46295 + Interview Questions in Chemistry

1.	From B2H6, all the following can be prepared except?
Answer» From $B_{2} H_{6}$ , all the following can be prepared except?

Discussion

2.	In which of te following options order of arrangement does not agree with the variation of property indicated against it? (a)Al3+<Mg2+<Na+<F− (Increasing ionic size) (b) B < C < N < O (Increasing first ionlsation enthalpy) (c) I < Br < Cl< F (increasing electron gain enthalpy) (d) Li < Na< K < Rb (Increasing metallic radius)
Answer» In which of te following options order of arrangement does not agree with the variation of property indicated against it? (a) $A l^{3 +} < M g^{2 +} < N a^{+} < F -$ (Increasing ionic size) (b) B < C < N < O (Increasing first ionlsation enthalpy) (c) I < Br < Cl< F (increasing electron gain enthalpy) (d) Li < Na< K < Rb (Increasing metallic radius)

Discussion

3.	Does E2 reaction proceeds with 3°>2°>1° or 1°>2°>3° of alkyl halide.And what's the reason for it?
Answer» Does E2 reaction proceeds with 3°>2°>1° or 1°>2°>3° of alkyl halide.And what's the reason for it?

3.

Does E2 reaction proceeds with 3°>2°>1° or 1°>2°>3° of alkyl halide.And what's the reason for it?

Answer»

Does E2 reaction proceeds with

3°>2°>1° or

1°>2°>3° of alkyl halide.And what's the reason for it?

Discussion

4.	Why does hydrogen occur in a diatomic form rather than in a monoatomic form under normal conditions?
Answer» Why does hydrogen occur in a diatomic form rather than in a monoatomic form under normal conditions?

Discussion

5.	The relationship between the dissociation energy of N2 and is :N2+
Answer» The relationship between the dissociation energy of $N_{2}$ and is : ${N_{2}}^{+}$

Discussion

6.	Rhombic sulphur is melted in a dish. It is then cooled till a crust is formed. Two holes are made to pour out remaining liquid on removing crust. Crystals of which of the following is/are obtained above 95.5∘ ?
Answer» Rhombic sulphur is melted in a dish. It is then cooled till a crust is formed. Two holes are made to pour out remaining liquid on removing crust. Crystals of which of the following is/are obtained above ${95.5}^{\circ}$ ?

Discussion

7.	For the non - stoichiometric relation : 2A+B→C+D, the following kinetic data was obtained in the seperate experiments, all at 298 K. Initial concentrationInitial concentrationInitial rate offormation[A][B](mol L−1 s−1)0.1 M0.1 M1.2×10−30.1 M0.2 M1.2×10−30.2 M0.1 M2.4×10−3 The rate law for the formation of C is:
Answer» For the non - stoichiometric relation : $2 A + B \to C + D$ , the following kinetic data was obtained in the seperate experiments, all at 298 K. $\begin{matrix} Initial concentration & Initial concentration & Initial rate of formation [A] & [B] & {(mol L}^{- 1} s^{- 1}) 0.1 M & 0.1 M & 1.2 \times 10^{- 3} 0.1 M & 0.2 M & 1.2 \times 10^{- 3} 0.2 M & 0.1 M & 2.4 \times 10^{- 3} \end{matrix}$ The rate law for the formation of $C$ is:

Discussion

8.	Consequences of metal excess defect?
Answer» Consequences of metal excess defect?

Discussion

9.	How is C3 plants benefited by global warming?
Answer» How is C3 plants benefited by global warming?

Discussion

10.	Work done in reversible expansion is...... (1) Minimum (2) Maximum (3) zero (4) not predictable
Answer» Work done in reversible expansion is...... (1) Minimum (2) Maximum (3) zero (4) not predictable

Discussion

11.	Which of the following does not apply to metallic bond ? 1) Overlapping valence electrons 2) Mobile valence electrons 3) Delocalized electrons 4) Highly directed bonds
Answer» Which of the following does not apply to metallic bond ? 1) Overlapping valence electrons 2) Mobile valence electrons 3) Delocalized electrons 4) Highly directed bonds

11.

Which of the following does not apply to metallic bond ? 1) Overlapping valence electrons 2) Mobile valence electrons 3) Delocalized electrons 4) Highly directed bonds

Answer»

Which of the following does not apply to metallic bond ?

