5._Chapter_18_acid_base

5._Chapter_18_acid_base - Common-Ion Effect in Acid-Base...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
Common-Ion Effect in Acid-Base Equilibria Common-Ion Effect: is the shift in equilibrium caused by the addition of a compound having an ion in common with the dissolved substance. Consider the ionization of a weak acid, HA: HA(aq) + H 2 O(l) A¯(aq) + H 3 O + (aq) According to Le Chatelier’s principle, the addition of A¯ (e.g. in the form NaA) or H 3 O + (e.g. In the form HCl or HNO 3 ) causes the equilibrium to shift to the left. In the presence of excess strong acid or excess A¯, the ionization of a weak acid HA is significantly suppressed. Similarly, the ionization of a weak base (B) is suppressed significantly in the presence of excess HB + or strong base.
Background image of page 1

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

View Full DocumentRight Arrow Icon
Example Calculate the percent ionization of CH 3 COOH in each of the following solutions. a) 1.0L if 0.125 M CH 3 COOH (aq) (K a = 1.8 x 10 -5 ) b) 1.0L if 0.125 mol CH 3 COOH and 0.025 mol CH 3 COONa
Background image of page 2
Acid-base Neutralization reactions In an acid-base neutralization reaction, an acid and a base react in aqueous solution to produce a salt. Sometimes water is also produced. HCl (aq) + NaOH (aq) HF (aq) + NaOH (aq) We are especially interested in neutralization reactions that involve a strong base, an strong acid, or both. If a least one of the reactants is a strong acid or a strong base, then we can safely assume (usually!) that the neutralization goes to completion. How do we know that the reaction between weak acid and a strong base goes to completion? Because the equilibrium constant for the neutralization reaction (K neutr ) is very large. HCl (aq) + NaOH (aq) H 2 O (l) + NaCl (aq) Because HCl (aq) + NaOH (aq) completely dissociates the net equation for the neutralization reaction is H 3 O + (aq) + OH¯ (aq) 2 H 2 O (l) If we mix equal moles of HCl (aq) and NaOH (aq) the concentration of H 3 O + and OH¯ in the remaining NaCl solution after neutralization will be the same as those of pure water. Thus the reaction is the reverse of the dissociation of water, K n (‘n’n for neutralization) is just the reciprocal of the ion product for water K n = 1/K w 14 14 w 3 1x10 1x10 1 K 1 ] ][OH O [H 1 = = = = - - + n K H 3 O + (aq) + OH¯ (aq) 2 H 2 O (l)
Background image of page 3

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

View Full DocumentRight Arrow Icon
HF (aq) + OH¯ (aq) A¯(aq) + H 2 O (l) HF (aq) + NH 3 (aq)
Background image of page 4
When we mix a weak acid and a strong base, we know that the neutralization will go to completion. The pH of the solutions is determined by what’s left behind by the neutralization reaction. Similarly,
Background image of page 5

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

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 22

5._Chapter_18_acid_base - Common-Ion Effect in Acid-Base...

This preview shows document pages 1 - 6. Sign up to view the full document.

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