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Question: If you visit a gym or fitness center, you will notice that some people are stronger than others. The...

If you visit a gym or fitness center, you will notice that some people are stronger than others. There is a similar situation in the world of acids and bases. Some are stronger than others. For example, HFHF is classified as weak acid and HClHCl is a strong acid.
Which of the following statements gives the best explanation for this difference in acid strength?
A.The molar mass of HFHFis less than the molar mass of HClHCl
B.The HFH - Fbond requires more energy to break than the HClH - Clbond.
C.A solution of 1 M HFHF has a lower pH than a solution of 1M HClHCl.
D.The solubility of HFHFin water is less than the solubility of HClHCl in water.

Explanation

Solution

Acid are those substances which give out Hydrogen ion i.e. H+{H^ + } when dissolved in a solution and stronger will be the one which gives out hydrogen ions faster and easily. If the bond is breaking easily, then it will give out the ion very easily. So, these factors can decide which one will be stronger and which is not.

Complete step by step answer:
In the given question, the two acids i.e. HFHF and HClHCl are compared and we have to explain the acidic strength of both the acids i.e. which one is stronger and why.
An acid is a substance which gives out Hydrogen ions i.e. H+{H^ + } ions in the solution when it is dissolved and the base is a substance which gives out OHO{H^ - } ions when dissolved in a solution. In the given question, we see that both contain Hydrogen, so they will give Hydrogen ions when they will be dissolved in the solution. Hence, they will act as an acid.
Now both are acids, the stronger acid will be the one which can give out Hydrogen ion (H+)\left( {{H^ + }} \right) more easily as compared to others.
In this case, HClHCl will give more fast and easily hydrogen ions as compared to HFHF and therefore will be the stronger acid.
This is because as we move down from Fluorine to Bromine (in the halogen family) the atomic size goes on increasing and therefore, the bond strength between Hydrogen and Halogen atoms will decrease because they will move apart and become weaker.
Bond strength 1Bond lengthBond{\text{ }}strength{\text{ }} \prec \dfrac{1}{{Bond{\text{ }}length}}
When the bond strength between the two is decreasing, it will break the bond i.e. Hydrogen-Halogen bonds more easily (because the distance is more and strength is weak) so which will ultimately release H+{H^ + } ion.
So, ClCl has a bigger size than FF, so HClH - Cl bonds will break more easily and therefore will release Hydrogen ions in solution more readily compared to HFHFand therefore, will become stronger acid.

So, the correct answer is B.

Note:
In the laboratory, it is warned not to use HFHF because it is very corrosive in nature which can dissolve any metal or substance in it. Though it is less acidic, it is very corrosive (there is a difference between being acidic and corrosive). There are other properties of halogen also like electron gain enthalpy, ionization energy etc. and also Fluorine is considered as the most electronegative element of the periodic table.