1) Overlapping valence electrons

2) Mobile valence electrons

3) Delocalized electrons

4) Highly directed bonds

Discussion

12.	If we have to find the energy of an orbit and it isinot given that its a Bohr's atom or orbit so then what wr have to do to find the energy of an orbit
Answer» If we have to find the energy of an orbit and it isinot given that its a Bohr's atom or orbit so then what wr have to do to find the energy of an orbit

Discussion

13.	When ethyl alcohol is heated with red phosphorus and $HI$, then which of the following is formed
Answer» When ethyl alcohol is heated with red phosphorus and $HI$, then which of the following is formed

Discussion

14.	Which of the following is not a non-biodegradable pollutant?
Answer» Which of the following is not a non-biodegradable pollutant?

Discussion

15.	The ions of NaF and MgO all have the same number of electrons and the internuclear distance are about the same (235pm and 215pm).Why then are the melting points of NaF and MgO so different (992 degree C and 2642degree celcius)?
Answer» The ions of NaF and MgO all have the same number of electrons and the internuclear distance are about the same (235pm and 215pm).Why then are the melting points of NaF and MgO so different (992 degree C and 2642degree celcius)?

Discussion

16.	Glyptal polymer is obtained from the reaction between ethylene glycol and:
Answer» Glyptal polymer is obtained from the reaction between ethylene glycol and:

Discussion

17.	Identify the correct order of reactivity in electrophilic substitution reactions of the following compounds Benzene, methyl benzene, Chlorobenzene, nitro benzene:
Answer» Identify the correct order of reactivity in electrophilic substitution reactions of the following compounds Benzene, methyl benzene, Chlorobenzene, nitro benzene:

Discussion

18.	In Friedel crafts alkylation and acylation the attacking reagent is an:
Answer» In Friedel crafts alkylation and acylation the attacking reagent is an:

Discussion

19.	The diffrence between heat of reaction at constant volume and constant pressure for the reaction C2H2(g)+52O2(g)→2CO2(g)+H2O(l). At 300K in kcal is : [Given: R=2 cal/mol.K]
Answer» The diffrence between heat of reaction at constant volume and constant pressure for the reaction $C_{2} H_{2} (g) + \frac{5}{2} O_{2} (g) \to 2 C O_{2} (g) + H_{2} O (l) . A t 300 K i n k c a l i s : [G i v e n : R = 2 c a l / m o l . K]$

19.

The diffrence between heat of reaction at constant volume and constant pressure for the reaction C2H2(g)+52O2(g)→2CO2(g)+H2O(l). At 300K in kcal is : [Given: R=2 cal/mol.K]

Answer»

The diffrence between heat of reaction at constant volume and constant pressure for the reaction

$C_{2} H_{2} (g) + \frac{5}{2} O_{2} (g) \to 2 C O_{2} (g) + H_{2} O (l) . A t 300 K i n k c a l i s : [G i v e n : R = 2 c a l / m o l . K]$

Discussion

20.	KO2 (potassium superoxide) is used in oxygen cylinders in space and submarines because it:
Answer» $K O_{2}$ (potassium superoxide) is used in oxygen cylinders in space and submarines because it:

Discussion

21.	Which of the following will have same value of van't Hoff factor as that of K4[(Fe(CN)6]?
Answer» Which of the following will have same value of van't Hoff factor as that of K₄[(Fe(CN)₆]?

Discussion

22.	For a given concentration, the ionic conductance in water is of the order:
Answer» For a given concentration, the ionic conductance in water is of the order:

Discussion

23.	For an aqueous solution freezing point is – 0.186∘C. Elevation of the boiling point of the same solution is (Kf =1.86 mole−1 kg and Kb = 0.512 mole−1 kg)
Answer» For an aqueous solution freezing point is – ${0.186}^{\circ} C$ . Elevation of the boiling point of the same solution is ( $K_{f}$ =1.86 $m o l e^{- 1}$ kg and $K_{b}$ = 0.512 $m o l e^{- 1}$ kg)

