Consider each acid formula starts with hydrogen then has a non-metal element and sometimes oxygen. Consider the location of these non-metals (not oxygen) on the periodic table. Describe the...
Consider each acid formula starts with hydrogen then has a non-metal element and sometimes oxygen. Consider the location of these non-metals (not oxygen) on the periodic table. Describe the link between the position of the non-metal and acid strength.
Acids under question, Hydrochloric, Sulfuric and Phosphoric Acid.
Thanks for future help.
For the acids in question (hydrochloric acid, sulfuric acid and phosphoric acid), the corresponding non-metals are period 3 elements (chlorine, sulfur and phosphorus).
The acid strength of non-metal hydrides is a function of two characteristics: polarity of X-H bonds and strength of H-X bond. Polarity is a function of electronegativity of non-metal and increases with an increase in electronegativity. Higher electronegativity means easy dissociation of electrons from hydrogen and thus easier transfer of protons (H+). Therefore, higher electronegativity causes higher acid strength. The atomic radius governs the strength of H-X bond, the greater the radius of the non-metal atom, the easier it is to break the hydrogen atom away from it. Hence, a larger atomic radius results in lower bond-strength and higher acidic strength.
In the given case, acid strength varies as hydrochloric acid>sulfuric acid>phosphoric acid. Electronegativity also varies as Cl>S>P, while the atomic radius varies as Cl<S<P. Hence, the atomic radius reduces the acidic strength, while electronegativity increases it as we move from phosphorus to chlorine. However, the smaller change in atomic radius is insignificant when compared to a large change in electronegativity and hence the acidic strength increases as we go across the row (from P to Cl).