# Pka practice problems

Titration of a strong acid with a strong base is the simplest of the four types of titrations as it involves a strong acid and strong base that completely dissociate in water, thereby resulting in a strong acid-strong base neutralization reaction. This titration requires the use of a buret to dispense a strong base into a container of strong acid, or vice-versa, in order to determine the equivalence point. The purpose of a strong acid-strong base titration is to determine the concentration of the acidic solution by titrating it with a basic solution of known concentration, or vice-versa, until neutralization occurs.

As both the acid and base are strong high values of K a and K bthey will both fully dissociate, which means all the molecules of acid or base will completely separate into ions. The pH at the equivalence point for this titration will always be 7. In addition, the anion negative ion created from the dissociation of the acid combines with the cation positive ion created from the dissociation of the base to create a salt.

Therefore, the reaction between a strong acid and strong base will result in water and a salt. The acids and bases that are not listed in this table can be considered weak. Note that the strong bases consist of a hydroxide ion OH - and an element from either the alkali or alkaline earth metals.

An acid that is completely ionized in aqueous solution. This means when the strong acid is placed in a solution such as water, all of the strong acid will dissociate into its ions, as opposed to a weak acid. The general equation of the dissociation of a strong acid is:.

A base that is completely ionized in aqueous solution. This means when the strong base is placed in a solution such as water, all of the strong base will dissociate into its ions. The general equation of the dissociation of a strong base is:.

The first step in writing an acid-base reaction is determining whether the acid and base involved are strong or weak as this will determine how the calculations are carried out. For reactions with strong acid and strong base, the net ionic equation will always be the same since the acid and base completely dissociate and the resulting salt also dissociates. This leaves the final product to simply be water, this is displayed in the following example involving hydrochloric acid HCl and sodium hydroxide NaOH.

We can simplify this equation by writing the net ionic equation of this reaction by eliminating the reactants with state symbols that don't change, these reactants are known as spectator ions:.

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This formed the salt NaCl aqwhich isn't shown in the net ionic equation since it dissociates. The net ionic equation for a strong acid-strong base reaction is always:.

Therefore, this is a weak acid-strong base reaction which is explained under the link, titration of a weak acid with a strong base. Titration is a procedure for carrying out a chemical reaction between two solutions by the controlled addition from a buret of one solution into the other. A method, such as an indicator, must be used in a titration to locate the equivalence point. When titrating, acid can either be added to base or base can be added to acid, both will result in an equivalence point, which is the condition in which the reactants are in stoichiometric proportions.

They consume each other, and neither reactant is in excess. This reaction results in the production of water, which has a neutral pH of 7. The pH at the equivalence point is 7. Further adding acid or base after reaching the equivalence point will lower or raise the pH, respectively. How many liters of 3. Since we are given the molarity of the strong acid and strong base as well as the volume of the base, we are able to find the volume of the acid. The equation of the reaction is as follows:.

To find the volume of the solution of HI, we use the molarity of HI 3.Random Quiz. Can you pick the pKa values that go with each general or specific acid? Plays Quiz not verified by Sporcle. Quiz Rating Details. Rate 5 stars Rate 4 stars Rate 3 stars Rate 2 stars Rate 1 star. How to Play Forced Order. Also try: Functional Group Match. Questions Remaining 20 Correct 0 Wrong 0. You got. Prev Next.

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## Organic: Acid/Base Practice Problems

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Send Report.The latest addition to the Chemistry Steps Prime benefits is the Multiple-Choice Quizzes which are a fine way of checking and polishing your skills before the organic chemistry exam. So for the topics related to the first seven chapters have been added. It is a continuous work with the goal of having all the topics for Org 1 and 2 covered within the next few months.

There is also a summary guide of a practical approach to solving IR problems with a worked example following three important steps. These study guides are comprehensive and cover most of what is taught for that topic in undergraduate organic chemistry courses. Table of Content. Organic I and II. Geometry and Hybridization. Hybridization and Hybrid Orbitals: understand the bond types and angles as well as a shortcut to quickly determining the sp 3sp 2and sp hybridization.