Discussion

24.	The conductance of a 0.0015 M aqueous solution of a weak monobasic acid was determined by using a conductivity cell consisting of Pt electrodes. The distance between the electrodes is 120 cm with an area of cross section of 1 cm2 . The conductance of this solution was found to be 5×10−7S. The pH of the solution is 4. The value of limiting molar conductivity (∧0m) of this weak monobasic acid in aqueous solution is Z×102 S cm−1mol−1 . The value of Z is?
Answer» The conductance of a $0.0015 M$ aqueous solution of a weak monobasic acid was determined by using a conductivity cell consisting of $P t$ electrodes. The distance between the electrodes is $120 cm$ with an area of cross section of $1 {cm}^{2}$ . The conductance of this solution was found to be $5 \times 10^{- 7} S$ . The $p H$ of the solution is $4$ . The value of limiting molar conductivity $(\land_{m}^{0})$ of this weak monobasic acid in aqueous solution is $Z \times 10^{2} {S cm}^{- 1} {mol}^{- 1}$ . The value of $Z$ is?

Discussion

25.	The compounds [Co(SO4)(NH3)5]Br and [Co(SO4)(NH3)5]Cl represent (a) linkage isomerism (b) ionisation isomerism (c) coordination isomerism (d) no isomarism
Answer» The compounds $[C o (S O_{4}) (N H_{3})_{5}] B r$ and $[C o (S O_{4}) (N H_{3})_{5}] C l$ represent (a) linkage isomerism (b) ionisation isomerism (c) coordination isomerism (d) no isomarism

Discussion

26.	Calculate the value of azimuthal quantum number for the subshell notation 4d?
Answer» Calculate the value of azimuthal quantum number for the subshell notation 4d?

Discussion

27.	At a given temperature, amongest Oxygen and Hydrogen, the r.m.s. velocity will be greater for
Answer» At a given temperature, amongest Oxygen and Hydrogen, the r.m.s. velocity will be greater for

Discussion

28.	Ferric oxide crystallises in a hexagonal close-packed array of oxide ions with two out of every three octahedral holes occupied by ferric ions. Derive the formula of the ferric oxide .
Answer» Ferric oxide crystallises in a hexagonal close-packed array of oxide ions with two out of every three octahedral holes occupied by ferric ions. Derive the formula of the ferric oxide .

Discussion

29.	Among the complex ions, [Co(NH2−CH2−CH2−NH2)2Cl2]+, [CrCl2(C2O4)2]3−, [Fe(H2O)4(OH)2]+, [Fe(NH3)2(CN)4]−, [Co(NH2−CH2−CH2−NH2)2(NH3)Cl]2+ and [Co(NH3)4(H2O)Cl]2+, the number of complex ion(s) that show(s) cis-trans isomerism is:
Answer» Among the complex ions, $[C o (N H_{2} - C H_{2} - C H_{2} - N H_{2})_{2} C l_{2}]^{+}, [C r C l_{2} (C_{2} O_{4})_{2}]^{3 -}, [F e (H_{2} O)_{4} (O H)_{2}]^{+}, [F e (N H_{3})_{2} (C N)_{4}]^{-}, [C o (N H_{2} - C H_{2} - C H_{2} - N H_{2})_{2} (N H_{3}) C l]^{2 +}$ and $[C o (N H_{3})_{4} (H_{2} O) C l]^{2 +}$ , the number of complex ion(s) that show(s) cis-trans isomerism is:

Discussion

30.	The total pressure of a mixture of 8g of oxygen and 14g of nitrogen contained in a 11.2L vessel at 0o C is
Answer» The total pressure of a mixture of 8g of oxygen and 14g of nitrogen contained in a 11.2L vessel at $0^{o} C$ is

Discussion

31.	An unknown compound ( A) has a molecular formula C4 H6. When (A) is treated with excess of Br2 a new substance (B) with formula C4H6 Br4 is formed. (A) forms a white ppt. with ammoniacal silver nitrate. Compound A is
Answer» An unknown compound ( A) has a molecular formula C₄ H₆.When (A) is treated with excess of Br₂ a new substance (B) with formula C₄H₆ Br₄ is formed. (A) forms a white ppt. with ammoniacal silver nitrate. Compound A is

31.

