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1201.

Two elements A and B combine to form a compound C by the transfer of electrons from A to B which of the following is (are) not true for C ?

Answer»

It has a high melting point
it has a LOW BOILING point
It CONDUCTS electricity.
It is a solid.

ANSWER :B
Discussion
1202.

Which of the following is a Doberiner's triad.

Answer»

NE, Ca, NA<BR>`H_2, N_2, O_2`
`Li, Na, K`
`Na, Br, Ar`

ANSWER :C
Discussion
1203.

What is Myopia? Name the lens used to correct Myopia.

Answer»

SOLUTION :Myopia (SHORT sightedness) is the INABILITY of an eye in viewing LONG distant objects.The Myopia is corrected by using a CONCAVE lens which diverges and shifts the image to the retina.
Discussion
1204.

When a metallic oxide is dissolved in water, then the solution formed has a high concentration of which ions

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`H^(+)`
`H_(3)O^(+)`
`OH^(-)`
`M^(+)`

ANSWER :C
Discussion
1205.

What is an indicator ?

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SOLUTION :An indicator is a SUBSTANCE that shows whether a GIVEN solution is acidic , BASIC or neutral.
Discussion
1206.

Which metal does not react with cold water, but reacts with hot water ?

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Solution : Magnesium does not REACT with cold WATER but it REACTS with hot water.
Discussion
1207.

Write the number of periods the modern periodic table has. State the changes in valency and metallic character of elements as we move from left to right in a period. Also state the changes, if any, in the valency and atomic size of elements as we move down a group.

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SOLUTION :No. of periods : 7.
Valency across a PERIOD increases from 1 to 4, then decreases from 4 to ZERO.
Metallic character of ELEMENTS across a period decreases.
Valency remains the same down a group
Atomic SIZE of elements increases down a group.
Discussion
1208.

What are coinage metals ?

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Solution :COPPER silver and GODL are called coinage METALS , as they are USED in making coinsand jewellery .
Discussion
1209.

The salts which make water hard are

Answer»

CALCIUM and MAGNESIUM sulphates
calcium and magnesium CHLORIDES
calcium and magnesium bicarbonates
any of the above

SOLUTION :any of the above
Discussion
1210.

What is Metathesis reaction?

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Solution :The ion of ONE compound is replaced by the ion of the another compound .IONS of IDENTICAL CHARGES are only intercharged ,i.e. a cation can be replaced by another cation.This reaction is called metathesis reaction.
Discussion
1211.

The third period contains only eight elements even though the electron capacity of the third shell is 18.

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Solution :(i) Period 3 of the periodic table consists of elementswhose atom has three she ll s occupied by electrons.
(ii)As pe r the electron HOLDING capacity of shells ,2 ELEMENTS are present in the first period, and8 elements in the second period.
(iii) The thi rd per io d also contain only eight elementsdue to the law of electron OCTET and also electronswill fill orbitals in increasing order of energy, i.e.the LOWEST energy orbital first.
Discussion
1212.

Which of the following is used as food preservator ?

Answer»

`CH_(3)OH`
`CH_(3)COOH`
`CH_(3)CHO`
`CH_(3)COCH_(3)`

Answer :B
Discussion
1213.

What is true about simple cubic type of unit cells?

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7 constituents are at different corners of the cube.
`Z_(EFF) = 1`.
CONTRIBUTION by one CORNER is `(1)//(2)` of an atom`.
None of the above.

Answer :B
Discussion
1214.

Which of the following hydroxides is not an alkali?

Answer»

AMMONIUM hydroxide
Calcium hydroxide
Copper hydroxide
Sodium hydroxide

Answer :C
Discussion
1215.

What is meant by heteroatom ? Give examples.

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Solution :In a hydrocarbon chain, the element replacing hydrogen is referred to as a HETEROATOM.
In a hydrocarbon chain, hydrogen atom/s can be replaced by HETEROATOMS, such that the valency of carbon remain satisfied.
Examples :
(1) Halogens LIKE chlorine, BROMINE.
(2) Oxygen, nitrogen and sulphur ELEMENTS.
Discussion
1216.

What characteristics of food containing oil and fat change when exposed to air for a long time ?

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SOLUTION :When food CONTAINING OIL and fat are exposed to air for a LONG time then its TASTE and smell get changed due to rancidity.
Discussion
1217.

The soap can be hardened by

Answer»

adding sodium CARBONATE or sodium silicate during its manufacture
adding sodium CHLORIDE
adding POTASSIUM hydroxide
adding animal fat and coconut oil

Answer :A
Discussion
1218.

Which electronic configuration corresponds to a noble gas?

Answer»

2, 2
` 2, 8, 2`
2, 8,5
`2, 8, 8`

SOLUTION :`2, 8, 8`
Discussion
1219.

