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1501.

Why are metals good conductors of electricity.

Answer»

SOLUTION :Metals are GOOD CONDUCTORS of electricity because they contain free electrons. These free electrons move easily through the metal and conduct ELECTRIC current.
Discussion
1502.

two elements that have two electrons in their outermost shells

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SOLUTION :MAGNESIUM (MG) and CALCIUM (CA)
Discussion
1503.

Write the equations to represent the reaction of sodium hydroxide with hydrochloric acid.

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SOLUTION :`HCl+NaOHtoNaCl+H_(2)O`
Discussion
1504.

What sould be used as the anode, cathode and electrolyte in the process of electroplating of iron by nickel and why ?

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SOLUTION :METAL to be electroplated is TAKEN as CATHODE.
Discussion
1505.

While cooking, if the bottom of the vessel is getting blackend on the outside, it means that:

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the food is not cooked completely.
the FUEL is not BURNING completely.
the fuel is wet.
the fuel is burning completely.

Solution :the fuel is not burning completely.
Discussion
1506.

When Potassium Iodide solution is added to a solution of Lead Nitrate,then what is color of precipitate of Lead Iodide

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Black
Blue
Red
Yellow

Answer :D
Discussion
1507.

Write the valency and usual number of electrons of Group 18 of the Periodic Table.

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SOLUTION :VALENCY = 0
No. of ELECTRONS = 8
Discussion
1508.

Which of the following is not a mineral acid?

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glycolic acid
lactic acid
citrus acid
tartaric acid

Solution :Lactic acid `CH_3 - OVERSET(OH)overset(|)CH-COOH` is present in SOUR MILK.
Discussion
1509.

What are hydrocorbons? Give examples.

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Solution :COMPOUNDS of carbon and hydrogen are called hydrocarbons. Methane, Ethane, Butane , Ethyne, PROPANE, BENZENE, PETROLEUM products all are examples of hydrocarbons.
Discussion
1510.

Which of the following is (are) not natural acid (s) ?

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TARTARIC ACID
Hydrochloric acid
Nitric acid
Oxalic acid

ANSWER :B::C
Discussion
1511.

What is called diagonal relationship ?

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Solution :The similarities in properties between certain elements of different periods placed diagonally to ONE ANOTHER in a PERIODIC table are called DIAGONAL relationship.
Discussion
1512.

Which among the following is not a base ?

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a)NaOH
b)KOH
`c)NH_(4)OH`
`d)C_(2)H_(5)OH`

Solution :`C_(2)H_(5)OH`
Discussion
1513.

When a piece of iron is placed in a solution of copper sulphate, the blue color of the solution is changed to

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yellow
brown
green
ORANGE

ANSWER :C
Discussion
1514.

The strength of an acid or an alkali can be tested by using a scale called the which gives the _______measure of hydrogen ion concentration in a solution.

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SOLUTION : PH. For acidic solutions the pH is < 7 and for an ALKALI, the pH > 7.
Discussion
1515.

Which among the following is the graphical representation of a reaction is the DeltaHfor the forward reaction is twice the activation energy of the I step and activation energy of the II step is half of the I step

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ANSWER :C
Discussion
1516.

The scientist who classified elements on the basisof atomic number.

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SOLUTION :HENRY Mosele y .
Discussion
1517.

Which one of the following elements of period 2 has high electron affinity?

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Lithium
Carbon
Fluorine
Neon

ANSWER :C
Discussion
1518.

Write the balanced chemical equation and identify the type of reaction : Magnesium(s) + Hydrochloric acid(aq) to Magnesium chloride(aq) + Hydrogen(g)

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SOLUTION :`Mg(s)+ 2HCl(aq) to MgCl_(2)(aq)+H_(2)(g)`
GIVEN reaction is a displacement reaction.
Discussion
1519.

Which one of the following does not increase while moving down a group of the periodic table?

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ATOMIC radius 
Metallic CHARACTER 
Valence electrons 
Number of SHELLS in an element 

ANSWER :C
Discussion
1520.

The valency of an element is determined by the number of ________electrons present in theoutermost shell of an atom.

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SOLUTION :VALENCE
Discussion
1521.

What type of compound is formed by the reaction between acetic acid and an alcohol?

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SOLUTION :An ESTER (ETHYL ethanoate) is FORMED.
Discussion
1522.

Write the IUPAC names of thefollowing:CH_3 - oversetunderset(|)(CH_3)(C)H - CH_3

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SOLUTION :2-Methylpropane
Discussion
1523.

Which two metal do not corrode easily?Give an example in each case to support that (i) Coorosion of some metals is an advantage. (ii) corrosion of some metals is a serious problem.

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SOLUTION :Gold and platinum
(i) A thin IMPERVIOUS layer of aluminium oxide forms a protective layer which process the aluminium metal underneath from further damage.
(II) Corrosion of iron is a serious problem. Every year enormous amount of MONEY is spent to replace damaged iron and STEEL structures.
Discussion
1524.