An unknown compound ( A) has a molecular formula C4 H6. When (A) is treated with excess of Br2 a new substance (B) with formula C4H6 Br4 is formed. (A) forms a white ppt. with ammoniacal silver nitrate. Compound A is

Answer»

An unknown compound ( A) has a molecular formula C₄ H₆.When (A) is treated with excess of Br₂ a new substance (B) with formula C₄H₆ Br₄ is formed. (A) forms a white ppt. with ammoniacal silver nitrate. Compound A is

Discussion

32.	Slowest step of the multistep reaction is known as
Answer» Slowest step of the multistep reaction is known as

Discussion

33.	In the following reactions: Me−CH=CH−MeBr2−−−→CCl4A2NaNH2−−−−−→BNa/liq.NH3−−−−−−−→C The product(c) is:
Answer» In the following reactions: $M e - C H = C H - M e B r_{2} - -- \to C C l_{4} A 2 N a N H_{2} - ---- \to B N a / l i q . N H_{3} - ------ \to C$ The product(c) is:

Discussion

34.	Assume that a box full of electrons had a total charge of −96368 C. The number of moles of eletcrons present inside the box is Given:e=−1.6×10−19 C
Answer» Assume that a box full of electrons had a total charge of $- 96368 C$ . The number of moles of eletcrons present inside the box is $Given : e = - 1.6 \times 10^{- 19} C$

Discussion

35.	Which of the following occurs in dark reaction of photosynthesis?
Answer» Which of the following occurs in dark reaction of photosynthesis?

Discussion

36.	Two metallic oxides contain 27.6% and 30.0% oxygen respectively. If the formula of the first oxide is M3O4, then that of the second will be
Answer» Two metallic oxides contain 27.6% and 30.0% oxygen respectively. If the formula of the first oxide is M₃O₄, then that of the second will be

Discussion

37.	CH3CH2ClNaCN−−−−→XNi/H2−−−−→YAcetic Anhydride−−−−−−−−−−→Z 'Z' in the above reaction sequence is
Answer» $C H_{3} C H_{2} C l N a C N - --- \to X N i / H_{2} - --- \to Y Acetic Anhydride - --------- \to Z$ 'Z' in the above reaction sequence is

Discussion

38.	Give a chemical test to distinguish between the following pair of compounds 1: n-propyl alcohol and isopropyl alcohol 2: methanol and ethanol 3: cyclohexanol and phenol 4: propan-2-ol and 2 methylpropan-2-ol 5: phenol and anisole 6: ethanol and diethyl Ether
Answer» Give a chemical test to distinguish between the following pair of compounds 1: n-propyl alcohol and isopropyl alcohol 2: methanol and ethanol 3: cyclohexanol and phenol 4: propan-2-ol and 2 methylpropan-2-ol 5: phenol and anisole 6: ethanol and diethyl Ether

38.

Give a chemical test to distinguish between the following pair of compounds 1: n-propyl alcohol and isopropyl alcohol 2: methanol and ethanol 3: cyclohexanol and phenol 4: propan-2-ol and 2 methylpropan-2-ol 5: phenol and anisole 6: ethanol and diethyl Ether

Answer»

Give a chemical test to distinguish between the following pair of compounds

1: n-propyl alcohol and isopropyl alcohol

2: methanol and ethanol

3: cyclohexanol and phenol

4: propan-2-ol and 2 methylpropan-2-ol

5: phenol and anisole

6: ethanol and diethyl Ether

Discussion

39.	What is point mass and unit mass?
Answer» What is point mass and unit mass?

Discussion

40.	If 0.5 moles of BaCl2 is mixed with 0.2 moles ofNa3PO4 the maximum number of moles ofBa3(PO4)2 that can be formed
Answer» If 0.5 moles of BaCl2 is mixed with 0.2 moles ofNa3PO4 the maximum number of moles ofBa3(PO4)2 that can be formed

Discussion

41.	Cis-dicholoroethylene can be converted to trans-dichloroethylene by irradiation. During the interconversion (A) both the π and σ bonds are broken and reformed. (B) only the π bond is broken and reformed. (C) the C-Cl and C-H bonds are broken, H and Cl atoms interchange their positions and new bonds are formed. (D) both the π and σ bonds rotate along with the groups.
Answer» Cis-dicholoroethylene can be converted to trans-dichloroethylene by irradiation. During the interconversion (A) both the π and σ bonds are broken and reformed. (B) only the π bond is broken and reformed. (C) the C-Cl and C-H bonds are broken, H and Cl atoms interchange their positions and new bonds are formed. (D) both the π and σ bonds rotate along with the groups.

