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6301.

Write the ehemical reactions lnvolved in the proecess of extraction of Gold. Explain the role of dilute NaCN and Zn in this proeess

Answer»

Solution :`4Au(s)+8CN^(-) (AQ) +2H_2 O (aq)+O_2(g) to 4[AU(CN)_2]^(-) (aq)+4OH^(-) (aq)`
`2[Au(CN)_2]^(-) (aq)+Zn(s) to 2Au(s)+ [Zn(CN)_4]^(2-)` (aq)NaCN LEACHES gold/NaCN acts as a leacing agent / complexingagent Zn acts as reducing agent / Zn DISPLACES gold
Discussion
6302.

What type of ore are roasted?

Answer»

SOLUTION :SULPHIDE ORES are roasted to CONVERT them into their oxides.
Discussion
6303.

Which of the following compounds are enantiomers ?

Answer»




ANSWER :A
Discussion
6304.

Vitamin 'C' is a vitamin found in fruits and vegetables. It cannot be stored in our body. Why ?

Answer»

SOLUTION :It is SOLUBLE in water and hence EXCESS of it is READILY EXCRETED in urine.
Discussion
6305.

What is meant by the colloidal state of matter? Explain the following terms: (i) Multimolecular colloids (ii) electro-dialysis

Answer»


Answer :(i) Multimolecular colloids: In this TYPE, the PARTICLES consist of an aggregate of atoms or small molecules size less than `1` nm. For example, sols of god atoms and sulphur `(S_(8))` molecules. In these colloids, the particles are held together by van DER Waal's forces.
(ii) Movement of ions across the membrane can be expedited by applying electric potential through two ELECTRODES as SHOWN in fig. This method is faster than simple dialysis and is known as Electrodialysis.
`(##RES_PHY_CHM_XII_V02_C03_E01_267_A01##)`
Discussion
6306.

Which of the following is /are the method (s) of determining the molecular mass ?

Answer»

Using Henry's LAW
Using Raoult's law
Osmotic pressure MEASUREMENT METHOD
Both (B) and (C )

ANSWER :D
Discussion
6307.

The solubility of a compound MX_(2) at 25^(@)C is 5.0xx10^(-3) mol/L. Its solubility product at that temperature is :

Answer»

`25xx10^(-6)`
`5.0xx10^(-11)`
`5.0xx10^(-7)`
`1.25xx10^(-9)`

Solution :`MX_(2)hArr M^(2+)+2X^(-)`
`K_(SP)=(x)(2x)^(2)=4x^(3)`
`=4xx(5.0xx10^(-3))^(3)`
`=5.0xx10^(-7)`
Discussion
6308.

Which one gives only one monosubstitution product on chlorination

Answer»

n pentane
N Pentane
Isopentane
n butane

Solution : `CH_3-undersetunderset(CH_3)(|)oversetoverset(CH_3)(|)C-CH_3`
REPLACEABLE hydrogen atomsare present only on 4 primary carbon ATOMS. Hence, it GIVE only one MONOCHLORO Substituted prouduct.
Discussion
6309.

Which of the following combination does not liberated NH_(3) gas?

Answer»

HEATING of `NH_4ClO_4`
Heating of `NH_4Cl`
`(NH_4)_2CO_3+NaOH`
`Li_3N+H_2O`

ANSWER :A
Discussion
6310.

Which has maximum boiling point ?

Answer»

Kr
Xe
He
Ne

Solution :Xe has the maximum boiling point because of its maximum size and ALSO maximum VAN der WAALS FORCES of ATTRACTION.
Discussion
6311.

Which of the following is a homopolymer ?

Answer»

BAKELITE
Nylon 6,6
NEOPRENE
Buna-S

Solution :Neoprene is made up of SINGLE monomerspecies i.e., chloroprene .
Discussion
6312.

Which site of an enzyme is called allsteric site ?

Answer»

Solution :Sites DIFFERENT from active SITE of enzyme where a molecule can BIND and change the SHAPE of the active site iscalled allosteric site.
Discussion
6313.

Which additive is used during vulcanization, to accelarate rate of reaction ?

Answer»

ZNO
MGO
CaO
Bao

SOLUTION :ZnO
Discussion
6314.

What ishydroformylationof olefins ?

Answer»

SOLUTION :
Discussion
6315.

When sodium burns in excess of air, the compound formed is :

Answer»

SODIUM SUBOXIDE
Sodium peroxide
Sodium oxide
Sodium superoxide

Answer :B
Discussion
6316.

The reagent used to convert ethane 1,2-diol to ethanal is ………………………. .

Answer»

SOLUTION :DIL. `H_2SO_4` (or) ANHYDROUS `ZnCl_2`
Discussion
6317.

Which among the following metals crystallise as a simple cube?

Answer»

POLONIUM
IRON
COPPER
GOLD

SOLUTION :Polonium
Discussion
6318.

Which of the following is a lewis base ?

Answer»

`ALCl_3`
AG
`Ag(OH)_3`
`NH_3`

ANSWER :D
Discussion
6319.

