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6501.

Discuss the importance of decomposition reaction in metal industry with three points.

Answer»

SOLUTION :(i) MOLTEN `NaCl` is electrolytically decomposed to FORM SODIUM metal.
(ii) Aluminium metal is OBTAINED by electric decomposition of bauxite ore mixed molten Cryolite.
(iii) Carbonate ores are thermally decomposed to give metal oxides which can be reduced to give metal.
Discussion
6502.

Discuss the characteristics of hydrocarbons.

Answer»

Solution :Characteristics of hydrocarbons:
Lower hydrocarbons are gases at room temperature E.g. methane, ethane are gases.
They are colourless and odourless.
The BOILING point of hydrocarbons increases with an increases in the number of carbon atoms.
They undergo combustion reaction with oxygen to FORM `CO_(2)` and WATER.
Alkynes are least REACTIVE when compared to other classes of hydrocarbons.
Alkynes are the most reactive due to the presence of the triple bond.
Alkanes are saturated whereas alkenes and alkynes are UNSATURATED.
They are insoluble in water.
Discussion
6503.

Discovries of isotopes and isobars contradict some of the postulates of _ atomic theory

Answer»

Bohr's
DALTON's
Rutherford's
Thomson's

Solution :Accordingto Dalton s atomic theory, ATOMS of same elements aré identical in all respects, whereas atoms of DIFFERENT elements are different in all respects. But discoirery of ISOTOPES revealed that atoms of same element can have different mass. Discovery of ISOBARS revealed that atoms of different eIements can have same mass. These discoveries of isotopes and isobars contradict the above two postulates of Dalton s atomic theory
Discussion
6504.

Dilute hydrochloric acid is added to test tube containing pieces of zinc. The following observations are recorded. Identify the correct observation.

Answer»

The SURFACE of metal BECOMES lustrous.
The reaction MIXTURE becomes milky.
Odour of pungent SMELLING GAS is experienced.
A colourless and odourless gas is formed.

Solution :A colourless and odourless gas is formed.
Discussion
6505.

Digestion of food in our body is an example of reduction reaction.

Answer»


ANSWER :F
Discussion
6506.

Difine a chemical reaction. Which observations help you to determine whether a chemical reaction has taken place ?

Answer»

Solution :A chemical reaction is a PROCESS that leads to the transformation of one set of chemical substances into ANOTHER. A chemical reaction can be identified by the following observations :
• Change is STATE • Change in colour
• Change in temperature • Evolution of GASES
Discussion
6507.

What is a balanced chemical equation ? Why should a chemical equation be balanced ?

Answer»

Solution :A CHEMICAL EQUATION in which the number of atoms of different elements in the reactant side is equal to the number of atoms on the PRODUCT side is called BALANCED chemical equation.
A chemical equation is balanced to obey the .Law of conservation of mass. which states that mass is neither CREATED nor destroyed during a chemical reaction.
Therefore an equation is to be balanced.
Discussion
6508.

Differentiate the terms Bond dissociation enthalpy & Bond Enthalpy.

Answer»

SOLUTION :1304kJ `MOL^(-1)`
Discussion
6509.

Differentiate soaps and detergents.

Answer»

SOLUTION :`{:(,"SOAPS","DETERGENTS"),(1.,"It is a SODIUM salt of long chain FATTY acids","It is a sodium salt of sulphonic acids"),(2.,"Its effectiveness is reduced when used in hard water","It is effective even in hard water"),(3.,"Soaps are biodegradable","Most of the detergents are non-biodegradable"):}`
Discussion
6510.

Differentiate roasting and calcination process giving one example of each.

Answer»

Solution :ROASTING : Sulphide ore is strongly heated in the presence of air and is converted into METAL oxide.
`2ZnS + 2O_(2) overset("Heat")rarr 2ZnO + 2SO_(2)uarr`
Calcination : Carbonate ore when heated strongly in the ABSENCE of air is converted into metal oxide.
`ZnCO_(3)overset("Heat")rarr ZnO + CO_(2) uarr`
Discussion
6511.

Differentiate reversible and irreversible reactions.

Answer»

SOLUTION :
Discussion
6512.

Differentiate ore and mineral .

Answer»

SOLUTION :
Discussion
6513.

Differentiate Exothermic reaction and Endothemic reaction.

Answer»

SOLUTION :
Discussion
6514.

Differentiate between strong and weak acids. Identify the strong and weak acids from the following list of acids: Hydrochloric acid, acetic acid, formic acid, nitric acid.

