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11951.

Which of the ores mentioned in a table can be concentrated by magnetic separation method ?

Answer»

Solution :If EITHER ORE or gangue is attracted towards MAGNETIC field, then ore can be concentrated by magnetic separation method.

For example : Haematite, Magnetite, Siderite and Iron PYRITES.
Discussion
11952.

When the emf of the cell is determined under standard conditions, it is called as _______

Answer»

SINGLE ELECTRODE emf
standard emf
individual emf
half CELL emf

Answer :B
Discussion
11953.

Total number of isomeric ketones can be calculated by formula

Answer»

`I = 2^(N-3) - 1`
`I = 2^(n-2)`
`I = 2^(n-2) - 1`
`I = 2^(n)`

ANSWER :A
Discussion
11954.

Which of the following is/are examples of pseudo unimolecular reactions?

Answer»

`CH_(3)CO_(2)C_(2)H_(5)+H_(2)Ooverset(H^(+))(to)CH_(3)CO_(2)H+C_(2)H_(5)OH`
`C_(12)H_(22)O_(11)+H_(2)Ooverset(H^(+))(to)underset("glucose fructose")(C_(6)H_(12)O_(6)+C_(6)H_(12)O_(6))`
`SO_(2)Cl_(2)toSO_(2)+Cl_(2)`
`CH_(3)CO_(2)C_(2)H_(5)+H_(3)Ooverset(OH^(-))(to)CH_(3)CO_(2)H_C_(2)H_(5)OH`

Solution :`A,BTO` pseudo UNI molecular reactions
Discussion
11955.

Which of the following compounds will give yellow precipitate on warming with a solution of iodine and aqueous alkali?

Answer»

`CH_(3)CH_(2)CH_(2)CH_(2)OH`
`CH_(3)CHOHCH_(2)CH_(3)`
`(CH_(3))_(3)COH`
`CH_(3)CH_(2)OCH_(2)CH_(3)`

Solution :Only `CH_(3)CH_(2)CHOHCH_(3)`: contains the grouping `CH_(3)CHOH` - and hence GIVES iodoform TEST.
Discussion
11956.

Which of the following element does not show an oxidation state of +4 ?

Answer»

OXYGEN
SULPHUR
SELENIUM
TELLURIUM

ANSWER :A
Discussion
11957.

Which of the following characteristics of transition metals is associated with its catalytic activity?

Answer»

HIGH IONISATION energy
variable oxidation state
high effective nuclear charge
all of these

Answer :B
Discussion
11958.

Which of the following amines will not react with HNO_2 acid to give nitrogen :

Answer»

`CH_3NH_2`
`CH_3CH_2NH_2`

ANSWER :D
Discussion
11959.

What is the effect of temperature on the electrical conductance of metal ?

Answer»

SOLUTION :Temperature increases, electrical conductance DECREASES.
Discussion
11960.

Which statements about mercury are correct?

Answer»

HG is a liquid metal
Hg forms two series of salts
Hg forms no AMALGAM with IRON and platinum
Hg does not show VARIABLE valency

Answer :A::B::C::D
Discussion
11961.

Write the mechanism of acid dehydration of ethanol to yield ethene.

Answer»

SOLUTION :The MECHANISM is EXPLAINED as under :
Discussion
11962.

Which of the following anion is a strongest base ?

Answer»

`C_(6) H_(5) COO^(-)`
`HCOO^(-)`
`CH_(3) COO^(-)`
`(CH_(3))_(2) CHCOO`

ANSWER :D
Discussion
11963.

Which one of the following is more acidic?

Answer»

Benzyl alcohol
Phenol
ETHANOL
METHANOL

SOLUTION :Phenol
Discussion
11964.

Which is the least polarisable among all the noble gases?

Answer»

He
Xe
Ar
Ne

Answer :A
Discussion
11965.

What is chemical volcano ?

Answer»

Solution :On HEATING crystals or red coloured ammoninum dichromate a violent action accompanied by flashes of light and evoluction of nitrogen takes place, LEAVING behind green coloured chromimum sesquioxide.
`(NH_4)_2Cr_2O_7 OVERSET(DELTA) rarr N_2 + 4H_2O +Cr_2O_3`
Discussion
11966.

