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1401.

The resistance of a conductor is 27Omega. If it is cut into three equal parts and connected in parallel, then its total resistance is

Answer»

`6OMEGA`
`3OMEGA`
`9OMEGA`
`27Omega`

ANSWER :B
Discussion
1402.

What is meant by soap? Mention the structure of molecule of soap.

Answer»

Solution :Soap is a sodium or potassium salt of long chain carboxylic acid (fatty acid).
Soap molecule consist of two parts: ONE part contains long hydrocarbon chain. It is hydrophobic END. It is also known as non-POLAR tail.
ANOTHER part is a negatively CHARGED polar part, which is known as polar head. It is hydrophilic end.
Discussion
1403.

What will be made the cathode ?

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SOLUTION :COPPER WARE
Discussion
1404.

What is mutation ?

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SOLUTION :Organisms have evolved in number of ways to protect their DNA from changes inspite of those MECHANISMS, howerver changes in the DNA sequence is CALLED a mution.
Discussion
1405.

What does one mean by exothermic and endothermic reactions? Give examples.

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Solution :Exothermic reaction: In exothermic reaction, HEAT is evolved during the reaction which is indicated by .+ heat sign on the right HAND side of the equation.
For example:
`CaO(s)+H_(2)O(L)rarrCa(OH)_(2)(aq)+"Heat"`
Endothermic reaction: In this reaction, heat is absorbed which is indicated by PUTTING .+ heat. sign on the left hand side of the equation.
For example:
`N_(2)(g)+O_(2)(g)+"Heat"rarr2NO(g)`
Discussion
1406.

Why are unsaturated hydrocarbons more reactive than saturated hydrocarbon?

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SOLUTION :Presence of DOUBLE and TRIPLE COVALENT bonds make these compounds more REACTIVE.
Discussion
1407.

Three elements with filled outermost shell .

Answer»

SOLUTION :(i) HELIUM (2) (ii) NEON (2 , 8) (iii) Krpton (2,8,18,8).
Discussion
1408.

Which one of the following is a general formula for alkyne?

Answer»

`C_(N)-H_(2N)`
`C_(n)H_(2n+2)`
`C_(n)H_(2n-2)`
`C_(n)H_(n)`

ANSWER :C
Discussion
1409.

Vapourdensity =_______.

Answer»

SOLUTION :`("MASSOF 1volumeof gasorvapourat STP")/( "Massofvolumeofhydrogen ")`
Discussion
1410.

Write the uses of ethanoic acid.

Answer»

Solution :The uses of ethanoic acid are as follows:
(1) In the preparation of vinegar, which is used to add sour taste to FOOD items.
(2) It is used as food preservator to preserve the food for long time.
(3) As a solvent and reagent in laboratory.
(4) It is used to prepare lead white (pigment).
Discussion
1411.

Which of the following is not a man made polymer ?

Answer»

NYLON
polyethen
TEFLON
WOOL

ANSWER :D
Discussion
1412.

Which is incorrect statement in the following?

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<P>Aqueous solution of an acid conduct ELECTRICITY.
The p in PH stand for power.
Our body works within the pH range 7.0 to 7.8.
Calcium sulphate Hemihydrate is known as Bleaching POWDER.

Solution :Calcium sulphate Hemihydrate is known as Bleaching powder.
Discussion
1413.

What is the nature of C to C bond in C_2H_4?

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SOLUTION : DOUBLE BOND (C=C)
Discussion
1414.

Which of these has a triple covalentbond?

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`PH_(3)`
`CO_(2)`
`AlCl_(3)`
`C_(2)H_(2)`

Solution :`C_(2)H_(2)` CONTAINS carbon-carbon triple bond.
`H-C-=C-H`
Discussion
1415.

What happens when (write balanced chemical equations only) Solutions of sodium sulphate and barium chloride are mixed.

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Solution :`Na_(2)SO_(4)(AQ)+BaCl_(2)(aq)toBaSO_(4)(s)+2NaCl(aq)`
Discussion
1416.

Which of the following compound has highest covalent character

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`LICL`
`LIBR`
`LIF`
`LII`

ANSWER :D
Discussion
1417.

Vinegar is a solution of

Answer»

50% - acetic acid in ALCOHOL
5% - acetic acid in alcohol
5% - 8% acetic acid in WATER
50%- 60% acetic acid in water

Answer :C
Discussion
1418.

What happens when hydrogen gas is passed through soap solution and the bubbles escaping water are ignited with a flame ?

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The gas burns silently.
The gas burns with a pop SOUND.
The gas gives a smell of burning sulphur.
The gas being HEAVIER does not ESCAPE the soap solution.

Solution :Hydrogen gas is combustible and burns with a pop sound.
Discussion
1419.

Write the example of decomposition reaction which occurs in nature.

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SOLUTION :Rottening of FRUITS and VEGETABLES
Discussion
1420.