Answer»

Solution :Acids which ionize completely in aqueous SOLUTIONS- strongs acids
Acids which ionize partially in aqueous solution- WEAK acids.
Hydrochloric acid, NITRIC acid - strong acid ,acetic acid, Formic acid- Weak acid.
Discussion
6515.

Differentiate between soaps and synthetic detergents.

Answer»

SOLUTION :
Discussion
6516.

Differentiate between saturated and unsaturated hydrocarbons giving one example each .

Answer»

Solution :The organic COMPOUNDS where the carbon atoms are bonded with each other with single bonds are called SATURATED compounds. The saturated carbon chains with HYDROGEN are KNOWN as Alkanes.
Example: methane `CH_4`.
The organic compounds where the carbon atoms are bonded with each other with multiple bonds [double or TRIPLE bonds] are called unsaturated compounds. The hydrocarbons with at least one double bond between carbon atoms are known as Alkenes and the ones with at least one triple bond are known as Alkynes.
Example: Ethene `[C_2H_4]` and Ethyne `[C_2H_2].`
Discussion
6517.

Differentiate between roasting and calcination. Explain the two with the help of suitable chemical equatiosn. How is zinc extracted from its ore?

Answer»

Solution :ROASTING, It is a process in which sulphide ore is heated in the presence of oxygen to convert into oxide.
`2ZnS+3O_(2)to2ZnO+2SO_(2)`
Calcination: It is a process in which carbonate ore is heated in the ABSENCE of AIR to form oxides.
`ZnCO_(3)(s)overset("heat")(to)ZnO(S)+CO_(2)`
By REDUCTION process. Zn can be EXTRACTED from its ore.
Reduction : `2ZnO+ctoZnO+CO_(2)`
Discussion
6518.

Differentiate between roasting and calcination.

Answer»

SOLUTION :DIFFERENCES between CALCINATION and ROASTING
Discussion
6519.

Differentiate between physical and chemical change.

Answer»

SOLUTION :Physical change - no new substance is FORMED, GENERALLY reversible e.g. : Melting of ice. Chemical change - a new substance is formed, generally IRREVERSIBLE. e.g. : Electrolysis of WATER.
Discussion
6520.

Differentiate between metals and non-metals on the basis of their chemical properties.

Answer»

SOLUTION :DIFFERENCES between metals and a non-metals on the BASIS of chemical properties are :
Discussion
6521.

Differentiate between metals and non-metals on the basis of their chemical properties

Answer»

SOLUTION :
Discussion
6522.

Differentiate between metals and non-metals (Based on Physical Properties).

Answer»

SOLUTION :
Discussion
6523.

Differentiate between metal and non-metal on the basis of their chemical properties.

Answer»

SOLUTION : Metals and non-metals can be differentiated on the BASIS of following chemical PROPERTIES :
Discussion
6524.

Differentiate between metal and non-metal on the basis of chemical properties.

Answer»


f

Solution :
Discussion
6525.

Differentiate between electrical conductivity of copper sulphate solution and copper metal .

Answer»

Solution :In COPPER sulphate solution , the electrical conductivity is caused by `Cu^(2+) and SO_(4)^(2-)` IONS , WHEREAS in copper METAL , the elctrical conductivity is caused by the valence ELECTRONS of Cu.
Discussion
6526.

Differentiate between an exothermic reaction and an endothermic reaction . Write one example for each one of these reactions in the form of balanced chemical equation .

Answer»

Solution :Thechemical reaction in which HEAT is released along with the formation of products is CALLED an EXOTHERMIC reaction.
`2J_(2)+O_(2)rarr2H_(2)O+"heat"`
The CHEMICAL reaction in which energy is absorbed is called endothermic reaction.
`2AgCl OVERSET Deltararr2Ag+Cl_(2)`
Discussion
6527.

Differentiate between addition reaction and substitution reaction.

Answer»

Solution :REACTION between unsaturated hydrocarbons with simple substances to form simple SATURATED product are addition reaction.
Reaction in which one or more hydrogen atoms of a saturated hydrocarbon is REPLACED by an atom or a group of atoms are CALLED substitution reaction.
Discussion
6528.

Differentiate between a combination reaction and a decompositionreaction. Write one chemical equation each for these reactions.

Answer»

Solution :The chemical reaction in which a single product is formed from TWO or more reactantsand energy is also evolved , is KNOWN as combination reaction.
Example : `2Mg+O_(2) overset ("Burn")rarr2MgO`
When a single reactant on gaining ENRGY decomposes to give two or more SIMPLER products, such a reaction is CALLED a decomposition reaction.
Example: `CaCO_(3) oversetDeltararrCaO+CO_(2)`
Discussion
6529.