Which of the following pairs of lons cannot be separated by H_2S in ammoniacal medium?

Answer»

`ZN^(2+)`, `NI^(2+)`
`Zn^(2+)Mg^(2+)`
 `Mn^(2+), Ca^(2+)`
`CO^(2+),Ca^(2+)`,

ANSWER :A
Discussion
6320.

Which of the following is false for normal hydrogen electrode ?

Answer»

the temperature is 298 K
the concentration of `H^(+)` ions in its solution is 1 M
the hydrogen gas PRESSURE is 2 atmospheres
an electrode to Pt , coated with platinum black is used

Solution :In NHE the hydrogen gas at 1 ATM pressure is used .
Discussion
6321.

Which one of the following salt is least soluble in water?

Answer»

`[MX(K_sp = 10^-18)]`
`[MY(K_sp = 10^-20)]`
`[MZ(K_sp = 10^-70)]`
All are EQUALLY soluble

Answer :2
Discussion
6322.

Which of the following dioxide of group 14 elements is not solid ?

Answer»

`SnO_(2)`
`GeO_(2)`
`SiO_(2)`
`CO_(2)`.

Solution :`CO_(2)` is gas.
Discussion
6323.

Vapour density of a gas is 32. Find the volume of 0.64g gas at27^@ C and 684 mm pressure .

Answer»


ANSWER :273.3 ML
Discussion
6324.

Which of the following is/are inner orbital complex as well as dimagnetic in nature : [Atomic no. toCr=24, Mn=25, Fe=26, Co=27]

Answer»

`[Zn(NH_(3))_(6)]^(2+)`
`[NI(NH_(3))_(6)]^(2+)`
`[Cr(NH_(3))_(6)]^(3+)`
`[CO(NH_(3))_(6)]^(3+)`

SOLUTION :In `[Co(NH_(3))_(6)]^(3+)`

INNER ORBITAL, dimagnetic nature
Discussion
6325.

Which of the following species contain only sigma bond?

Answer»

`SiCl_4`
`NO_3^-`
`HCN`
`SO_3^(2-) `

ANSWER :A
Discussion
6326.

Which of the following is not an example of phytohormones ?

Answer»

CYTOKININS 
ETHYLENE 
AUXINS 
Insulin

Answer :D
Discussion
6327.

Which of the following has minimum solubility product ?

Answer»

`NH_4Cl`
`CaCl_2`
`AGCL`
`AlCl_3`.

ANSWER :C
Discussion
6328.

Which of the following compounds on hydrolysis produces a compound which can react with semi-carbazide, reduce Tollen's reagent and can also give positive idoform test?

Answer»




ANSWER :B
Discussion
6329.

Which of thefollowing enzyme can hydrolyse the cellulose ?

Answer»

INVERTASE
Glycosidase
ZYMASE
DIASTASE

ANSWER :B
Discussion
6330.

Which of the following are diamagnetic in vapour state( A) Sodium metal (B) Sodium cations (C) Magnesium metal (D) Magnesium cations

Answer»

a and B are correct
C and d are correct
b,c and d are correct
a,c and d are correct

ANSWER :C
Discussion
6331.

which of the following atoms has the heighest first ionisation energy?

Answer»

Na
K
Sc
Rb

Answer :C
Discussion
6332.

The volume of ethyl alcohol (density 1.15 g/cc) that has to be added to prepare 100 cc of 0.5 M ethyl alcohol solution in water is

Answer»

1.15 CC
2 cc
2.15 cc
2.30 cc

Solution :100 cc of 0.5 M ethyl alcohol
`-= 100 XX 0.5 xx 10^(-3)` mole `=5 xx 10^(-2)` mole
`therefore` Weight of ethyl alcohol required
`=5 xx 10^(-2) xx 46 g = 2.3 g` [`therefore` Molecular weight of ethyl alcohol = 46]
`therefore d=("Mass")/("VOLUME") RARR 1.15 = 2.3/V rArr V = 2.30/1.15` =2
`therefore` Volume required=2cc
Discussion
6333.

Which one of the following is used to regenerate permutit in softening of hard water?

Answer»

COMMON SALT
BAKING SODA
WASHING soda
Quick lime

Solution :Common salt
Discussion
6334.

The substance which reacts with gangue to form fusible mineral is called _________

Answer»

Slag
Ore
FLUX
CATALYST

Answer :C
Discussion
6335.

Which of the following is NOT a voltaic cell ?

Answer»

CELL USED for metal PLATING
LEAD storage cell
Fuel cell
NICAD

Answer :A
Discussion
6336.

Which of the following acts as an antiseptic as well as disinfectant ?

Answer»

Equanil
Bithional
Phenol
Chlorine.

Answer :C
Discussion
6337.

Which one of the following ore is best concentrated by froth floatation method?

Answer»

Magnetite
Malachite
Galena
Haematite

Answer :C
Discussion
6338.

Which of the following is dihydric alcohol

Answer»

Glycerol
Ethylene glycol
Catechol
Resorcinol

Solution :Glycols are dihydric alcohols (having two hydroxyl GROUPS). Ethylene glycol is the FIRST membrane of this series.
`UNDERSET("Ethylene glycol"){:(CH_(2)OH),(|),(CH_(2)OH):}`
Discussion
6339.

