A buffer solution is prepared by adding 5.50 g of ammonium chloride and 0.0188 mol of ammonia t

step 1 So we are given 5 .50 grams of ammonium chloride. And we also know that we have 0 .0188 moles of

A buffer solution is prepared by adding 5.50 g of ammonium...

A buffer solution is prepared by adding $5.50 \mathrm{~g}$ of ammonium chloride and 0.0188 mol of ammonia to enough water to make $155 \mathrm{~mL}$ of solution. (a) What is the pH of the buffer? (b) If enough water is added to double the volume, what is the $\mathrm{pH}$ of the solution?

A buffer solution is prepared by adding $5.50 \mathrm{~g}$ of ammonium chloride and 0.0188 mol of ammonia to enough water to make $155 \mathrm{~mL}$ of solution.
(a) What is the pH of the buffer?
(b) If enough water is added to double the volume, what is the $\mathrm{pH}$ of the solution?

Key Concepts

Buffer Solutions

A buffer solution is a mixture that resists changes in pH when small amounts of acid or base are added. It typically consists of a weak acid and its conjugate base or a weak base and its conjugate acid. This stability is due to the equilibrium that shifts slightly in one direction or the other to counteract pH changes, thereby maintaining a relatively constant pH level.

Conjugate Acid?Base Pair

A conjugate acid-base pair consists of two species that transform into each other by the gain or loss of a proton. In buffer solutions, the weak base and its conjugate acid (or weak acid and its conjugate base) coexist in equilibrium. This pair is essential for the buffer’s ability to neutralize added acids or bases through reversible proton transfer reactions.

Henderson–Hasselbalch Equation

The Henderson–Hasselbalch equation provides a way to calculate the pH of a buffer solution using the pKa (or pKb) and the ratio of the concentrations (or moles) of the conjugate base and acid. It expresses the relationship between the pH and the logarithm of the concentration ratio, making it a powerful tool for understanding and designing buffer systems.

Effect of Dilution on Buffers

When a buffer solution is diluted, the concentrations of both the weak acid (or weak base) and its conjugate partner decrease proportionally. Since the buffer pH depends on the ratio of these concentrations rather than their absolute values, diluting a buffer generally has a minimal effect on its pH. This property is one of the defining characteristics of buffer systems.

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