Which layer is formed on Al, when it is exposed to air ?

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`Al_3O_2`
`Al_2O_3`
`ALO`
`ALN`

SOLUTION :`Al_3O_2`
Discussion
1525.

Which of the following reaction involves the combination of two elements?

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`CaO + CO_(2) to CaCO_(3)`
`4Na + O_(3) to 2Na_(2) O`
`SO_(2) + 1/2 O_(2) to SO_(3)`
`NH_(3) + HC1 to NH_(4) C1`

Answer :B
Discussion
1526.

Which of the following statements are usually correct for carbon compounds ? These are good conductors of electricity. are poor conductors of electricity. have strong forces of attraction between their molecules.do not have strong forces of attraction between their molecules.

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(i) and (iii)
(ii) and (iii)
(i) and (IV)
(ii) and (iv)

Solution :Carbon compounds are of covalent nature. That is why thse are poor CONDUCTORS of ELECTRICITY (ii) and do not have STRONG FORCES of attraction (iv)
Discussion
1527.

What is called gangue? On which factors, the process used for removing the gangue from the ore depends?

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Solution :ORES obtained from the earth does not contain metal element only, but contains large AMOUNT of impurities such as soil, sand, undesired other substances, etc. are called GANGUE. The process used for removing the gangue from the ORE are based on the differences between the PHYSICAL or chemical properties of the gangue and ore.
Discussion
1528.

Which of the following methods is suitable for preventing an iron frying pan from rusting?

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Applying greases
Applying a coating of zinc
Applying PAINT
All of the above

Solution :The suitable method for preventing an iron frying pan from RUSTING is ( c) applying a coating of zinc. Applying grease will spoil the food to be cooked in frying pan. Also, we cannot apply paint because it will gradually COME out when the frying pan is heated on a gas STOVE while cooking.
Discussion
1529.

Which of the following cannot show acidic nature ?

Answer»

`H_(2)CO_(3)`
`CaCO_(3)`
HCl
`HSO_(4)^(-)`

Answer :B
Discussion
1530.

Write the molecular formula, electron dot structural formula and structural formula of ethyne.

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Solution :`(i) C_2H_2 (II) H:C::CH (iii) H - C -= C - H`
Discussion
1531.

Write the chemical equation involved in the following reaction White washing

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Solution :In white washing, quick lime reacts with WATER to form SLAKED lime :
`CaO+H_(2)O to CA(OH)_(2)+"HEAT"`
Discussion
1532.

When Magnesium is burnt in air, awhile ash remain as left over. What is this?

Answer»

`MgO_(2)`
MgO
MG
`Mg_(3)O`

Solution :`2Mg + O_(2) to UNDERSET (white" "ASH) (2MgO)`
Discussion
1533.

Write the molecular, electron-dot , and structural formula of ethyne.

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SOLUTION :MOLECULAR formula of ethyne `= C_(2)H_(2)`
Electronic formula `=H ..Cv DOTS vdotsC..H`
Structural formula `= H-C-=C-H`
Discussion
1534.

Which of the following are combination reactions ? "(i) "2KClO_(3)overset("Heat")(to)2KCl+3O_(2)"(ii) "MgO+H_(2)toMg(OH)_(2) "(iii) "4Al+3O_(2)to2Al_(2)O_(3)"(iv) "Zn+FeSO_(4)toZnSO_(4)+Fe

Answer»

(i) and (iii)
(iii) and (iv)
(II) and (iv)
(ii) and (iii)

Solution :Combination reactions are those in which TWO or more reactants react to GIVE one PRODUCT only.
Discussion
1535.

Which of the following is not a compound?

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sugar
common Salt
DIAMOND
PLASTER of PARIS

SOLUTION :diamond
Discussion
1536.

What is an amalgam ?

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SOLUTION :An AMALGAM is an ALLOY of MERCURY with some other METALS.
Discussion
1537.

The silver anklet has gor tarnished when exposed to air due to the formation of silver oxide(Ag_(2)O)

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SOLUTION :FALSE
CORRECT STATEMENT:The silver anklet has got tranished when exposed to air due to the formation of silver sulphide `(Ag_(2)S)`
Discussion
1538.

What do you mean by staionary orbit ?

Answer»

Solution :ACCORDING to Borh's atomic model an ELECTRON does notlose its energyas long as it revolein a particular ORBIT . These orbits are CALLED staionary orbits.
Discussion
1539.

Why are detergents better cleansing agents than soaps?

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Solution :DETERGENTS work as cleansing agent in hard and SOFT water both because the charged ends of detergents do not FORM insoluble precipitates with calcium and MAGNESIUM IONS in hard water.
Discussion
1540.

We oftenfindsmallpacketsofsilicagelin foodpacksleatherandelectronicgoods . Whatproperty of silicagelis thereasonfor itsextensiveuse ?