Did Dobereiner's triads also exist in the columns of Newlands' octaves ? Compare and find out.

Answer»

Solution :Dobereiner.s triads also exist in the columns of NEWLANDS. octaves.
Lithium, sodium and potassium forms a Dobereiner.s triad.
Lithium, the first element of this triad is considered as the first element as Newlands. octave, then the eighth element from it is sodium. These elements possesses similar PROPERTIES ACCORDING to the law of triads and the law of octaves.
Similarly, if sodium is considered as the first element then the eighth element from it is potassium. Moreover, sodium and potassium possess similar properties according to both the laws.
Apart from these, some other elements BERYLLIUM (Be), magnesium (Mg) and calcium (Ca) obeys law of triads and the law of octaves.
THUS, Dobereiner.s triads also exist in the columns of Newlands. octaves.
Discussion
6530.

Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.

Answer»

Solution :Dobereiner.s Triads:

Dobereiner.s Triads ALSO exist in the columns of Newlands. OCTAVES. For example, lithium (Li), sodium (Na), potassium (K) CONSTITUTE a Dobereiner.s triad. Also, the second COLUMN of Newlands.classification has the ELEMENTS lithium (Li), sodium (Na) and potassium (K).
Discussion
6531.

Did Döbereiner's triads also exist in the columns of Newlands' Octaves? Compare and find out.

Answer»

Solution :YES, we can identify the following triads:
`H, F, CI`
`Li, Na, K`
`Be, Mg, Ca`
`B, AI, Cr`
The atomic MASS of the middle atom in the above triads is approximately equal to the average mass of the elements on the LEFT and right hand side.
Discussion
6532.

Dibasic acids are stronger than monobasic acids.

Answer»


SOLUTION :NA
Discussion
6533.

Diamond has high melting point, in spite of having covalent bonds.

Answer»

Solution :In diamond, each carbon atom is attached to four other carbon atoms by STRONG covalent bonds and forms three-dimensional tetrahedral structure.
A large AMOUNT of energy is needed to break the network of large NUMBER of covalent bonds.
Hence, diamond has high melting point.
Discussion
6534.

Devendra was told that the elements P,Q and R belong to group 2 , group 14 and group 17, respectivelhy, of the long form of periodic table. Based on this information, he was asked to answer the following questions: (a) What is the valency of (i) element P (ii) element Q and (iii) element R? Give reasons for your answer. (b) What is nature of oxide of (i) element P (ii) element Q and (iii) element R? Give reasons for your answer. (c) Give one example each of (i) element P (ii) element Q and (iii) element R. (d) Name three elements which occur in the same group as element R but exist in three different physical states at room temperature. (e) What values are displayed by Devendra in answering these question?

Answer»

Solution :(a) (i) The valency of element `P` is 2. This can be explained as follows.The elements of group 2 of periodic table have 2 VALENCE electrons each in their atoms. So, the atom of this element can lose 2 valenceelectrons (to some other atom), to attain the nearest inert gas ELECTRON configuration and hence SHOWS a valency of 2.
(ii) The valency of element `Q` is 4. This can be explaine as follows: The elements of group 14 of periodic table have `14-10=14` valence electrons each in theri atoms. An atom of his element can share its 4 valence electrons with 4 more electrons to ACHIEVE the nearest inert gas electron configuration and hence shows a valency of 4.
(III) The valencey of element `R` is 1. This can be explained as follows: The elements of group 17 of periodic table have `17-10=7` valence electrons each in their atoms. An atom of this element having 7 valence electrons can accept 1 more electron to complete the stable, inert gas electron configuration and hence shows a valency of 1.
(b) (i) The elements of group 2 of periodic table are metals.Now,metals form basic oxides. So, the nature of oxide of element `P` is basic.
(ii) The elements of group 14 of periodic table are non-metals. Now, non-metals form acidic oxides. So, the nature of oxide of element `O` is acidic.
(iii) The elements of group 17 of periodic table are also non-metals. Now, non-metals form acidic oxides. So, the nature of oxide of element `R` is acidic.
(c) (i) An example of element `P` of group 2 is magnesium (`Mg`)
(ii) An example of element `Q` of group 14 is carbon `(C)`.
(iii) An example of element `R` of group 17 is chlorine `(Cl)`.
(d) Element `R` occurs in group 17 of periodic table which compirses halogen elements. So, in group 17 of periodic table:
(i) iodine is a solid element.
(ii) bromine is liquid element, and
(iii) chlorine is a gaseous element.
(e) The various values displayed by Devendra in answering these questions are (i) Knowledge of the characteristics of groups of the periodic table, and (ii) Application of knowledge in solving problems.
Discussion
6535.

