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16551.

Select the incorrect pairA. B. C. `:CH_2rarr` NucleophileD. `dot(C)H_(3) rarr` Electron deficient species

Answer» Correct Answer - C
`:CH_(2)` is a Nucleophila
Discussion
16552.

Which reaction is not an example of nucleophilic addition reaction?A. `CH_(3)-CHOunderset((2)H_(2)O)overset((1)LiAID_(4))toH_(3)C-underset(H)underset(|)overset(OH)overset(|)(C)-D`B. `H_(3)C-CHOoverset(HCN)rarroverset(OH)overset(|)(H_(3)C-CH-CN`C. `H_(3)C-CHOunderset((2)H_(2)O)overset((1)CH_(3)MgBr)tooverset(OH)overset(|)(H_(3)C-CH-CH_(3)`D. `H_(3)C-COOCH_(3)underset(-CH_(3)O^(-))overset(NH_(2)^(-))to H_(3)C-CONH_(2)`

Answer» Correct Answer - D
Reaction `(D)` is an example of `S_(N)2`. The reaction.
Discussion
16553.

Consider a circular coil of wire carrying constant current I, forming a magnetic dipole. The magnetic flux through an infinite plane that contains the circular coil and excluding the circular coil area is given by ϕi. The magnetic flux through the area of the circular coil area is given by ϕ0. Which of the following option is correct ?

Answer»

Answer is (1) ϕi = – ϕ0
Discussion
16554.

Statement-1: In the circuit shown assume both cell are ideal and of fixed e.m.f., the resistor R1 is fixed, the resistor R2 is non zero variable. Then the electric power delivered to the resistor R1 is independent of value of resistanceStatement-2: If potential difference across a fixed resistance is unchanged, the power delivered to the resistor remains unchanged.(1) Statement -1 is True, Statement -2 is True ; Statement -2 is a correct explanation for Statement -1 (2) Statement-1 is true, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-1 (3) Statement-1 is true; Statement-2 is False(4) Statement-1 is False, Statement-2 is True

Answer»

Correct option  Statement -1 is True, Statement -2 is True ; Statement -2 is a correct explanation for Statement -1
Discussion
16555.

Statement-1 : A current flows in a conductor when there is electric field within the conductor.Statement-2 : The drift velocity of electrons in presence of electric field decreases.(1) Statement -1 is True, Statement -2 is True ; Statement -2 is a correct explanation for Statement -1(2) Statement-1 is true, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-1(3)  Statement-1 is true; Statement-2 is False(4)  Statement-1 is False, Statement-2 is True

Answer»

Correct option (4) Statement-1 is False, Statement-2 is True
Discussion
16556.

Statement-1: At Cryogenic temperatures, the electrical resistivity in metallic conductors diminishes.Statement-2: Thermal oscillations of atoms which hinder motion of free electrons under the influence of an external field become insignificant.(1) Statement -1 is True, Statement -2 is True ; Statement -2 is a correct explanation for Statement -1 (2)  Statement-1 is true, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-1 (3)  Statement-1 is true; Statement-2 is False(4)   Statement-1 is False, Statement-2 is true

Answer»

Correct option (1) Statement -1 is True, Statement -2 is True ; Statement -2 is a correct explanation for Statement -1 
Discussion
16557.

A smooth circular groove has a smooth vertical wall as shown in figure. A block of mass m moves against the wall with a speed v. Which of the following curve represents the correct relation between the normal reaction on the block by the wall (N) and speed of the block (v) ?

Answer»

Correct option is (A)

N = mv2 / r

Curve is parabola 

Y = kx2
Discussion
16558.

A small ball thrown at an initial velocity `v_(0)` at an angle `alpha` to the horizontal strikes elastically with a smooth vertical wall moving towards it at a horizontal velocity v and returns to the point from which it was thrown. Determine the time t from the beginning of motions to the moment of impact with vertical wall. Neglect friction losses.A. `t=(v_(0)sinalpha(v_(0)cosalpha+2v))/(g(v_(0)cosalpha+v))`B. `t=(v_(0)sinalpha(v_(0)cosalpha-2v))/(g(v_(0)cosalpha+v))`C. `t=(v_(0)sinalpha(v_(0)cosalpha+2v))/(g(v_(0)cosalpha-v))`D. `t=(v_(0)cosalpha(v_(0)sinalpha+2v))/(g(v_(0)sinalpha+v))`