Write the chemical name of Na_2CO_3. 10 H_2O and Na_2CO_3. Write the significance of 10 H_2O Mention the term used for water molecules attached with a salt. With the help of a chemical equation , explain the method of preparation of both Na_2CO_3. 10 H_2O and Na_2CO_3. Also list two uses of Na_2CO_3. 10 H_2O

Answer»

Solution :`Na_2CO_3. 10 H_2O`: Sodium carbonate DECAHYDRATE.
`Na_2CO_3`: Anhydrous sodium carbonate
`10 H_2O`: WATER of crystallization which impacts SHAPE and colour to the crystals.
Preparation:
`NaCl+H_2O+CO_2+NH_3to Nh_4Cl+NaHCO_3`
`2NaHCO_3 to^(Heat) Na_2CO_3+ H_2O+ CO_2`
`Na_2CO_3+ 10H_2O to Na_2CO_3. 10 H_2O`
USES:
(i) Used in GLASS, soap and paper industries.
(ii) Used in the manufacture of borax.
(iii) Used as a cleaning agent for domestic purpose.
Discussion
1220.

Which metal process low melting point ?

Answer»

GALLIUM
CESIUM
ALUMINIUM
COPPER

ANSWER :A
Discussion
1221.

What is colour of NO_2 gas?

Answer»

yellow
brown
red
violet

Answer :B
Discussion
1222.

What are antacids ? How pH change causes tooth decay ?

Answer»

Solution :Antacids are weak bases which NEUTRALIZE excess of acid and give RELIEF from pain. Antacids like MILK of magnesia and sodium bicarbonate are weak bases. Tooth DECAY starts when the PH of the mouth is lower than 5.5. Tooth enamel, the hardest substance of our body, gets corroded where the pH is below 5.5.
Tooth pastes are generally basic in nature and these neutralize the excess acid and prevent tooth decay.
Discussion
1223.

What happens when dilute hydrochloric acid is added to the following and write balanced chemical equations (i) Bleaching powder (ii) Zinc granules (iii) Baking soda

Answer»

Solution :(i) Calcium chloride and chlorine gas are formed.
`UNDERSET("POWDER")underset("Bleaching")(CaOCl_2(s))+2HCl(AQ)rarrunderset("chloride")underset("Calcium")(CaCl_(2)(s))+H_(2)O(l)+Cl_(2)(g)`
(ii) Hydrogen gas is evolved.
`underset("ZINC granucles")(Zn(s))+2HCl(aq)rarrunderset("chloride")underset("Zine")(ZnCl_(2)(aq))+H_(2)(g)`
(iii) Sodium chloride and carbon dioxide gas are formed.
`underset("Baking sada")(NaHCO_3(s))+HCl(aq) rarrunderset("chloride")underset("Sodium")(NaCl)(aq)+H_(2)O(l)+underset("dioxide")underset("Carbon")(CO_2(g))`
Discussion
1224.

Which elements has A total of three shells, with four electrons in its valence shell ?

Answer»

Solution :SILICON has four ELECTRONS in its VALENCE shell.
Discussion
1225.

Which of the following hydrocarbons undergo addition reaction ? C_2H_6, C_3H_8, C_3H_6, C_2H_2 and CH_4

Answer»

SOLUTION :UNSATURATED HYDROCARBONS `C_3H_6 and C_2H_2`.
Discussion
1226.

Which of the following represents 1 amu?

Answer»

Mass of a `C-12` atom
Mass of a HYDROGEN atom
`1//12^("th")` of the mass of `C-12` atom
Mass of `O-16` atom

Solution :Hint : By definition 1 amu is defined as precisely `1//12^("th")` the mass of an atom of CARBON - 12.
So, ANSWER (c ) is correct.
Discussion
1227.

What would be the electron-dot structure of a molecule of sulphur which is made up of eight atoms of sulphur?

Answer»

SOLUTION :
Discussion
1228.

What would be the electron dot structure of carbon dioxide which has the formula CO_(2)?

Answer»

SOLUTION :In carbon dioxide molecule, the two oxygen atoms are bonded on EITHER side with carbon atom by double bonds. Thus, there are 2 double bonds in `CO_(2)`.
Carbon shares its two electron in the formation of a double bond with one oxygen atom and another two electrons with another oxygen atom. In this process, both the oxygen atoms and the carbon atom acquire the stable ELECTRONIC CONFIGURATION of the noble gas NEON. The formation of`CO_(2)` molecule is shown below:

Valencies of C and O are 4 and 2 respectively.
Discussion
1229.

Which of the following are isomers?

Answer»

ETHANE and propane
ethane and ethene
ethene and ethyne
BUTANE and ISOBUTANE

Solution :butane and isobutane
Discussion
1230.

We oftenfindsmallpacketsofsilicagelin foodpacksleatherandelectronicgoods .Whatare hygroscopicsubstances ?

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SOLUTION :Certainsubstances, whenexposedtothe atmosphereat ordinarytemperatureabsorbmoisture withoutdissolvingit .Hygroscopicsubstancesdo NOTCHANGE itsstateon exposureto AIR .
Discussion
1231.

Which of the following molecules has maximum bond angle

Answer»

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

ANSWER :D
Discussion
1232.

