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Chemistry I - Buffers and Titrations

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Section 1

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What occurs when pH=pKa of a weak acid buffer?

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6 years ago

Date created

Mar 1, 2020

Cards (16)

Section 1

(16 cards)

What occurs when pH=pKa of a weak acid buffer?

Front

[weak acid] = [conjugate base]

Back

Where is the equivalence point for monovalent strong acid and base titrations ALWAYS?

Front

At pH=7

Back

How should an indicator for a particular titration be chosen?

Front

It should have a pKa relatively close to the equivalence point of the reaction

Back

Where will the equivalence point be of a weak base titrand and strong acid titrant?

Front

It will be in the acidic side (lower than pH=7)

Back

What is the effective range of a buffer?

Front

About ±1 of the pH scale

Back

T/F The equivalence point is where [HA]=[A-]

Front

F This is where the moles of acid equal the moles of base added (to neutralize)

Back

Where should the equivalence point of a titration of HClO₄ and NaOH?

Front

Since perchloric acid and sodium hydroxide are strong acids and bases, respectively, they will have an equivalence point of ≈ pH=7.

Back

Differentiate between titrant, titrand, and equivalence point.

Front

The titrant is a solution with known concentration we are ADDING to the titrand, which has an unknown concentration. The equivalence point is the completion of the reaction.

Back

For a titrand of NaOH and titrant of HCl, what will be the species at the equivalence point?

Front

NaCl and H₂O

Back

How many equivalent points will a titration of an amino acid have?

Front

Three (if has an acid or basic side chain)

Back

T/F Where the indicator changes color is known as the equivalence point.

Front

F This is the endpoint of the titration.

Back

What, in general, is the purpose of a buffer?

Front

It resists small additions of acid or base by limiting the change of the pH

Back

What would change if the ratio of weak acid/conjugate base was doubled in a buffer?

Front

The buffering capacity of the system would double!

Back

What is a buffer composed of? What are two common buffers tested on the MCAT

Front

A mixture of a weak acid/base and its salt Acetic acid and sodium acetate Ammonia and ammonium chloride

Back

What are the two primary methods to determining what type of titration is being shown in a graph?

Front

Determine where the pH begins (if it is near 7, is most likely weak, above or below, strong), and then determine where the equivalence point is.

Back

Where will the equivalence point of a titration of acetic acid and NaOH be in comparison to an HCl and NaOH titration?

Front

It will be more BASIC, as there will be a greater concentration of hydroxide ions than hydrogens ions at equilibrium due to the common ion effect and autoionization of water.

Back