One of the foundations and a key transition from General to Organic Chemistry is the deep insight of molecular structures and learning the concept of Bond-Lile Zig-Zag representation. Here is the much-needed to-the-point summary linking the Bond-line, Lewis and Condensed structures! Acids and Bases. Conformations of Alkanes and Cycloalkanes.

Stereochemistry and Chirality. Elimination Reactions — E1 and E2.

I know we all have to deal with this at one point. Yes, it is possible to summarize in one simple chart! Reactions of Alkenes. All the reactions of alkenesstarting from Addition of Hydrogen halide HXHydroboration-Oxidation, Ozonolysis and all the way to the Simmons—Smith reaction including the mechanism and the regio — and stereochemistry of the reaction where it is applicable.

Reactions of Alkynes. Just like for the alkenes, a summary and the mechanisms of all the reactions includinghydration, hydrohalogenation, hydroboration, reduction and oxidative cleavage, plus the acid-base chemistry of terminal alkynes and their synthetic applications. Reactions of Alcohols. Save the time to looking them up one-by-one!

Additionally, you will have the summary of preparing alcohols By Addition Reaction to Alkenes and Substitution Reactions. Alcohols in Substitution and Elimination Reactions. This will cover the reactions where the alcohols are nucleophiles, electrophiles, and bases. A sum up for the approaches for converting the OH into a good leaving group and using it to prepare alkenes by Zaitsev and Hoffman reactions. The Diels-Alder Reaction. Diels-Alder reaction summarized in two comprehensive pages.To determine the net charge on a protein you have to know the amino acid sequence and understand the charges on each amino acid residue in the amino acid sequence.

To do this, you have to know the charge on each weak acid on the protein before and after dissociation. You also have to know the pH of the solution and the pKa of each weak acid on the protein. You learned all this in previous objectives 1, 10, and What is the approximate pKa for all alpha-amino groups and for all alpha-carboxyl groups?

What are the pKa's for the R-groups of aspartic acid, glutamic acid, histidine, lysine, and arginine? Given the pH, predict whether the alpha-amino and alpha-carboxyl groups and the R-groups of the amino acids aspartic acid, glutamic acid, histidine, lysine, and arginine would be neutral or would carry a net negative or net positive charge Given the written sequence for a protein, be able to identify the amino-terminus, the carboxyl-terminus, and the R-groups for each residue.

The other alpha-amino and alpha-carboxyl groups were used to make polypeptide bonds and no longer exist. The amino terminus has a pka of about 9 so it is positively charged. The carboxy terminus has a pKa of about 2 so it is negatively charged. The R-Groups of both aspartic acid and glutamic acid have a pKa of about 4 so they are both negatively charged.

So, there are a total of two positive charges, one contributed the alpha amino alanine and one contributed by the R-group of lysine. And, there are a total of four negative charges, one from the alpha-carboxy of aspartate, two from the R-groups of aspartate, and one from the R-group of glutamate.

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The only available alpha-amino group and alpha-carboxyl group are on the amino-terminus and the carboxy-terminus respectively. So, there are a total of three positive charges, one contributed the alpha amino alanine and two contributed by the R-groups of arginine.

And, there are a total of two negative charges, one from the alpha-carboxy of glycine and one from the R-group of glutamate.What is the most acidic group of protons on methyl acetate? This is a flammable liquid with a smell reminiscent of some glues and nail polish. Which of the following is the strongest base? Heartburn is caused by a buildup of excessive amounts of stomach acid, particularily HCl. This acid is used to digest the food we eat, but it can often back up into the esophagus causing that burning sensation many of us are familiar with.

The symptoms of heartburn can be treated with a mild base, which acts to neutralize the excess HCl. For example, Tums is a very commonly used antacid that can be bought over the counter. Other antacids, such as Alka Seltzer, work in similar ways.

