SASBWAWB - Lab Activity: Strong Acids & Strong Bases,...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Lab Activity: Strong Acids & Strong Bases, Weak Acids & Weak Bases, and the Hydrolysis of Salts Strong acids and strong bases completely ionize in water to make hydronium or hydroxide ions. Because the reactions essentially result in 100% ionization, the [H 3 O + ] and the [OH ] can be calculated directly from the initial concentrations of the acid or base. Consider nitric acid, HNO 3 , and potassium hydroxide, KOH. HNO 3 + H 2 O Æ H 3 O + + NO 3 KOH Æ K + + OH [ H 3 O + ] soln = [HNO 3 ] 0 [ O H ] soln = [KOH] 0 On the other hand, weak acids and bases do not fully dissociate or ionize when they are in water. The pH of a solution of a weak acid or weak base must be predicted based on their dissociation constants: Ka or Kb. For an acid dissociation, consider hypochlorous acid, HClO. HClO + H 2 O Ù H 3 O + + ClO 2 This reaction does not go to completion, therefore [H 3 O + ] soln [HClO] 0 . Therefore, we must apply the equilibrium condition and use Ka to calculate the [H 3 O + ] of the solution. The pH can then be calculated as the log[H 3 O + ] A weak basic solution, like methylamine will not fully ionize water into hydroxide ions, but instead, an equilibrium is established: CH 3 NH 2 + H 2 O Ù CH 3 NH 3 + + OH The [OH ] soln [CH 3 NH 2 ] 0 . The hydroxide ion concentration must be calculated using K b and the application of the equilibrium condition. The hydronium ion concentration and the pH can then be calculated. Some salts exhibit acidic or basic properties based on the identities of their cations or anions. Other salts are completely neutral when dissolved in water. Consider KNO 3 . When KNO 3 is dissolved in pure water, the pH of the solution will be neutral (7). This is because K+ is the conjugate acid of a very strong base, KOH. Therefore, the following reaction simply does not occur:
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 8

SASBWAWB - Lab Activity: Strong Acids & Strong Bases,...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online