We must use this concentration as the starting concentration of ammonium ion in

# We must use this concentration as the starting

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. We must use this concentration as the starting concentration of ammonium ion in our equilibrium table. The equilibrium expression is Initial concentration ( M ) 0.0500 0 0 Change in concentration ( M ) –x +x +x Equilibrium concentration ( M ) 0.0500 – x x x NH 4 + ( aq ) + H 2 O( l ) NH 3 ( aq ) + H 3 O + ( aq ) K a = [NH 3 ][H + ] [NH 4 + ] = 5.6×10 -10 = ( x )( x ) 0.0500 – x x = = 5.3×10 -6 M = [H + ] 11 10 8 . 2 x 2 0.0500 pH = –log(5.3×10 -6 ) = 5.28
Acid-Base Titrations Acid-Base Titrations The equivalence point in a titration can be visualized with the use of an acid-base indicator. The endpoint of a titration is the point at which the color of the indicator changes. HIn( aq ) H + ( aq ) + In ( aq )
Acid-Base Titrations Acid-Base Titrations
Acid-Base Titrations Acid-Base Titrations
Worked Example 17.6 Strategy Determine the pH range that corresponds to the steepest part of each titration curve and select an indicator (or indicators) that changes color within that range. Which indicator listed in Table 17.3 would you use for the acid-base titrations shown in (a) Figure 17.3, (b) Figure 17.4, and (c) Figure 17.5? Solution (a) The titration curve at right is for the titration of a strong acid with a strong base. The steep part of the curve spans a pH range of about 4 to 10. Most of the indicators in Table 17.3, with the exceptions of thymol blue, bromophenol blue, and methyl orange, would work for the titration of a strong acid with a strong base.
Worked Example 17.6 (cont.) Solution (b) The figure at right shows the titration of a weak acid with a strong base. The steep part of the curve spans a pH range of about 7 to 10. Cresol red and phenolphthalein are suitable indicators. (c) The figure at right shows the titration of a weak base with a strong acid. The steep part of the curve spans a pH range of 7 to 3. Bromophenol blue, methyl orange, methyl red, and chlorophenol blue are all suitable indicators.
Solubility Equilibria Solubility Equilibria Quantitative predictions about how much of a given ionic compound will dissolve in water is possible with the solubility product constant, K sp . 17.4 AgCl( s ) Ag + ( aq ) + Cl ( aq ) K sp = [Ag + ][Cl ] Compound Dissolution Equilibrium K sp Aluminum hydroxide Al(OH) 3 ( s ) Al 3+ ( aq ) + 3OH ( aq ) 1.8 x 10 –33 Calcium fluoride CaF 2 ( s ) Ca 2+ ( aq ) + 2F ( aq ) 4.0 x 10 –11 Silver bromide AgBr( s ) Ag + ( aq ) + Br ( aq ) 7.7 x 10 –13 Silver chloride AgCl( s ) Ag + ( aq ) + Cl ( aq ) 1.6 x 10 –6 Zinc sulfide ZnS( s ) Zn 2+ ( aq ) + S 2– ( aq ) 3.0 x 10 –23
Solubility Equilibria Solubility Equilibria Molar solubility is the number of moles of solute in 1 L of a saturated solution (mol/L) Solubility is the number of grams of solute in 1 L of a saturated solution (g/L). To calculate a compound’s molar solubility: 1) Construct an equilibrium table. 2) Fill in what is known.

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