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SOLUTION :Hygroscopicproperty
Discussion
1541.

What is the chemical formula for Plaster of Paris ? How is it prepared ? State the common and chemical names of the compound formed when Plaster of Paris is mixed with water.

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Solution :The CHEMICAL formula for Plaster of Paris `CaSO_(4).(1)/(2) H_(2)O` It is prepared by heating gypsum at 373 K as shown by the following equation :
`UNDERSET("Gypsum")(CaSO_(4).2H_(2)O) OVERSET(373 K)underset(Delta)rarr underset("Plaster of Paris")(CaSO_4 . (1)/(2)H_2O +(3)/(2))H_2O`
When Plaster of Paris is mixed with water. gypsum (common name) if FORMED again. Chemically it is known as calcium sulphate dihyrate.
`CaSO_(4).(1)/(2) H_(2)O + 3/2 H_(2)O rarr underset("Gypsum" )(CaSO_(4)2H_(2)O)`
Discussion
1542.

Zinc is the metal which lies in the middle of the activity series. This metal is extracted from its sulphide ore. Outline the steps involved in the process of extraction of zinc metal with the help of balanced chemical equation for each step.

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Solution :Steps :
(i) ROASTING : Sulphide ores are converted into oxides by heating strongly in the presence of excess AIR.
`2ZnS + 3O_(2) overset("HEAT")rarr 2ZnO + 2SO_(2)`
(ii) Reduction : Metal oxides are then reduced to the corresponding metal by using suitable REDUCING agent (carbon).
`ZnO + C rarr Zn + CO`
Discussion
1543.

When a true solution is filtered

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the filtrate obtained is turbid
a solid RESIDUE is left on the filter paper
the solute gets SEPARATED from the solvent
the filtrate is as good as the true SOLUTION .

Answer :D
Discussion
1544.

What is meant by homologous series of carbon compounds ? Write the general formula of (i) alkenes, and (ii) alkynes. Draw the structures of the first member of each series to show the bonding between the two carbon atoms.

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Solution :A homologous series is a series of organic compounds that BELONGS to the same FAMILY (i.e., POSSESSES the same functional group) and show similar CHEMICAL properties. The members of this series are called homologous, they differ from each other by the number of `CH_(2)` units in the main Carbon chain.
General Formula
Alkenes : `C_(n)H_(2n)`, Alkynes : `C_(n)H_(2n-2)`
STRUCTURES
The first member of alkenes is ethene and its structure is given below.
`H-underset(H)underset(|)(C )=overset(H)overset(|)(C )-H`
The first member of alkenes is ethene and its structure is given below.
`H - C -= C- H`
Discussion
1545.

When a drop of dilute hydrochloric acid is added to a blue litmus paper, the colourof the litmus paper changes to

Answer»

RED
yellow
green
ORANGE

ANSWER :A
Discussion
1546.

What happens when zinc granules are treated with dilute solution of H_(2)SO_(4),HCl,HNO_(3),NaClandNaOH? Also write the chemical equations if reaction occurs.

Answer»

Solution :The reaction of Zn granules with
(i) DILUTE `H_(2)SO_(4)`
`Zn(s)+H_(2)SO_(4)(aq)rarrZnSO_(4)(aq)+H_(2)(g)`
(ii) dilute HCl
`Zn(s)+2HCl(aq)rarrZnCl_(2)(aq)+H_(2)(g)`
(III) dilute `HNO_(3)`
Reaction with dilute `HNO_(3)` is DIFFERENT as compared to other acids because nitric acid is an oxidising agent and it oxidises `H_(2)` gas evolved to `H_(2)O`.
`4Zn(s)+10HNO_(3)(aq)rarr4Zn(NO_(3))_(2)(aq)+5H_(2)O(l)+N_(2)O(g)`
(iv) NaCl solution
`Zn(s)+NaCl(aq)rarr"No reaction"`
(v) NaOH solution
`Zn(s)+2NaOH(aq)rarrunderset("Sodium zincate")(Na_(2)ZnO_(2)(aq))+H_(2)(g)`
Discussion
1547.

Which one of the following is least reactive element?

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AU
Fe
Ca
Na

Answer :Au
Discussion
1548.

Write equations for the laboratory preparation of: lead sulphate using dilute sulphuric acid.

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Solution :`PB(NO_(3))_(2)+H_(2)SO_(4)toPbSO_(4)+2HNO_(3)`
Discussion
1549.

Which of the following has a triple bond.

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`C_(2)H_(6)`
`C_(3)H_(4)`
`C_(3)H_(8)`
`C_(3)H_(6)`

ANSWER :2
Discussion
1550.

The vertical columns in th eperodic table are called __________ while the horizontal rows are called ____________ .

Answer»

SOLUTION :GROUPS, PERIODS
Discussion