When a piece of zinc is added to blue copper sulphate solution, the solution becomes

Answer»

orange
green
colourless
violet and then TURNS GREENS

ANSWER :C
Discussion
1233.

The vapour pressure of a solution is always less than of the pure solvent, when the temperature of both the solution and solvent are thesame, with thesame external pressure acting over them. Explain.

Answer»

Solution :(i) RELATION between thevapour PRESSURE of the liquid andits intermolecular forces of attraction
(ii) comparison of theconstituents of solution andpure solvent
(iii) comparison of the intermolecular force of attraction existing in the solution andthat in the existing pure solvent
(IV) EFFECT on vapour pressure
Discussion
1234.

Which element has a total of two shells and there are three electrons in its valence shell?

Answer»

Beryllium
BORON
ALUMINIUM
MAGNESIUM

SOLUTION :Boron
Discussion
1235.

Write an equation to show the reaction between Plaster of Paris and water.

Answer»

SOLUTION :`CaSO_4 1/2 H_2O+ 3/2 H_2O to CaSO_4. 2 H_2O`
(Plaster of PARIS) (Water) (Gypsum)
Discussion
1236.

What happens whencopper is treated with conc.HNO_(3) and with conc.H_(2)SO_(4)?

Answer»

Solution :`Cu+4HNO_(3)rightarrowCu(NO_(3))_(2)+2NOuparrow+2H_(2)O`
COPPER nitrate Nitrogen DIOXIDE
`Cu+2h_(2)SO_(4)RightarrowCuSO_(4)+SO_(2)uparrow+H_(2)O`
Copper sulphate
Discussion
1237.

Total number of sigma bonds involved in ethylene molecule C_(2)H_(4) are

Answer»

3
5
2
1

Solution :
TOTAL NUMBR of SIGMA BONDS =5
Discussion
1238.

What is the basis of the long form of the periodic table?

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ATOMIC mass
Atomic NUMBER
Atomic size
Metallic and NONMETALLIC character

Solution :Atomic number
Discussion
1239.

Which of the following reaction takes place between the reaction of alcohol and carboxylic aicd in the presence of concentrated H_(2)SO_(4) ?

Answer»

Hydrolysis
BETA ELIMINATION
SAPONIFICATION
Esterification

ANSWER :D
Discussion
1240.

Which of the following statement is correct and why Copper can displace silver from silver nitrate and silver can not displace copper from copper sulphate solution.

Answer»

SOLUTION :Copper is more reactive than SILVER. THEREFORE copper displaces silver from silver nitrate solution.
`Cu(s)+2AgNO_(3) to Cu(NO_(3))_(2)(AQ)+2Ag(s)`.
Discussion
1241.

Which of the following organic compounds will undergo addition reactions?(a) C_2H_6 (b) C_2H_2 (c) C_3H_8 (d) C_3H_6

Answer»

SOLUTION : Unsaturated ORGANIC compounds containing double or triple bond between C atoms UNDERGO addition reactions. Thus, `C_2H_2` and `C_3H_6` will undergo addition reactions.
Discussion
1242.

What are the ions in aqueous solutions?

Answer»

SOLUTION :HYDROGENAND HYDROXYL ION .
Discussion
1243.

What is the correct increasing order of the pH of the following solutions with equal concentrations?

Answer»

`HClltNaOHltCH_(3)COOH`
`HClltCH_(3)COOHltNaOH`
`NaOHltHClltCH_(3)COOH`
`CH_(3)COOHltNaOHltHCl`

ANSWER :B
Discussion
1244.

What type of particles compose a nonelectrolyte ?

Answer»

SOLUTION :Undissociated MOLECULES only
Discussion
1245.

While mixing H_2 SO_4 with water which of the following precautions should be taken?

Answer»

never ADD ACID to WATER
never add water to acid
add the lighter heavier LIQUID
AVOID sunlight

Solution :never add water to acid
Discussion
1246.

Write the names and structural formulae of the following:a saturated hydrocarbon

Answer»

SOLUTION :ETHANE` H-UNDERSET(H)underset(|) OVERSET(H) overset(|) C-underset(H) underset(|) overset(H) overset(|) C-H`
Discussion
1247.

Whatarenucleous ?

Answer»

Solution :Totalnumberof protonsandneutronspresentin THENUCLEUSOF anatomis KNOWNAS NUCLEOUS .
Discussion
1248.

Which of the following properties of atom could be explainedcorrectlyby Thomson model of atom?

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OVERALL NEUTRALITY of atom
Spectrum of HYDROGEN atom
Position of ELECTRONS, PROTONS and neutrons
Stability of atom

Answer :A
Discussion
1249.

Write the number of H atoms in a molecule of alkyne if the number of C atoms is four. What is the formula of this molecule?

Answer»

Solution :NUMBER of H atoms = 6, FORMULA = `C_4H_6`
Discussion
1250.

Which of the following compounds is not a hydrocarbon ?

Answer»

`R-CH_3`
`CH_2=CH_2`
`CH_3OH`
`CH_4`

ANSWER :C
Discussion