Discussion

42.	Cloud is a homogeneous or a heterogenous mixture
Answer» Cloud is a homogeneous or a heterogenous mixture

Discussion

43.	Select the WRONG pair regarding the relative contribution of various green-house gases.
Answer» Select the WRONG pair regarding the relative contribution of various green-house gases.

Discussion

44.	Which of the given statement(s) about N, O, P and Q with respect to M is (are) correct?
Answer» Which of the given statement(s) about N, O, P and Q with respect to M is (are) correct?

44.

Which of the given statement(s) about N, O, P and Q with respect to M is (are) correct?

Answer»

Which of the given statement(s) about N, O, P and Q with respect to M is (are) correct?

Discussion

45.	Choose the products formed by action of Na2CO3 on H3BO3
Answer» Choose the products formed by action of $N a_{2} C O_{3} on H_{3} B O_{3}$

Discussion

46.	In a semiconductor diode, p- side is earthed and to n-side is applied a potential of -2V: the diode shall
Answer» In a semiconductor diode, p- side is earthed and to n-side is applied a potential of -2V: the diode shall

Discussion

47.	What is the decreasing order of strength of the bases OH−,NH−2,HC≡C⊝ and CH3−CH⊝2
Answer» What is the decreasing order of strength of the bases $O H^{-}, N H_{2}^{-}, H C \equiv C^{⊝}$ and $C H_{3} - C H_{2}^{⊝}$

Discussion

48.	Phosphoric acid (H3PO4) is prepared in a two-step process: (1) P4+5O2→P4O10 (2) P4O10+6H2O→4H3PO4 In step (1), 62 g of phosphorus is made to react with excess oxygen to form P4O10 with 85 % yield. In step (2), the yield of H3PO4 obtained is 90 %. Calculate the mass of H3PO4 produced.
Answer» Phosphoric acid $(H_{3} P O_{4})$ is prepared in a two-step process: (1) $P_{4} + 5 O_{2} \to P_{4} O_{10}$ (2) $P_{4} O_{10} + 6 H_{2} O \to 4 H_{3} P O_{4}$ In step (1), $62 g$ of phosphorus is made to react with excess oxygen to form $P_{4} O_{10}$ with 85 % yield. In step (2), the yield of $H_{3} P O_{4}$ obtained is 90 %. Calculate the mass of $H_{3} P O_{4}$ produced.

Discussion

49.	The correct order of increasing basicity of the given conjugated bases is:
Answer» The correct order of increasing basicity of the given conjugated bases is:

Discussion

50.	If temperature of a black body increases from 7o C to 287o C then the rate of energy radiation increases by
Answer» If temperature of a black body increases from $7^{o} C t o 287^{o} C$ then the rate of energy radiation increases by

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

From B2H6, all the following can be prepared except?

Does E2 reaction proceeds with 3°&gt;2°&gt;1° or 1°&gt;2°&gt;3° of alkyl halide.And what's the reason for it?

Why does hydrogen occur in a diatomic form rather than in a monoatomic form under normal conditions?

The relationship between the dissociation energy of N2 and is :N2+

Rhombic sulphur is melted in a dish. It is then cooled till a crust is formed. Two holes are made to pour out remaining liquid on removing crust. Crystals of which of the following is/are obtained above 95.5∘ ?

Consequences of metal excess defect?

How is C3 plants benefited by global warming?

Work done in reversible expansion is...... (1) Minimum (2) Maximum (3) zero (4) not predictable

Which of the following does not apply to metallic bond ? 1) Overlapping valence electrons 2) Mobile valence electrons 3) Delocalized electrons 4) Highly directed bonds

If we have to find the energy of an orbit and it isinot given that its a Bohr's atom or orbit so then what wr have to do to find the energy of an orbit

When ethyl alcohol is heated with red phosphorus and \(HI\), then which of the following is formed

Which of the following is not a non-biodegradable pollutant?

The ions of NaF and MgO all have the same number of electrons and the internuclear distance are about the same (235pm and 215pm).Why then are the melting points of NaF and MgO so different (992 degree C and 2642degree celcius)?

