lost by some species.

2. Which can be recharged.

Explanation:

A secondary battery cell is one in which chemical energy is converted into electrical energy, but they work only when they are charged by passing electric current through them by some source.

2. Electrolysis is used for manufacturing some gases and compounds.

Explanation:

Electrolysis has wide applications in industries. Some of the important applications are, as follows.

1. Production of hydrogen by electrolysis of water.
2. Manufacture of heavy water.
3. The metals like K, Mg, Al, etc., are obtained by electrolysis of fused electrolytes.
4. Non-metals like hydrogen, fluorine, chlorine are obtained by electrolysis.
5. In this method pure metal is deposited at cathode from a solution containing the metal ions, etc.
6. Compounds like NaOH, KOH, white lead, etc. are synthesised by electrosynthesis method.
7. Electroplating: The process of coating an inferior metal with a superior metal by electrolysis is known as electroplating.

2. 48250 coulomb

Explanation:

Electricity required, Q = No. of equiv. × 96500 coulombs

= 0.5 × 96500 = 48250 C

1. 4.8 × 10⁻¹⁹C

Explanation:

Charge of e⁻ = 1.60 × 10⁻¹⁹C

Charge on M³⁻ = 3 × 1.6 × 10⁻¹⁹C = 4.8 × 10⁻¹⁹C

2. Ampere-hour

Explanation:

The capacity of a cell is measured by the discharging at a constant electric current until it fully drains out for that particular time. Hence, the capacity of the cell/battery is measured by the ampere-hour rating.

2. Chemical energy into electrical energy.

Explanation:

A voltaic cell also known as galvanic cell is an electrochemical cell  that uses spontaneous redox reactions to generate electricity. It consists of two separate half cells. Chemical energy is converted to electrical energy.

4. Effect of dilution on conductance of strong electrolyte can be explained by Arrhenius theory.

3. Electrolysis

Explanation:

Electrolysis is chemical decomposition produced by passing electric current through a liquid or solution containing ions.

3. in all concentrations

Explanation:

Faradays laws are independent of temperature, or concentration Faradays laws are applicable at all concentrations.

2. Sodium reacts more vigorously with water than magnesium and copper.

Explanation:

Sodium reacts more vigorously with water than magnesium and copper.

1. Negative electrode.

Explanation:

Electrochemical cells or galvanic cells are same thing. Anode in galvanic cells is negative electrode where oxidation takes place.

4. 96500 C

Explanation:

Charge of one mole of electrons is known as one faraday which is equal to 96,500 coulombs.

3. Oxidation and reduction respectively.

Explanation:

In a galvanic cell in anode half cell, oxidation of Zn takes place and in cathodic half cell

Cu^2t gets reduced.

2. 96487C

Explanation:

According to the problem: Let the formula required charge n × F

n =  difference of charge on ions

F is constant = 96487C

Here n = 1

Hence required charge = 1 × 96487C

= 96487C.

1. Basic copper carbonate and sulphate.

Explanation:

Architectural structures built with copper corrode to give green verdigris (copper carbonate). It can be a mixture of carbonate and sulfate compounds in various amounts, depending upon environmental conditions such as sulfur-containing acid rain.

3. Outer corroded layer will be removed.

Explanation:

The metals lose their shine and become dull when exposed to air for a long time. Due to the formation of oxides, when the surface is rubbed by a sand paper, then the outer corroded layer is removed.

3. Tin onto iron.

Explanation:

Tin cans, used for storing food, are made by electroplating tin onto iron. Tin is less reactive than iron. Thus, food does not come into contact with iron and

is protected from getting spoilt.