Answer» Correct Answer - A
Since the wall is smooth, the impact against the wall does not alter the vertical component of the ball velocity. Therefore the total time `t_(1)` of motion of the ball is the total time of the ascent and descent of the body thrown upwards at a velocity `v_(0) sinalpha` in the gravitational field. Consequently `t_(1)=2v_(0)sin(alpha)/(g)`. The motion of the ball along the horizontal is the sum of two motions Before the collision with the wall it moves at a velocity `v_(0)cosalpha+v`. Since the impact is perfectly elastic, the ball moves away from the wall after the collision at a velocity `v_(0)cosalpha+v`. Therefore the ball has the following horizontal velocity relative tot he ground
`(v_(0)cosalpha+v)+v=v_(0)cosalpha+2v`.
If the time of motion before the impact is `t`. By equating the distance covered by the ball before ad after te collision, we obtain the following equation:
`v_(0)cosalpha alpha.t=(t_(1)-t)(v_(0)cosalpha+2v)`
since the total time of motion of the ball is `t_(1)=2v_(0)sin(alpha)/(g)`. we find the thhat
`t=(v_(0)sinalpha(v_(0)cosalpha+2v))/(g(v+(0)cosalpha+v))`
Discussion
16559.

A ________ system is one in which no variation of conditions is possible without one phase disappearing.(a) Variant(b) Invariant(c) Constant(d) None of the mentioned

Answer» Correct answer is (b) Invariant

Easiest explanation: A invariant system is one in which no variation of conditions is possible without one phase disappearing.
Discussion
16560.

How many brick lined tanks are used in tank slaking method?(a) 2(b) 1(c) 4(d) 3

Answer» Correct option is (a) 2

To elaborate: Two tanks are used for tank slaking method.  One is constructed 45cm deep, at a higher level.  Other one adjoining the first one is constructed 60-75cm deep, at lower level.
Discussion
16561.

Rate of hydration (slaking) does not depend on:(a) Degree of burning of lime(b) Degree of agitation(c) Atmospheric conditions(d) Composition of lime

Answer» Correct answer is (c) Atmospheric conditions

Easiest explanation: Over and under burned lime is undesirable.  Composition of lime (pure, clay) are important to determine slaking.  Pure lime slakes vigorously.  Slaking is carried in tank in closed conditions.  Too little agitation results in uneven mixing and leads to drowning or unhydrated particles of CaO.
Discussion
16562.

If excess of HI is added to methanol, it formsA. chloroformB. methyl iodideC. both of theseD. none of these

Answer» Correct Answer - B
Discussion
16563.

Slaking of lime refers to:(a) Mixing NaCl in hydraulic lime(b) Mixing water in quick lime(c) Mixing water in limestone(d) Mixing NaCl in quick lime

Answer» Right answer is (b) Mixing water in quick lime

Best explanation: Slaking refers to the process of mixing water in quick lime.  Only after this, it can be used in construction works.
Discussion
16564.

Covalent bond is formed by the overlaping of atomic orbitals. 1. What is meant by orbital overlapping? 2. What are the 3 types of overlapping?

Answer»

1. Orbital overlapping is the partial interpenetration or merging of atomic orbitals. It results in the pairing of electrons. Greater the overlap the stronger is the bond formed between two atoms.

2. s-s overlapping 

s-p overlapping 

p-p overlapping
Discussion
16565.

Reaction of HI with ether followsA. SN1 pathwayB. SN2 pathwayC. both of theseD. none of these

Answer» Correct Answer - B
Discussion
16566.

Butan -2 ol is also called asA. tert butyl alcoholB. sec butyl alcoholC. isobutyl alcoholD. n-butyl alcohol

Answer» Correct Answer - B
Discussion
16567.

SECONDARY SUFFIX FOR carboxylix acid ISA. olB. oic acidC. oneD. none of these

Answer» Correct Answer - A
Discussion
16568.

Common name for HCOOH isA. formic acidB. methanoic acidC. none of theseD. both of these

Answer» Correct Answer - A
Discussion
16569.

Common name for HCOOH isA. FORMIC ACIDB. ACETIC ACIDC. ETHANOIC ACIDD. METHANOIC ACID

Answer» Correct Answer - A
Discussion
16570.

Which of the following naming of compound is correct representation?A. propane-1,2,3-trioic acidB. propane-1,2,3-tricarboxylic acidC. both of theseD. none of these

Answer» Correct Answer - B
Discussion
16571.