To increase the pH value of a neutral solution we should add

Answer»

an ACID
an acid salt
an alkali
a salt

Answer :C
Discussion
1421.

Which parameter decreases as we move from left to right along a period?

Answer»

metallic CHARACTER
VALENCE electrons
electronegativity
ELECTRON shells

Answer :A
Discussion
1422.

The standard electrode potentials of the electodes are given below. Arrange them in decreasin order of ease of oxidations {:((1),"Electrode " - I"," E^(@) = - 2.89 V ),((2),"Electrode " - II"," E^(@) = - 0.16 V),((3),"Electrode " - III"," E^(@) = 0.77 V),((4),"Electrode " - IV"," E^(@) = - 2.93 V),((5),"Electrode " - V"," E^(@) = - 1.67 V):}

Answer»

3 2 5 1 4
4 1 5 2 3
3 5 1 4 2
3 2 1 4 5

Solution :The electrode with greater negative value of standard reduction potential acts as anode. The electrode with greater positive value of standard reduction potential acts as cathode. Oxidation takes placed at anode and reduction takes PLACE at cathode. X
(i) Electrode `- IV E^(@) = -2.93V`
(ii) Electrode `- I, E^(@) = -2.89 V`
(iii) Electrode `- V E^(@) = -1.67 V`
(iv) Electrode `- II, E^(@) = -0.16V`
(v) Electrode `- III E^(@) = 0.77 V`
Discussion
1423.

Which one of the following is most metallic?NaMgAlSi

Answer»

NA
Mg
Al
Si

Solution :Na
Discussion
1424.

Write the names and structural formulae of the following:an unsaturated hydrocarbon with a double bond

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SOLUTION :Ethane ` UNDERSET(H)underset(|) overset(H)overset(|) C= underset(H) underset(||) overset(H) overset(|)C`
Discussion
1425.

What happens when (give balanced equations):A mixture of ethene and hydrogen is passed over nickel at 159^@C

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SOLUTION :`CH_2= CH_2 + H - H to CH_3 - CH_3`
Discussion
1426.

Which metal reacts vigorously with dilute hydrochloric acid ?

Answer»

Solution :MAGNESIUM metal REACTS VIGOROUSLY with dilute hydrochloric acid.
Discussion
1427.

Write the type of chemical reaction in the following. rusting of iron

Answer»

SOLUTION :COMBINATION or OXIDATION REACTION.
Discussion
1428.

What is the color of Potassium Dichromate solution?

Answer»

Pink
Blue
Red
Orange

Answer :D
Discussion
1429.

There are two metallic wires of the same thickness made from iron and silver. If the length of iron wire is 12cm, what should be the length of silver wire which is equal to the resistance of iron wire? Data : Resistivity of iron= 10 xx 10^(-8) Omegam Resistivity of silver= 16 xx 10^(-8) Omega m

Answer»

Solution :`I_(i) = 12 CM `
`I_(s) =? `
` S_(i) = 10 xx 10^(-8) Omega m `
` S_(s) = 16 xx 10^(-8) Omega m`
` (S_i)/(S_(s) ) = (I_s)/(I_i) = (10 xx 10^(-8) )/(16 xx 10^(-8) ) = (I_((s)) )/(12) = 120/16 = I_((s)) `
`I_((s)) = 7.5 cm`
Discussion
1430.

Which of the following has more electrons than neutrons?

Answer»

`F^(-)`
`Al^(3+)`
`O^(2-)`
`Na^(+)`

Solution :`{:("ION","Electrons","NEUTRONS"),(F^(-),10,10),(Al^(3+),10,14),(O^(2-),10,8),(Na^(+),10,11):}`
Discussion
1431.

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

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SOLUTION :A reaction which has an EQUAL number of atoms of all the ELEMENTS on both SIDES of the chemical equation is called a balanced chemical equation. Chemical reaction should be balanced to follow law of conservation of mass.( The total mass of the elements of the reactants has to be equal to the total mass of products )
Discussion
1432.

Write two reasons responsible for the late discovery of noble gases.

Answer»

Solution :(i) Most of the noble gas elements are not present in earth crust as minerals LIKE other elements and are present in AIR to a very small EXTENT.
(ii) Their atoms have stable electronic configuration of their outermost shells also called VALENCE shells. (2 in case of He and 8 for other elements). They donot combine with atoms of other elements and donot exist independently. That is why noble gas elements were DISCOVERED at a later stage.
Discussion
1433.

Which of the following are present in a dilute aqueous solution of hydrochloric acid ?

Answer»

`H_(3)O^(+)+Cl^(-)`
`H_(3)O^(+)+OH^(-)`
`Cl^(-) +OH^(-)`
UNIONISED HCl

Solution :Hydrochloric acid ionises as FOLLOWS:
`HCl rarr H^(+) + Cl^(-)`
`H^(+)` ions combine with water MOLECULES to FORM `H_(3)O^(+)` . THEREFORE, the ions present in dilute aqueous solution of hydrochloric acid are `H_(3)O^(+)` and `Cl^(-)`
Discussion
1434.