Whichis strongerreducingagent Cr^(2+) orFe^(2+) ?

Answer»

Solution :When`CR^(2+)` and `Fe^(2+)`ACT asreducingagent`Cr^(2+) to Cr^(3+), Fe^(2+)to Fe^(3+)`
The`E_(cr^(3+) // Cr^(2+))^(0) ` valueis `-0.41 V` and `E_(Fe^(3+)//Fe^(3+))^(0)`
is +0.77V thismeansthat `Cr^(2+)`can beeasilyoxidizedto `Cr^(3+)` . But `Fe^(2+)`does not get oxidizedto `Fe^(3+)`easily . Therefore `Ce^(2+)`is abetterreducingagentthan `Fe^(3+)`
Discussion
6340.

The value of amu is equal to

Answer»

`1.57xx10^(-24)` kg
`1.66xx10^(-24)` kg
`1.99xx10^(-23)` kg
`1.66xx10^(-27)` kg

Solution :AMU represents ATOMIC mass unit. It is used in place of unified mass unit.
1 amu = 1 avogram =1 aston = 1 dalton
1 amu `=1/12 xx` mass =1 aston = 1 dalton
`=1/12xx1.9924xx10^(-23) G`
`=1.66 xx10^(-24) g=1.66xx10^(-27) kg`.
Discussion
6341.

What type of Isomerism is exhibited by different pairs of amines in molecular formula C4H11N.

Answer»

Solution :Position isomers : 1AND 2, 5 and 6, 3and 4
Chain isomers: 1 and 3, 2 and 3, 1 and 4, 2AND 4
Metamers : 5 and 7, 6 and 7
FUNCTIONAL isomers : All `1^@` amines are functional isomers of `2^@` and `3^@` amines and vice versa
Discussion
6342.

Which is a stronger acid - phenol or cresol ? Explain.

Answer»

SOLUTION :PHENOL is stronger than cresol. This can be EXPLAINED by comparing the STABILITY of the ANIONS of phenol and cresol after losing a proton

Anion of cresol is less stable due to electron donating (inductive) effect of `-CH_(3)`.
Discussion
6343.

Which one of the following is a tribasic acid?

Answer»

HYDROCHLORIC acid
nitric acid
SULPHURIC acid
phosphoric acid

SOLUTION :A tribasic acid hasthree repleaceable hydrogen atoms to donate to a base during an acid base REACTION phosphoric acid is a tribasic acid
Discussion
6344.

Transition metals lie in the periodic table between groups

Answer»

3 RD and 4th
2nd and 13th
1st and 2nd
2nd and 12th

Answer :B
Discussion
6345.

Answer any FOUR of the following questions. b. (i) Name the product formed for the reaction of isopropyl iodide on alcoholic KOH. (ii) What is the condition to be satisfied for a compound to be chiral?

Answer»

Solution :(a) `S_N1` means unimolecular nucleophilic substitution reaction.
In this reaction rate depends only on the concentration of ALKYL halide i.e.,`r prop [R-X]`
where `.r.` = rate of the reaction
`[R-X]` = Molar conc of alkyl halide
`S_N1` mechanism follows `1^(st)` order kinetics & the mechanism is of 2 STEPS.
Step 1 :
`underset("t - butyl bromide")(CH_3-underset(CH_3)underset(|)overset(CH_3)overset(|)(C )-Br) overset("Slow ionization")( Since this step is slow step, it is rate determined step.
Step 2 :
`CH_3-underset(CH_3)underset(|)overset(CH_3)overset(|)(C )o+ + OH^(o+)to underset("t - butyl bromide")(CH_3-underset(CH_3)underset(|)overset(CH_3)overset(|)(C )-OH)`
(b) (i) Propene
(ii) The molecule should contain asymmetric carbon atom (The C-atom is bonded to four different atoms or groups)
(c) Equimolar mixture of d- and l-isomers of an optically active compound.
Detailed Answer:
(c) When equal amounts of TWO enatiomers d and l are MIXED together , it gives an optically inactive form called as racemic mixture.
Discussion
6346.

Which of the following metals cannot be extracted by carbon reduction process ?

Answer»

LEAD
ALUMINIUM
MERCURY
Zinc

Answer :B
Discussion
6347.

Which of the following solution is more concentrated

Answer»

0.3% `H_3PO_4`
0.3 M `H_3PO_4`
0.3m `H_3PO_4`
0.3 N `H_3PO_4`

ANSWER :B
Discussion
6348.

Which of the following metals are obtained by auto reduction method?

Answer»


ANSWER :d
Discussion
6349.

which of the following molecules the central atom has sp^2-hybridisation ?

Answer»

`BeF_2 `
`BF_3 `
`C_2H_2 `
`NH_3 `

ANSWER :B
Discussion
6350.

White lung cancer' is caused by

Answer»

Asbestos
Silica
textiles
Paper

Answer :C
Discussion