Which step is chain propagation step in the following mechanism?

$\left(\mathrm{i}\right) {\mathrm{Cl}}_2\stackrel{h\nu }{\to }{\mathrm{Cl}}^{\bullet }+{\mathrm{Cl}}^{\bullet }$
$\left(\mathrm{ii}\right) {\mathrm{Cl}}^{\bullet }+ {\mathrm{CH}}_4\to \stackrel{\bullet }{{\mathrm{CH}}_3}+ \mathrm{HCl}$
$\left(\mathrm{iii}\right){\mathrm{Cl}}^{\bullet }+{\mathrm{Cl}}^{\bullet }\stackrel{}{\to }{\mathrm{Cl}}_2$
$\left(\mathrm{iv}\right)\stackrel{\bullet }{{\mathrm{CH}}_3}+ \mathrm{HCl}\to {\mathrm{CH}}_3\mathrm{Cl}$

1. (i)

2. (ii)

3. (iii)

4.  (iv)

S_N1 mechanism for the reaction,

R-X+KOH$\to$ROH+KX follow:

(1) carbocation mechanism

(2) carbanion mechanism

(3) free radical mechanism

(4) either of these

The elimination reaction among the following is:

1. CH₃CH₃+Cl₂$\to$CH₃CH₂Cl+ HCl

2. CH₃Cl+ KOH(aq.) $\to$CH₃OH +KCl

3. CH₂=CH₂ +Br₂ $\to$CH₂BrCH₂Br

4. C₂H₅Br+ KOH(alc.) $\to$C₂H₄ + KBr+H₂O

Which of the following is an example of the elimination reaction?

(1) Chlorination of methane

(2) dehydration of ethanol

(3) nitration of benzene

(4) hydroxylation of ethylene

The formation of cyanohydrin from a ketone is an example of:

(1) electrophilic addition

(2) nucleophilic addition

(3) nucleophilic substitution

(4) electrophilic substitution

The compound which reacts with HBr obeying Markownikoff's rule is:

1. $C{H}_2=C{H}_2$   

2. 

3. 

4. 

If X is halogen the correct order for S_N2 reactivity is-

1. R₂CHX > R₃CX > RCH₂X

2. RCH₂X > R₃CX > R₂CHX

3. RCH2X > R₂CHX > R₃X

4. R₃CX > R₂CHX > RCH₂X

Consider the following bromides:

the correct order of S_N1 reactivity is:

1. A>B>C

2. B>C>A

3. B>A>C

4. C>B>A

In an S_N1 reaction on chiral centres there is

1. 100% racemisation

2. inversion more than retention leading to partial racemisation

3. 100% retention

4. 100% inversion

Which step is the chain termination step in the following mechanism?

$\left(\mathrm{i}\right) {\mathrm{Cl}}_2\stackrel{h\nu }{\to }{\mathrm{Cl}}^{\bullet }+{\mathrm{Cl}}^{\bullet }$
$\left(\mathrm{ii}\right) {\mathrm{Cl}}^{\bullet }+ {\mathrm{CH}}_4\to \stackrel{\bullet }{{\mathrm{CH}}_3}+ \mathrm{HCl}$
$\left(\mathrm{iii}\right)\stackrel{\bullet }{\mathrm{C}}{\mathrm{H}}_3+{\mathrm{Cl}}_2\to {\mathrm{CH}}_3\mathrm{Cl}+{\mathrm{Cl}}^{\bullet }$
$\left(\mathrm{iv}\right){\mathrm{Cl}}^{\bullet }+\stackrel{\bullet }{\mathrm{C}}{\mathrm{H}}_3\to {\mathrm{CH}}_3\mathrm{Cl}$

1. (i)

2. (ii)

3. (iii)

4. (iv)