[NaOH – Caustic soda, KOH – Caustic potash, HCl-Hydrochloric acid, H2SO4- Sulfuric acid]
All answers are in the periodic table.
Sodium Hydroxide (NaOH) and Potassium Hydroxide (KOH) are almost interchangeable. They are the most chemically similar to hydroxides. They are both a white, strongly alkaline, corrosive solid or powder. Sodium Hydroxide is more commonly known as lye or caustic soda where Potassium Hydroxide is known as potash.
NaOH vs KOH which is stronger?
Both KOH and NaOH are fully ionic strong bases.
At equivalent concentrations, there is no difference in base strength when they exist as a dilute solution. In either case, they dissociate in water completely and they both produce the same base, OH-. OH- is OH-. Consequently, the pH of, for example, a 0.1 M solution of NaOH should be the same as a 0.1 M solution of KOH.
pH = 14- pOH
pOH = -log [OH-]
pOH = -log (0.1) = 1
pH = 14-1 = 13
NaOH vs KOH: which is stronger as commercially available solid or 45-50% liquid?
A strong base is a base that is completely dissociated in an aqueous solution like NaOH and KOH. In contrast, a weak base only partially dissociates into its ions in water. Ammonia is a good example of a weak base.
The question is which is stronger? The answer is one that loses -OH ion quicker in water. In the periodic table, Na and K both belong to group 1. Na atomic number is 11 while K’s atomic number is 19. K is a bigger atom than Na. In a group in the periodic table, an increase in the size of elements outweighs increasing nuclear charge. The electron configuration of Na is 2,8,1, there is a total of 11 electrons spread over three energy subshells. The electron configuration of K is 2,8,8,1, there is a total of 19 electrons spread over four energy subshells. While both have one electron in the outer valency shell. K has one full extra energy subshell because of its higher atomic number 11 [Na] vs 19[K]. A larger number of inner electrons in K produces larger electron to electron repulsion [same charge] to outer valency electron making it less attracted to protons in the nucleus and thus outer valency electron of K gets pushed out more easily and gets ejected out. This makes K ionizes more easily than Na. The ionization energy of Na is 495.8 kj/mol vs K has 418.8 kj/mol. Na needs more energy to ionize. Therefore, K is more electro +ve /reactive than Na. This makes KOH losing OH- ion more easily than Na and a stronger base.
HCl vs H2SO4: Which is stronger? 35% HCl or 98% H2SO4?
Both HCl and H2SO4 are strong acids
The strength of an acid as a molecule is its ability to lose a proton, H+ ion in water. In HCl, the bond dissociation enthalpy is 427 kJ/mol whereas in H2SO4, where the O – H bond breaks, it is 467 kJ/mol. Lower bond dissociation enthalpy of the H – Cl bond makes it lose proton more easily than H2SO4. That makes HCl stronger than H2SO4 as a molecule.
35% HCl vs 98% H2SO4: Which is more harmful to human safety
When Human safety with these acids arises, it does not matter which has lower or higher bond strength.
Commercially H2SO4 is 98% acid and HCl is 35% acid. H2SO4 has just only 2% water. H2SO4 molecule has two O-H bonds. Hydrogen attached to oxygen makes it an obvious candidate for hydrogen bonding. H2SO4 is hygroscopic. H2SO4 has a strong affinity for water. If you put sulfuric acid on your skin, the first thing it will do is dehydrate you. This has the effect of carbonizing your skin giving you 3rd-degree burns. Then, the water taken from your skin allows the H2SO4 to dissociate and the concentrated acid burns your skin.
In short, though HCl has an H atom, it does not form a hydrogen bond. Also, commercial HCl at 35% concentration has plenty of water.
From a Human safety point, H2SO4 is far more dangerous than HCl.
Credit: Pub Chem for the periodic table image