### Acid Base Practice Problems Quiz

Below, show the mechanism and products for reaction in which calcium carbonate the active ingredient in Tums neutralizes HCl in a simple proton transfer reaction. Following this acid-base reaction, carbonic acid quickly degrades into CO 2 and H 2 O. Using the concept of resonance delocalization of charge, find which compound is the stronger base. List the following carboxylic acids in order of decreasing acidity. How does the presence of an electronegative substituent such as Cl affect the acidity of a carboxylic acid? How does the location of the substituent affect the acidity of the carboxylic acid? Which compound has the lower pK a? At what pH will alanine have no net charge the amount of negative charge will be the same as the amount of positive charge? Indicate the order of acid strength of these compounds by ranking 1 being the strongest acid :.

Indicate the order of base strength of these compounds by ranking 1 being the strongest base :.Use the Henderson-Hasselbalch equation:. We want the ratio of acid to conjugate base, which would be the reciprocal.

NaOH is added to a mL of 2M acetic acid. If the pK a value of acetic acid is approximately 4. We can ignore water and sodium ions for the sake of this question. The reactants exist in a ratio, so that for every mol of NaOH we add, we lose one mol of acetic acid and gain one mol of acetate.

If we use the Hendersen Hasselbach equation we can see that the pH equals the pK a when the concentration of conjugate base acetate equals the concentration of acid. If we have 1mol of acetic acid and add 0. We will then be at a point where acetic acid equals acetate. This is summarized in the ICE table below. Now we know the moles of NaOH 0. The K a for HCN is. To answer this question, we need to be able to compare the concentrations of acid and conjugate base in the solution with the pH.

The Henderson-Hasselbach equation is used to compare these values, and is written as:. In this question, this equation can be written with the given values of K a and pH.

### Titration of a Strong Acid With A Strong Base

As a result, we want to see to it that the amount of conjugate base is equal to the concentration of acid, so that. You need to produce a buffer with pH of. You have a solution with of acetic acid.

How many moles of sodium acetate must you add to achieve the desired pH? Assuming that these ions occupy the same volume. We know we have 30g of acetic acid, which is equal to 0. Plugging in our values gives us. If sodium hydroxide is slowly added to this solution, what will the pH be at the half equivalence point? If we use the Henderson-Hasselbalch equation, we do not need to worry about using the molar amounts of both the acid and the base.

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At the half equivalence point, the conjugate base concentration is equal to that of the weak acid. The ratio given in the question isor. To use the correct ratio for the Henderson-Hasselbalch equation, we need to convert this ratio to its reciprocal:.

The question is asking for the concentration of hydrogen ions.Henderson-Hasselbalch equation is a numerical expression which relates the pH, pKa and B uffer Action of a buffer. A buffer is a solution which can resist the change in pH. In the previous post, we have discussed the Titration Curve of a weak acid and the Derivation of Henderson-Hasselbalch Equation. The characteristic shape of the titration curve of a weak acid is also described by the Henderson-Hasselbalch equation.

In this chapter we will discuss the methods to calculate the pH or pKa of a buffer using Henderson-Hasselbalch equation using sample problems. Henderson-Hasselbalch Equation is given as:. Problem A mixture of 0. Calculate the pH of the medium if the pKa of the acetic acid is 4. This is a straight question and you can directly apply the Henderson-Hasselbalch equation. All the required components to calculate the pH are given in the question itself.

Following components are given in the question:. Answer: The pH of the given solution is 4. Problem The pH of the given solution of lactic acid and lactate is 4. Calculate the pKa of lactic acid, when the concentration of lactic acid and lactate are 0.

We need to calculate the pKa of lactic acid. So, take out the pKa to the left side and the equation now becomes:. Answer: The pKa of the given solution is 3. Problem What is the ratio of the concentration of acetic acid and acetate ions required to prepare a buffer with pH 5. The pKa of acetic acid is 4. You cannot direct apply the Henderson-Hasselbalch equation here because it is an indirect question.

First you need to rearrange the equation accordingly. Answer: The ratio of acetate to acetic acid required to get a pH of 5. Study Offline Without Internet. The PDF file will be opened in a new window in the browser itself.