Which one of the following objects is 'achiral'

Answer»

Letter P
Letter F
Ball
A pair of HAND

Solution :Ball is achiral where other objects are CHIRAL because objects and their MIRROR images are non-super imposable.
Discussion
11967.

Which of the following transformations are correct in acidic medium ?

Answer»




ANSWER :D
Discussion
11968.

Which of the following does not have zero entropy even at absolute zer0o? CO,CO_(2),NaCl,NO

Answer»

`CO,CO_(2)`
`CO,NO`
`CO_(2),NaCl`
`NaCl`

Solution :CO and NO molcules in solid STATES at 0 K adopt a nearly RANDOM arrangement INDICATING a positive value of entropy. It is DUE to their dipole ment which result in disorder.
Discussion
11969.

Which of the following compouds will have the highest melting point and why?

Answer»

SOLUTION :The compound (II) will have the highest melting point because out of the three compounds, it is maximum SYMMETRICAL and this will LEAD to maximum CLOSE PACKING in the solid state and hence highest melting point.
Discussion
11970.

Which of the following alkanes cannot be prepared by the Wurtz reaction in good yield ? (iv) CH_3CH_2C(CH_3)_2CH_2CH_3

Answer»

Solution : are THREE unsymmertical alkanes. So, these cannot be PREPARED by Wurtz REACTION in good YIELD.
Discussion
11971.

Write Nernst equation to calculate the cell potential of Mg(s)|Mg^(2+)(aq)||Ag^(+)(aq)|Ag

Answer»

Solution :The cell REACTION is `MG(s)+2AG^(2+)(AQ)toMg^(2+)(aq)+2Ag(s),n=2`
`therefore` Nernst equation is `E_(cell)=E_(cell)^(@)-2.303(RT)/(2F)"log"([Mg^(2+)])/([Ag^(+)]^(2))`
Discussion
11972.

X=number of compound obtained by aldol reaction Y=Number of compounds react with NaHCO_(3) Sum of X+Y is

Answer»


Solution :X=5(B,D,G,H,J) (`BETA`-HYDROXY carbonyl is aldol product).
Y=1 (I) (STRONGER acid than `H_(2)CO_(3)`)
Discussion
11973.

Write the isomers of the compound having formula C_(4)H_(9)Br

Answer»

Solution :(i) `CH(3)-CH_(2)-CH_(2)-CH_(2)Br":""1-Bromobutane"`
(ii) `CH_(3)-underset(Br)underset(|)CH-CH_(2)-CH_(3)":""2-Bromobutane"`
2-Bromobutane SHOWS optical isomerism. One of them is DEXTRO or d-form and the other is LAEVO or L- form.

(iii) `CH_(3)-underset(CH_(3))underset(|)CH-CH_(2)Br":""1-Bromo-2-methylpropane"`
(iv) `underset("2-Chloro-2-methylbutane")(CH_(3)-underset(CH_(3))underset(|)overset(CH_(3))overset(|)C-Br)":""2-Chloro-2-methylbutane"`
Discussion
11974.

What is flux ? Nameanacidflux.

Answer»

Solution :FLUX is asubstancethat combineswithgangue (earthlyimpurities) which may still be presentintheroastedor thecalcinedore to forman easilyfusiblematerialcalledtheslag. Forexample,
(i) Intheblastfurnace in themetallurgyof iron, CaO actsas THEBASIC flux. It removesthe acitic IMPURITY of`SiO_2 ` presentin theore toform fusiblecalciumsilicate slag
` underset ("Basic flux")(CaO(s))+underset ("Acidic impurity")(SiO_2(s)) overset (1123 K)toCaSiO_3(slag) `
(ii) Copperisextractedfromcopperpyrites. Roastingof COPPER pyrites mainlygives ` Cu_2 S and FeO`. Toremovebasic FeO, silica`(SiO_2) `is usedas theacidicflux whichcombines withFeO to formfusicles ferrous silicateslag.
`underset ("Basic impurity")(FeO) +underset ("Acidic flux")(SiO_2) tounderset ("Ferrous silicate (slag)")(FeSiO_3) `
Discussion
11975.