Metals reacts with mineral acids to evolve ________ gas.A. hydrogenB. chlorineC. sulphurD. none of these

Answer» Correct Answer - A
Discussion
16572.

HCOCl isA. ethanoyl chlorideB. methanoyl bromideC. chloromethanoneD. none OF THESE

Answer» Correct Answer - B
Discussion
16573.

Which metal reacts with very dil `HNO_3`?A. MnB. AlC. ZnD. none of these

Answer» Correct Answer - A
Discussion
16574.

What weight of hydrogen at `STP` could be contained in a vessel that holds `4.8 g` oxygen at `STP`?A. 4.8 gB. 3.0 gC. 0.6 gD. 0.3 g

Answer» Correct Answer - D
`4.8 g O_2 = (408)/(32) mol O_2 = (4.8)/(32) xx 2g H_2 = 0.3 g`.
Discussion
16575.

`1 mol` of `NH_(3)` gas at `27^(@)C` is expanded under adiabatic condition to make volume `8` times `(gamma=1.33)`. Final temperature and work done, respectively, areA. `150 K, 900 cal`B. `150 K, 400 cal`C. `250 K, 1000 cal`D. `200 K, 800 cal`

Answer» Correct Answer - A
`T_2 = T_1 ((V_1)/(V_2))^(gamma -1) = 150 K`
`w = -C_V Delta T = - C_V(T_2 -T_1)`
=`-3 xx 2 xx (150 - 300) = 900 cal`.
Discussion
16576.

Calculate the weight of bacl2

Answer»

Answer: 208.23 g/mol

ANSWER:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::208.23g/mol
Discussion
16577.

qusi static process

Answer»

A quasi static process is a process carried out very very slowly, in an attempt to reach as close as possible to a reversible process.Quasistatic process are not always reversible.
Discussion
16578.

`K_(p)` for the reaction `MgCO_(3_((s))) to MgO_((s)) + CO _(2_((g))) " is " 9 xx 10^(-10)`. Calculate `Delta G^(@)` for the reaction at `25^(@)C`.

Answer» Correct Answer - `Delta G^(@) = 51.653 kJ mol^(-1)`
Given : `K_(p) = 9 xx 10^(-10)`
Temperature `= T = 273 + 25 =298 K `
`Delta G^(@) = ? `
`Delta G^(@) =- 2 .303 RT log_(10) K_(p)`
`=-2.303 x 8.314 xx 298 xx log_(10) 9 xx 10^(-10)`
`=- 2.303 xx 8. 314 xx 298 xx [bar(10).9542]`
`=- 2.303 xx 8.314 xx 298 xx [ - 9.0458]`
`= 51683 J mol^(-1)`
`=51. 683 kJ mol^(-1)`
Discussion
16579.

Determine whether the following reaction will be spontaneous or non- spontaneous under standard conditions. `Zn_((s)) +Cu^(2+) to Zn^(2+) + Cu_((s)) " "DeltaH^(@) =- 219 kJ, DeltaS^(@) =- 21 JK^(-1)`

Answer» Correct Answer - The reaction is spontaneous.
Given : `DeltaH^(@) =- 219 kJ`
`Delta S^(@) =-21 JK^(-1) = 0.021 kJK^(-1)`
`Delta G^(@)= ?`
for standard conditions : Pressure = 1 atm
Temperature = T = 298 K
`Delta G^(@) = Delta H^(@) = T Delta S^(@)`
`=- 219 - 298 xx (-0.021)`
`=- 219 + 6.258`
`=- 212 .742 kJ`
Since `Delta G lt 0` the reaction is spontaneous.
Discussion
16580.

What would be the reduction potential of an electrode at 298 K , which originally contained ` 1K_(2)Cr_(2)O_(7)` solution in acidic buffer solution of `pH = 1.0` and which was treated with 50% of the Sn necessary to reduce all `Cr_(2)O_(7)^(2-)" to "Cr^(3+)`.Assume pH of solution remains constant. Given : `E^(0)._(Cr_(2)O_(7)^(2-)//Cr^(3+), H^(+))= 1. 33 V , log 2 = 0.3 , (2.303RT)/F = 0.06`A. `1.285 V`B. `1.193 V`C. `1.187 V`D. None of these

Answer» Correct Answer - C
Discussion
16581.

(i) Write the composition of bleaching powder.(ii) What happens when NaCl is heated with conc. H2SO4 in the presence of MnO2. Write the chemical equation.