Which of the following metals do react with dilute HNO_(3)with the liberation of hydrogen gas ?

Answer»

Ca
Mg
Fe
Mn

ANSWER :B::D
Discussion
1435.

Turmeric turns _____ in basic medium.

Answer»

SOLUTION :DEEP BROWN
Discussion
1436.

What are isotones ? Give example.

Answer»

SOLUTION :Atoms of different elements having the same number of neutrons but different atomic number and different MASS NUMBERS are called isotones. e.g., `""_(6)C^(13),""_(7)N^(14),`
Discussion
1437.

What is the nature of metal oxides?

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SOLUTION :METAL OXIDES are BASIC in NATURE.
Discussion
1438.

Which of the following molecule has net dipole moment?

Answer»

`CO_(2)`
`H_(2)O`
`BF_(3)`
`CH_(4)`

Answer :B
Discussion
1439.

Use Mendeleev's Periodic Table to predict the formulae for the oxides of the following elements : K, C, AI, Si, Ba.

Answer»

Solution :`K_(2) O, CO_(2), SiO_(2), BAO`.
Discussion
1440.

What is meant by water of crystallization. How many molecules of water are present in hydrated copper sulphate? Write its formula. What colour change do you observe when it is heated?

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SOLUTION :Water ofcrystallization is the FIXED NUMBER of water molecules present in one formula unit of salt.
(i) Five molecules of water.
(II) Formula: `CuSO_4. 5H_2O`
(ii) When heated its colour changes from blue to WHITE.
Discussion
1441.

When iron nail is dipped in a solution of copper sulphate, then, the colour of the solution becomes ……….after sometime.

Answer»

SOLUTION :PALE GREEN
Discussion
1442.

What is a homologous series of carbon compounds?

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Solution :A homologous series is the family of organic COMPOUND having the same functional GROUN and the sucessive (adjacent) members of which DIFFER by `CH_(2)` UNIT or 14 mass unit.
Discussion
1443.

What is neutralisation reaction ? Give two examples of such type of reactions.

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SOLUTION :All bases react wiil acids to form salt and water . Such TYPE of reactions are called neutralisation reactions .
`underset(("Base"))underset("Sodium hydroxide")(NaOH)+underset(("Acid"))underset("Hydrochloric acid")(HCl)rarrunderset(("Salt"))underset("Sodium chloride")(NaCl)+underset("Water")(H_2O)`
`underset(("Base"))underset("Potassium hydroxide")(KOH)+underset(("Acid"))underset("Nitric acid")(HNO_(3))rarrunderset(("Salt"))underset("Potassium nitrate")(KNO_3)+underset("Water")(H_2O)`
Discussion
1444.

Write the balanced chemical equation for the following reactions. Barium chloride + potassium sulphate to barium sulphate + potassium chloride.

Answer»

SOLUTION :`BaCl_2+K_2SO_4toBaSO_4+2KCl`
Discussion
1445.

Why are the values of electron affinity of the IIA group and IIB group elements less than ero?

Answer»

Solution :Electronic configuration of II A and II B group
elements is `ns^(2)np^(0)`. ADDITION of an electron to these
elements requires energy to overcome repulsive
forces between completely filled ns electrons and
electron GOING to be added. Hence, electron affinity
VALUES are less than zero.
Discussion
1446.

What is gangue and what is concentration?

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SOLUTION :Ore are usualy associated with unwanted earthly matter called gangue ( SAND, clay etc) and the removal of this unwanted impurities is called concentration. The ganguae has to be REMOVED before the EXTRACTION of METALS.
Discussion
1447.

What is the role of moisture in rusting of iron ?

Answer»

Solution :(i) Formation of IRON (II) hydroxide
(ii) Composition of rust.
(III) Comparison of form in which iron is present in PURE metal and rust.
(iv) Change undergone by iron during the rusting process.
(V) Requisite for an ELECTROCHEMICAL cell.
(vi) Identification of electrode and electrolyte in the prcoess of rusting
Discussion
1448.

What type of mixture is produced when acetic acid is mixed with water?

Answer»

SOLUTION :HOMOGENEOUS.
Discussion
1449.

Which of the following is a strong acid?

Answer»

`H_(2)CO_(3)`
`CH_(3)COOH`
`HCl`
`HCOOH`

Solution :NA
Discussion
1450.

Think about it, What is the periodic trend in the variation of valency while going from left to right within a period. Explain the answer with reference to period 2 and period 3:

Answer»

Solution :
For PERIODS 2 and 3, on going from LEFT to right, the valency increases from 1 to 4, then starts decreasing upto 0.
Discussion