(W) and (X) are optically active isomers of C_(5) H_(9) Cl (W) on treatment with 1 mol of H_(2) is converted to an optically inactive compound(Y), but (X) gives an opticallyactgive compound (Z)under the sameconditions. Give the sturcture of (Y) and theconfigurations of (W),(X) and (Z) in Fischer projections.

Answer»

SOLUTION :
Discussion
11976.

Which is least thermally stable ?

Answer»

`Li_2 CO_3`
`Na_2 CO_3`
`K_2 CO_3`
`Rb_2 CO_3`

ANSWER :A
Discussion
11977.

The weight of a molecule of the compound C_(60)H_(122) is

Answer»

`1.4xx10^(-21)g`
`1.09xx10^(-21)g`
`5.025xx10^(23)g`
`16.023xx10^(23)g`

Solution :1 mole of `C_(60)H_(122)=60xx12+122xx1g=842 g`
`=6.023xx10^(23)` molecules
Weighta of 1 MOLECULE = `842/(6.023xx10^(23))g`
`=139.8xx10^(-23)=1.398xx10^(-21)=1.4xx10^(-21)g`
Discussion
11978.

Which of the following compounds when dissolved in water, gives a solution with pH less than seven ?

Answer»

`CH_(3)COCH_(3)`
`C_(8)H_(5)OH`
`C_(6)H_(5)NH_(2)`
`C_(2)H_(5)OH`

Answer :B
Discussion
11979.

Which of the following quantities is not a state function ?

Answer»

Temperature
Entropy
Enthalpy
Work.

Answer :D
Discussion
11980.

Which of the follwing represents the correct order of electeon affinities ?

Answer»

CL GT BR gt I gt F
Cl gt F LT Br lt I
F gt Cl gt Br gt I
Cl gt F gt Br gt I

Answer :D
Discussion
11981.

Write mechanism of Aldol addition reaction.

Answer»

Solution :MECHANISM of Aldol addition reaction :
step I : Base `(-OH^(-))` abstracts a hydrogen atom from `alpha`-carbon of aldehyde to from carbanion. In this step hydrogen GIVING the reactive enolate.

Step II : The nucleophilic enolate attacks the aldehyde at the electrophilic CARBONYL C in a nucleophilic addition type process giving an intermediate alkoxide

Step III : Alkoxide ion abstracts a hydrogen ion from WATER to from `beta`- hydroxy aldehyde. Base `OH^(-)` ion is regenerated
Discussion
11982.

Which reagent would enable you to remove SO_4^(2-)ions from solution containing both SO_4^(2-) and Cl^-ions?

Answer»

NaOH
`PB^(2+)`
`Ba(OH)_2`
`BaSO_4`

ANSWER :C
Discussion
11983.

Which of the following statements is true in the case of physical adsorption of gases on solids

Answer»

It is exothermic process
It depends on the EASE of liquification of the GAS
It DECREASES with increase in temperature
All the above

Answer :D
Discussion
11984.

Which of the following FCC structure contains cations in alternate tetrahedral voids?

Answer»

NACL
ZnS
`Na_(2)O`
`CaF_(2)`

ANSWER :B
Discussion
11985.

Which of thefollowing compounds will notundergo aldol condensation

Answer»

ETHANAL
PROPANAL
2,2, tricholoroethanal
2,2 diboromoethania

ANSWER :C
Discussion
11986.

Which of the following compound is the strongest base?

Answer»




ANSWER :D
Discussion
11987.

When Cu metal is heated with concentrated sulphuric acid, then..........is obtained.

Answer»

`SO_(3)`
`H_(2)S`
`SO_(2)`
`O_(2)`

ANSWER :C
Discussion
11988.

Which of the following does not occur when the scawage is discharged into water ?

Answer»

INCREASE in `O_(2)`
Cyanophycean BLOOMS OCCUR
DEPLETION of `O_2` layers
Eutrophication

Answer :A
Discussion
11989.

Write the products formed when benzaldehde reacts with the following reagents: (i) CH_3CHO is presence of dilute NaOH (ii) (iii) Conc.NaOH (b) Distinguish between the following: (i) CH_3-CH=CH-CO-CH_3 andCH_3-CH_2-CO-CH=CH_2 (ii) Benzaldehyde and Benzoic acid.