Deuterium necleus contains

Answer»

`1p+1n`
`2p+0n`
`1p+1e^(-1)`
`2p+2n`

Solution :Deuterium is an isotope of HYDROGEN `""_(1)^(2)H` and contains 1 PROTON and 1 NEUTRON.
Discussion
6536.

……………determines the relation between molecular mass and vapour density.

Answer»

SOLUTION :Avogadro.s LAW
Discussion
6537.

Detergents are used to prepare shampoos and products for cleaning clothes.

Answer»


ANSWER :1
Discussion
6538.

Detergents are sodium or potassium salts of long chains of

Answer»

CARBOXYLIC acids
Sulphonic acids
Aldehydes
Stearic acids

Answer :B
Discussion
6539.

Why detergents are better cleansing agents than soaps ? Explain.

Answer»


ANSWER :T
Discussion
6540.

Design an activity to show a decomposition reaction in which light is used to decompose a reactant. Write chemical equation for the reaction and state its one use.

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Solution :The decomposition reaction carried in the PRESENCE of SUN light is KNOWN as photochemical decomposition. For the ACTIVITY and APPLICATION of photochemical decomposition, consult section 1.5.
Discussion
6541.

Describe two tests to detect carboxylic acid group in an organic compound.

Answer»

Solution :The carboxylic acids can be tested by the following tests :
1. Litmus test. Add a small amount of blue litmus solution to the given COMPOUND. If the litmus solution TURNS red, it indicates that the organic compounds is a carboxylic acid.
2. Sodium bicarbonate test. To a small portion of the organic compound in a test TUBE, and a pinch of solid sodium bicarbonate. Evolution of carbon dioxide with brisk EFFERVESCENCE shows the presence of earboxylic acid.
Discussion
6542.

Describe two examples of different oxidations of ethanol. Name the products obtained in each case

Answer»

Solution :i) When ethanol is heated with copper at 573k, Ethanol if is formed.
`CH_(3)CH_(2)OH to CH_(3)-overset(O)overset(||)C-H+H_(2)`
ii) When Ethanol is oxidised with alkaline POTASSIUM PERMANGANATE solution, ethanoic ACID is formed.
`CH_(3)CH_(2)OH+2(O) to CH_(3)-overset(O)overset(||)C-OH+H_(2)O`
Discussion
6543.

Describe the formation of coal and petroleum.

Answer»

Solution :Coal and petroleum have been formed from biomass which has been subjected to VARIOUS biological and geological processes.
Coal is the remains of trees, ferns and other plants that lived millions of years ago.
These were crushed into the earth, perhaps by earthquakes or volcanic eruptions. They were pressed down by LAYERS of earth and rock. They SLOWLY decayed into coal.
Oil and gas are the remains of millions of tiny plants and animals that lived in the sea. When they DIED, their bodies sank to the sea bed and were covered by silt.
Bacteria ATTACKED the dead remains, turning them into oil and gas under the high pressure.
Thus, the silt was slowly compressed into rock. The oil and gas seeped into the porous parts of the rock and got trapped in it.
Oil and gas were formed by this process.
Discussion
6544.

Describe the following processes: (i) Esterification (ii) Saponification (iii) Hydrogenation.

Answer»

Solution : (i) Esterification : Alcohols are reacted with carbonic acids in the presence of concentrated `H_2 SO_4` to form ester and this process is known as esterification.
Method : Mix ethyl alochol with acetic acid in a test tube, Few drops of conc. `H_2SO_4` is added test tube is heated MILDLY in hot tube of water. Instantaneously sweet smell of ester is diffused in whole room.
`CH_3COOH + C_2H_5OH to CH_3COO_2CH`
(ii) Saponification : Breaking down the fats is called saponification . It is performed by heating vegetable or animal oil with 40% solution of caustic soda . Fats and base react to produce soap and glycerol.

Concentrated common solution is added to crystalisesoap from water . Soap floats on the surface of water after cooling. Soap is extracted from water and desired colour and smell are added and is given desired shape .
(iii) Hydrogenation : Conversion of unsaturated hydrocarbon into saturated hydrocarbons by the addition of hydrogen in the presence of Nickel or polladium as catalystis known as hydrogenation .

