Question

The correct order of reactivity of hydrogen halides with ethyl alcohol is:
\[
  A.{\text{ }}HF > HCl > HBr > HI \\
  B.{\text{ }}HCl > HBr > HF > HI \\
  C.{\text{ }}HBr > HCl > HI > HF \\
  D.{\text{ }}HI > HBr > HCl > HF \\
 \]

Answer 1

Hint: In order to solve the given problem and find the correct order of reactivity of the hydrogen halides with the ethyl alcohol first we will study briefly about different factors over which the reactivity of the hydrogen halide depends. We will see the trend or the increasing and the decreasing order of those characteristics. Further on the basis of the factors we will select the correct order of the reactivity of hydrogen halide with ethyl alcohol.


Complete step by step answer:
Hydrogen halide is the compound in which a halogen is attached with a hydrogen element. The elements like fluorine, chlorine, iodine etc are referred to as halogen.
The reactivity of hydrogen halide with ethyl alcohol or any other compounds depends on various factors, some of them are:
Stability of hydrogen halide bond.
Size of the halide atom
Bond dissociation energy
But all of the above factors are dependent on the size of the halide.
So first let us see the halide atom from smallest to largest.
The trend of the size of the atom is:
\[F < Cl < Br < I\]
The size of fluorine is the smallest amongst these and the size of the iodine is the largest amongst all.
Due to the largest size of the iodine and small size of the hydrogen atom, the size of the hydrogen iodide bond is large. Due to this large size of the bond between hydrogen and iodine the bond is unstable and also the bond dissociation enthalpy is the lowest.
Whereas the size of fluorine atom is the smallest and so, the bond length of the hydrogen fluoride bond is lowest and the bond dissociation enthalpy is the largest.
Due to high bond dissociation enthalpy the smaller atom hydrogen halide will have lower reactivity as compared to the large sized hydrogen halide. And so on the basis of the size we have the correct order of reactivity as:
\[HF < HCl < HBr < HI\]
Hence, the correct order of reactivity of hydrogen halides with ethyl alcohol is \[HI > HBr > HCl > HF\]
So, the correct answer is “Option D”.

Note: In order to solve the given problem students must remember the order in which the atoms are present in the periodic table in order to have a brief idea about the size of the atom relative to the other atoms. In order to solve such problems students must consider different points and should not infer the solution with just one point. Hydrogen halides with the formula HX are diatomic inorganic compounds where X is one of the halogens: fluorine, chlorine, arsenic, bromine, or astatine. Hydrogen halides are gases that are dissolved in water to produce acids usually referred to as hydrohalic acids.