Answer»

Solution :(a) (i) `C_6H_5 -overset(OH)overset|CH-CH_2CHO`
(II)
(iii) `C_6H_5CH_2OH and C_6H_5COONa`
Benzyl alcohol Sodium BENZOATE
(b) (i) `CH_3-CH=CH-CO-CH_3` gives a yellow precipitate of `CHI_3` when treated with `I_2` and NaOH solution as it is a methyl ketone.
`CH_3-CH_2-CO-CH=CH_2` does not give the TEST.
(ii) 2,4-DNP test: BENZALDEHYDE gives a yellow ppt. with 2,4-DNP solution.
Benzoic acid does not give the test.
Discussion
11990.

Which of the following statement (s) is (are) correct for the extractive metallurgy of aluminium ? (1) Red bauxite contains the impurities of iron oxides SiO_(2) and TiO_(2) (2) Red bauxite is purified by hall's and Serpeck's process (3) Hall - Heroult process is used for the electrolytic reduction of molten alumina dissolved in molten cryolite (4) In electrolytic reduction of alumina fluorine gas is liberated at anode as by product

Answer»

1, 2
1, 3
1, 4
3, 4

Answer :B
Discussion
11991.

Which of the following is not true about SO_(2)

Answer»

It decolourise `KMnO _(4)//H^(+)`
Liquid `SO _(2)` is a NON AQUEOUS solvent
It is a inear molecule
It can ACT like a preservative

Answer :C
Discussion
11992.

Which of the following statements is not true about glucose?

Answer»

It is an ALDOHEXOSE
On heating with Hl, it FORMS n-hexane
It is present in furanose form
It does not GIVE 2,4-DNP test

Answer :C
Discussion
11993.

Which of the following does not undergo polymerisation :

Answer»

`CH_3CHO`
HCHO
`CH_3COCH_3`
NONE

ANSWER :C
Discussion
11994.

Whatdoyoumean by peptidelinkage ?

Answer»

Solution :thelinkage`- overset(O ) overset(||) C-overset(H ) overset(|)N-`PRESENTIN peptides andproteinsis calledpeptidelinkage.
Discussion
11995.

The well known urinary antiseptic urotropine is formed when formaldehyde reacts with

Answer»

`NH_(2)OH`
`NH_(3)`
`NH_(2)NH_(2)`
`C_(6)H_(5)NHNH_(2)`.

SOLUTION :Formaldehyde reacts with `NH_(3)` to forin the well known urinary antiseptic urotropine, i.e., hexamethylenetetraamine, `(CH_(2))_(6)N_(4)`.
Discussion
11996.

What is ferromagnestism ? Iron (Z = 26) is strongly ferromagnetic. Explain.

Answer»

Solution :The substance containing large number of ELECTRONS can be permanently MAGNETISED, this property is CALLED as derromagnetism.
`._(26)FE = [Ar] 3d^(6) 4 s^(2)`
Iron consists of four unpaired electrons, HENCE it is strongly ferromagnetic.
Discussion
11997.

Which components are present in nucleotide ?

Answer»

Organic SUGAR
BASE contain nitrogen
Phosphoric acid
All of these

SOLUTION :All of these
Discussion
11998.

What type of isomerism is shown by the complex [Co(NH_(3))_(5)(SCN)]^(2+) ?

Answer»

SOLUTION :`[CO(NH_(3))_(5)(SCN)]^(2+)` SHOWS LINKAGE isomerism. Its linkage isomer is `[Co(NH_(3))_(5)(CNS)]^(2+)`.
Discussion
11999.

Which substance can be used in the preparation of marking ink?

Answer»

`AG`
`AgNO_3`
`AgBr`
`PbCO_3.Ph(OH)_2`

Answer :B
Discussion
12000.

When acetone is heated with ammonia gives diacetone amine, the intermediate compound gormed in this reaction is ,

Answer»

`(CH_(3))_(2) C = CHCOCH_(3)`
`CH_(3)CH_(2) CH = CH_(2)COCH_(3)`
`(CH_(3))_(2)C = CHCH_(2)CHO`
`(CH_(3))_(2) C = CH_(2)CH_(2)COCH_(3)`

SOLUTION :`(CH_(3))_(2) C = O + H_(2) CHCOCH_(3) overset(NH_(3)) to (CH_(3))_(2)C = CHCOCH_(3) + H_(2)O`
Discussion