Answer»

[Hint :  (i) Ca(OCl)2.CaCl2.Ca(OH)2.2H2O]
Discussion
16582.

The solubility of A2X3 is y mol dm–3. Its solubility product is(a) 6y4 (b) 64y4(c) 36y5 (d) 108y5

Answer»

Correct option: (d) 108 y5

Explanation: 

A2B3 ⇌ 2A+3 + 3B–

                2S      3S

Ksp = [A+3]2 [B–2]3 = (2S)2 (3S)3

Ksp = 108 y5
Discussion
16583.

What are buffer solutions? Given an example for an acidic buffer.

Answer»

The solution which resist the pH or pOH when an acid or base is added to it. Buffer solution is a mixture of weak electrolyte and its salt. A solution containing a weak acid and its salt with a strong base. 

(i) CH3COOH + CH3COONa 

(ii) HCOOH + HCOOK
Discussion
16584.

A colourless pungent smelling gas, which easily liquefies to a colourless liquid and freezes to a white crystalline solid, gives dense white fumeswith ammonia. Identify the gas and write the chemical equation for its laboratory preparation.

Answer»

[Hint : NaCl + H2SO4 (conc.)->  NaHSO4 + HCl]
Discussion
16585.

Calculate the solubility of A2X3 pure water, Assuming that neither king of ion reacts with water. The solubility product of A2X3 Ksp = 1.1 × 10-23. Explain with equation.

Answer»

ksp = [A3+]2 [X-2]3 = [2s]2 [3s]3 =108 s5 

S5 = 1.1 x 10-23/108 = 1 × 10-25 

S5 = 1 × 10-5 mol dm-3
Discussion
16586.

pH of .01 M KOH solution will be ........

Answer»

pH of .01 M KOH solution will be 12.
Discussion
16587.

Conjugate base of a strong acid is a .....

Answer»

Conjugate base of a strong acid is a Weak base.
Discussion
16588.

Water is a conjugate base of ......

Answer»

Water is a conjugate base of H3O+.
Discussion
16589.

The species acting both as bronsted acid and base is ......(a) PO3-4(b) HSO4-(c) O2-(d) H2PO-2

Answer»

The species acting both as bronsted acid and base is HSO4-
Discussion
16590.

Congugate base of a strong acid is a .......(a) Strong base (b) Strong acid (c) Weak acid (d) Weak base(e) Salt

Answer»

Congugate base of a strong acid is a Weak base.
Discussion
16591.

(i) Explain why BF3 molecule has zero dipole moment although the B-F bonds are polar?(ii) Alkali metals and Halogens form Ionic compounds. Give reason.

Answer»

(i) Shape of BF3 is Trigonal planar.

The net sum of bond moment is equal to zero because of cancellation of bond moments due to symmetry in the molecule.

(ii) Alkali metals have low ionization enthalpy hence they easily form cations.

Halogens have high electron gain enthalpy hence they easily form Anions.
Discussion
16592.

Would you expect the first ionisation enthalpies for two isotopes of the same element to be the same or different? Justify your answer.

Answer» Two isotopes of the same element have same number of electrons, same nuclear charge, same size and hence they are expected to have same ionisaton enthalpy.
Discussion
16593.

In the equilibrium reaction CaCO3(s) → CaO(s) + CO2(g) the equilibrium constant is given by .......

Answer»

The equilibrium constant is given by PCO2.
Discussion
16594.

Explain mechanism of chlorination of methane.

Answer»

The mechanism involves three steps:

(1) Initiation: A chlorine molecule absorbs energy from sunlight to form free radicals.

(2) Propagation: A chlorine free radical reacts with methane forming a HCl and methyl free radical.

CH4 + Cl• → CH3• + HCl

(b) The methyl free radical attack chlorine molecule forming a methyl chloride and chlorine free radical

CH3• + Cl2 → CH3Cl + Cl

Termination: The two free radical combines to form product.

Cl• + Cl• → Cl (Chlorine)

CH3• + CH3•→ C2H6 (Ethane)

CH3• + Cl• → CH3Cl (Methyl Chloride)
Discussion
16595.

Write reaction of justify amphoteric nature of aluminium.

