Which of these carbocations is most likely to form as an intermediate in an organic reaction? Justify your answer.

Identify the type of reaction in the following:

${\mathrm{C}}_3{\mathrm{H}}_7\mathrm{I}+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{C}}_3{\mathrm{H}}_7\mathrm{OH}+\mathrm{HI}$

Identify the type of reaction in the following:

${\mathrm{CH}}_3\mathrm{CHO}+2\left[\mathrm{H}\right]\to {\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{OH}$

Identify the type of reaction in the following:

${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{Br}\to {\mathrm{C}}_2{\mathrm{H}}_4+\mathrm{HBr}$

Identify the type of reaction in the following:

${\mathrm{C}}_2{\mathrm{H}}_4+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}$

Identify the type of reaction in the following:

${\mathrm{C}}_2{\mathrm{H}}_6+{\mathrm{Cl}}_2\to {\mathrm{C}}_2{\mathrm{H}}_5\mathrm{Cl}+\mathrm{HCl}$

Which one of the molecules below contains a chiral centre?