INDUSTRIAL APPLICATIONS : This process is used for conversion of vegetable oil into vegetable ghee .
`"Vegetable Oil" + H_2 overset(Ni,476K) to "Vegetable Ghee"`
Vegetableoils havedouble carbonic hand . When hydrogen gas is made to PASS through these in the presence of Nickel acting as catalyst at 473K it converts into solid fat.
Discussion
6545.

Describe the following chemical properties of carbon compounds briefly and give one chemical reaction for each : (i) Combustion (ii) Addition (iii) Substitution (iv) Esterification

Answer»

Solution :(i) Combustion :
`CH_(4) + O_(2) rightarrow CO_(2) + H_(2)O "+ Energy + Light"`
(ii) `CH_(2) = CH_(2) + H_(2) OVERSET(N_(1))rightarrowC_(2)H_(6)`
(III) Substitution
`CH_(3)COOH+C_(2)H_(5)OHoversetHrightarrowCH_(3)COOC_(2)H_(5)+H_(2)O`
Discussion
6546.

Describe the electrolytic refining method for the purification of metals.

Answer»

Solution :The metals OBTAINED from their ores are not very pure. Hence, it is ESSENTIAL to purify the metals. The most widely used method for refining impure metals is electrolytic refining.

Metals such as copper, zinc, tin, nickel, silver and gold are refined by electrolytic process. In this process, the impure metal is made the ANODE and a thin strip of pure metal is made the cathode. A solution of the metal salt is used as an electrolyte. The apparatus is set up as shown in the figure On passing the electric current through the electrolyte, the pure metal from the anode DISSOLVES into electrolyte. An EQUIVALENT amount of pure metal from the electrolyte is deposited on the cathode. For example,
Discussion
6547.

Describe the additon reaction of carbon compounds with its application. State the functionof catalyst in this reaction. How this reaction is different from a substitution reaction?

Answer»

Solution :When any molecule like `H_(2)` adds to unsaturated hydrocarbon because of double and TRIPLE bond, it is known as addition reaction.
`CH_(2) = CH_(2) + H_(2)overset(Ni)rightarrowC_(2)H_(6)`
USE- Hydrogenation of vegetable oils.
Catalyst - Increase the rate of reaction.
SUBSTITUTION reaction `CH_(4)+CI_(2)rightarrowCH_(3)CI + HCI`. In this one atom is replaced by another, two PRODUCTS only one product i addition reaction.
Discussion
6548.

Describe the addition reaction of carbon compounds with its application. State the functions of catalyst in this reaction. How this reaction is different from a substitution reaction? Explain with example.

Answer»

Solution :The ADDITION of hydrogen to an unsaturated molecule to make it saturated is known as hydrogenation or addition reaction.
Example: Ethene undergoes addition reaction to form ethane.
`underset("(Unsaturated)")underset("Ethane")(CH_2 = CH_2 + H_2) underset(N i)overset(200^@C)(rarr) underset("(Saturated"))underset("Ethane")(CH_3 - CH_3)`
This reaction is applied to convert unsaturated vegetable oil into saturated ghee.
`underset(("unsaturated"))("Vegetable oil") underset("200^@C)overset(H_2//N i)(rarr) underset(("Saturated"))("Ghee") "[Hydrogenation"]`
The rate of reaction is increased in the presence of catalyst Ni or PT. This is addition reaction. In substitution reaction, reagent substitutes on atoms or a GROUP of atoms from the reactant instead of addition.
Eg. `CH_4 + Cl_2 underset("Sunlight")(rarr) underset("Chloromethane")(CH_3Cl) + HCl`
Discussion
6549.

Describe how sodium and chlorine form sodium chloride ? Name the type of bonding shown in the structure. (Atomic number : Na = 11, Cl = 17)

Answer»

SOLUTION :
There is IONIC BONDING between sodium and chloride IONS.
Discussion
6550.

Describe how hydro-energy can be converted into electical energy.

Answer»

Solution :High rise dams are constructed on the river to obstruct the flow of water to collect it at suitable height. The stored water has a LOT of potential energy.
The water from a suitable height is ALLOWED to fall on the blades of a TURBINE located at the bottom of a dam through a pipe.
Kinetic eneergy of following water rotates the turbine the armature coil of GENERATOR to rotate rapidly in the magnetic field. Thus HYDROELECTRICITY is generated.
Discussion