Glyptal polymer is obtained from the reaction between ethylene glycol and:

Identify the correct order of reactivity in electrophilic substitution reactions of the following compounds Benzene, methyl benzene, Chlorobenzene, nitro benzene:

In Friedel crafts alkylation and acylation the attacking reagent is an:

The diffrence between heat of reaction at constant volume and constant pressure for the reaction C2H2(g)+52O2(g)→2CO2(g)+H2O(l). At 300K in kcal is : [Given: R=2 cal/mol.K]

KO2 (potassium superoxide) is used in oxygen cylinders in space and submarines because it:

Which of the following will have same value of van't Hoff factor as that of K4[(Fe(CN)6]?

For a given concentration, the ionic conductance in water is of the order:

For an aqueous solution freezing point is – 0.186∘C. Elevation of the boiling point of the same solution is (Kf =1.86 mole−1 kg and Kb = 0.512 mole−1 kg)

The compounds [Co(SO4)(NH3)5]Br and [Co(SO4)(NH3)5]Cl represent (a) linkage isomerism (b) ionisation isomerism (c) coordination isomerism (d) no isomarism

Calculate the value of azimuthal quantum number for the subshell notation 4d?

At a given temperature, amongest Oxygen and Hydrogen, the r.m.s. velocity will be greater for

Ferric oxide crystallises in a hexagonal close-packed array of oxide ions with two out of every three octahedral holes occupied by ferric ions. Derive the formula of the ferric oxide .

Among the complex ions, [Co(NH2−CH2−CH2−NH2)2Cl2]+, [CrCl2(C2O4)2]3−, [Fe(H2O)4(OH)2]+, [Fe(NH3)2(CN)4]−, [Co(NH2−CH2−CH2−NH2)2(NH3)Cl]2+ and [Co(NH3)4(H2O)Cl]2+, the number of complex ion(s) that show(s) cis-trans isomerism is:

The total pressure of a mixture of 8g of oxygen and 14g of nitrogen contained in a 11.2L vessel at 0o C is

An unknown compound ( A) has a molecular formula C4 H6. When (A) is treated with excess of Br2 a new substance (B) with formula C4H6 Br4 is formed. (A) forms a white ppt. with ammoniacal silver nitrate. Compound A is

Slowest step of the multistep reaction is known as

In the following reactions: Me−CH=CH−MeBr2−−−→CCl4A2NaNH2−−−−−→BNa/liq.NH3−−−−−−−→C The product(c) is:

Assume that a box full of electrons had a total charge of −96368 C. The number of moles of eletcrons present inside the box is Given:e=−1.6×10−19 C

Which of the following occurs in dark reaction of photosynthesis?

Two metallic oxides contain 27.6% and 30.0% oxygen respectively. If the formula of the first oxide is M3O4, then that of the second will be

CH3CH2ClNaCN−−−−→XNi/H2−−−−→YAcetic Anhydride−−−−−−−−−−→Z 'Z' in the above reaction sequence is

Give a chemical test to distinguish between the following pair of compounds 1: n-propyl alcohol and isopropyl alcohol 2: methanol and ethanol 3: cyclohexanol and phenol 4: propan-2-ol and 2 methylpropan-2-ol 5: phenol and anisole 6: ethanol and diethyl Ether

What is point mass and unit mass?

If 0.5 moles of BaCl2 is mixed with 0.2 moles ofNa3PO4 the maximum number of moles ofBa3(PO4)2 that can be formed

Cloud is a homogeneous or a heterogenous mixture

Select the WRONG pair regarding the relative contribution of various green-house gases.

Which of the given statement(s) about N, O, P and Q with respect to M is (are) correct?

Choose the products formed by action of Na2CO3 on H3BO3

In a semiconductor diode, p- side is earthed and to n-side is applied a potential of -2V: the diode shall

What is the decreasing order of strength of the bases OH−,NH−2,HC≡C⊝ and CH3−CH⊝2

Phosphoric acid (H3PO4) is prepared in a two-step process: (1) P4+5O2→P4O10 (2) P4O10+6H2O→4H3PO4 In step (1), 62 g of phosphorus is made to react with excess oxygen to form P4O10 with 85 % yield. In step (2), the yield of H3PO4 obtained is 90 %. Calculate the mass of H3PO4 produced.

The correct order of increasing basicity of the given conjugated bases is:

If temperature of a black body increases from 7o C to 287o C then the rate of energy radiation increases by

Does E2 reaction proceeds with 3°>2°>1° or 1°>2°>3° of alkyl halide.And what's the reason for it?