Answer» Aluminium dissolves in both acids and alkalis and is amphoteric in nature.
`2Al_((s))+3H_(2)SO_(4(aq))toAl_(2)(SO_(4))+3H_(2)`
`2Al_((s))+2NaOH_((aq))+6H_(2)O_((l))tounderset("Sodium tetrahydroxoaluminate(III)")(2Na^(o+)[Al(OH)_(4)]_((aq))^()+3H_(2)uarr(g))`
Discussion
16596.

(a) Why is separation of lanthanoid elements dificult ?(b) Transition metal exhibit higher enthalpies of atomization. Explain why ?(c) Why have the transition metal high enthalpy of hydration ?

Answer»

(a) Due to lanthanide contraction, the size of           these elements is nearly same.
(b) Transition metal contain large number of unpaired electrons, and they
have strong interatomic attractions.
(c) Due to their small size and large nuclear charge.
Discussion
16597.

Explain the Amphoteric nature of Aluminium, give equations.

Answer»

Aluminium reacts both with acid and base so it behaves as amphoteric nature.

2Al(s) + 6HCl(aq) → 2Al3+(aq) + 6Cl–(aq) + 3H2(g) behaving as acid.

2Al(s) + 2NaOH(aq) + 6H2O(l) → 2Na+[Al(OH)4]– (aq) + 3H2(g) behaving as base.
Discussion
16598.

Explain the mechanism of chlorination of Methane, with equations.

Answer»

Mechanism of chlorination of methane involves three types.

Step 1: Initiation : Chlorine absorbs energy and undergoes homolysis to give chlorine free radicals.

Cl - Cl + hy → 2Cl+ 

Step 2: Propagation : Chlorine free radical reacts with methane to give methyl free radical.

Cl• + CH4 → CH3• + HCl

The methyl free radical reacts with chlorine to form methyl chloride and chlorine free radical.

CH3• + Cl2 → CH3Cl + Cl•

Step 3: Termination: Free radicals combine to form stable products.

Cl• + Cl• → Cl2 (Chlorine)

CH3• + Cl• → C2H6 (Ethane)

CH3• + Cl• → CH3Cl (Methyl Chloride)
Discussion
16599.

Name the type of hybridization of(i) Boron in Diborane(ii) Carbon in Graphite

Answer»

(i) sp3 hybridization

(ii) sp2 hybridisation
Discussion
16600.

Which of the following observations made from the Ellingham diagram is wrong ?A. The slope of the curves of the formation of metal oxides is negativeB. Each curve is straight line except when some change takes place in phase `(S - 1 or 1 rarr g)`C. In the case of less reactive (or less electroposities metal like `Ag and Hg, Delta G^(Ө)` become positive at relatively low temperatures .D. Any matel oxide with lower value of `Delta G^(Ө)` is more stable than a metal oxide with higher `Delta G^(Ө)` .

Answer» Correct Answer - a
Consider the formation of a metel oxide `(M_(2)O)`
`2sM(s) + O_(2)(g) rarr 2M_(2)O(s)`
Is this reaction there is decreases in the value of `Delta S` ior `M_(2)O` solid and `O_(2)` is a gas i.e. `Delta S` is negative .This if temperature is increases `T Delta S` becomes . becomes more negative as is the equation
`Delta G = Delta H - T Delta S Delta H ` is tengative formation of metal oxide is enothermic and `T Delta S` (it negative quantity ) is substrcted `Delta G` becomes less negative i.e. `Delta G` is likely to increases with rise it in temperature and ythis trend is confirmed from the corves of metal oxide its Ellingham diagram .The slope of the curve of th e formation of metal oxides is `- ve` because `Delta G` becomes less negative or temperature with the rise in temperature
The temperature at which such a change occure is indicated by an incrfeases in the slope on the `- ve` side for example , in the `Zn- ZnO` "`curve , "the melting of Zn is incates by the first abropt increases in the" `-ve` "slope at temperature" `692K`. "The indicates that both silver oxide (Ag,O) and merccury oxide (HgO) are unstate and decompose at relatively low temperature"
`2Ag_(2)O overset (Delta) To 4Ag + O_(2)`
`2HgO overset (Delta) To 2Hg + o_(2)`
This amples that the metal oxide placed higher to the diagram can be reducted by the metal invcolved in the formation of the oxide placed lower in the diagram. For example by `Ct`,
` Ct_(2) O_(3) + Al rarr Al_(2)O_(3) + 2Ct` ltvbrgt Thus the relactive tendency of the various metalsto act in reducing agents is
`Cu gt Mg gt Al gt Cr gt Zn gt Fe gt Ni`
Discussion