We’re being asked to identify which among the given acids is strong or weak.
Weak acids are weak electrolytes that don’t completely ionize but instead reach a state of equilibrium.
However, it’s easier to identify strong acids than familiarize yourself with all the weak acids (since the common strong acids have rules and are relatively fewer).
Strong acids are considered strong electrolytes. They completely dissociate into ions when dissolved in water.
• Strong binary acids – paired with a highly electronegative atom
Strong binary acids are: HCl, HBr, and HI
• Strong oxyacids (or oxoacids) - have 2 or more oxygens than hydrogens
Oxyacids → possess H+ ion, connected to nonmetal and oxygen
Common strong oxyacids are: HNO3, HClO3, HClO4, H2SO4
Exceptions to the rule are: Oxalic acid (H2C2O4) and Iodic acid (HIO3)
▪ both have 2 more O than H but are weak acids because carbon and iodine have low electronegativity
The Ka expression for a weak acid (HA) is:
Note that each concentration is raised by the stoichiometric coefficient: [HA], [H3O+] and [A–] are raised to 1.
classify each of the following acids as strong or weak. If the acid is weak, write an expression for the acid ionization constant (Ka).
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