Name: titration curves and ph changes
Uploaded: 2024-04-04T10:51:19.000Z
Duration: 1 min 26 s
Channel: JoVE

K12 Standards

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North Carolina K-12 Science Standard Course of Study

9-12

Chemistry

Matter and its Interactions

PS.Chm.6.3

Acid&#8211;Base Titration: Overview

Acid-base titration can be performed to determine an unknown concentration of acid using a known concentration of a base or vice versa.&#160;
When titrating an acid with a base, the titrant is gradually added to the acid, raising the pH. The pH change is plotted against the volume of the base to create a titration or pH curve.
The titration curves are S-shaped, though differences exist depending on whether the acid is strong or weak.
The pH at the start of the titration will be acidic but higher for a weak acid, assuming equal initial concentrations of acid.
The equivalence point is the point on the titration curve at which the moles of base equals the moles of acid in solution.
In the case of a strong acid, the equivalence point is reached when a strong base neutralizes all the hydronium ions produced by the strong acid; therefore, it always occurs at pH 7.
In contrast, a weak acid&#39;s equivalence point occurs at a pH greater than 7 and is reached when all the weak acid is converted into its conjugate base.
Near the equivalence point, there is a sudden jump in the pH of the solution. However, in a weak acid titration, this rapid pH shift is not as steep as in a strong acid titration.

zuur-base-titratiecurven

Een zuur-base-titratie is een techniek die wordt gebruikt om de concentratie van een onbekend zuur of een onbekende base te bepalen, met behulp van een titrant met een bekende concentratie: een base voor zuurtitratie of een zuur voor base titratie. Het proces omvat het geleidelijk toevoegen van de titrant, wat leidt tot een voorspelbare verandering in de pH van de oplossing. Deze verandering wordt uitgezet op een titratiecurve, die laat zien hoe de pH van een oplossing varieert met de toegevoegde hoeveelheid titrant. Dergelijke curven zijn behulpzaam bij het monitoren van de voortgang van de titratie en het identificeren van het eindpunt.

Titratiecurven kunnen in verschillende combinaties worden gevormd: tussen sterke zuren en sterke basen, sterke zuren en zwakke basen, of zwakke zuren en sterke basen. Deze curven vertonen doorgaans een S-vorm, maar hun specifieke kenmerken variëren afhankelijk van de sterkte van het betrokken zuur of de base. Voor sterke zuren die door sterke basen worden geneutraliseerd, wordt het equivalentiepunt, waar het aantal mol zuur gelijk is aan het aantal mol base, bereikt bij een pH van 7, wat wijst op volledige neutralisatie. In het geval van zwakke zuren ligt dit equivalentiepunt boven pH 7, wat de transformatie van het zwakke zuur in zijn geconjugeerde base weerspiegelt. Bij sterke zuur titraties verandert de pH significanter nabij het equivalentiepunt dan bij zwakke zuurt itraties. In dit laatste geval is er ook een buffergebied en een half-equivalentiepunt, waarbij de pH gelijk is aan de pKa van het zuur. De concentraties van het zwakke zuur en zijn geconjugeerde base zijn gelijk. Aan de andere kant resulteert het titreren van sterke of zwakke basen met sterk zuur in een omgekeerde S-vormige curve, beginnend bij een hogere pH en afnemend met de toevoeging van het sterke zuur.

Zuur-base-titratiecurven

Acid-base titration can be performed to determine an unknown concentration of acid using a known concentration of a base or vice versa.&#160;
When ...

Education

JoVE Core

Analytical Chemistry

Analytische chemie

Unit 1

Acid–Base Titration

Zuur-base titratie

KEY TERMS AND CONCEPTS

BELANGRIJKE TERMEN EN CONCEPTEN

titration curves and ph changes

Acid-base titration uses a known acid or base to find the concentration of an unknown solution. A base can titrate an acid, or an acid can titrate a base. As titrant is added little by little, the pH changes in a predictable way.

The pH change is shown on a titration curve. A titration curve plots how the pH of the solution changes as more titrant is added. Scientists use this curve to follow the progress of the titration and to identify the endpoint, which is the point used to stop the process.

Titration curves can show several acid-base pairs. They may compare strong acid with strong base, strong acid with weak base, or weak acid with strong base. These curves usually have an S-shape, but the exact shape depends on whether the acid or base is strong or weak.

For a strong acid titrated with a strong base, the equivalence point is reached at pH 7. The equivalence point is where the moles of acid equal the moles of base, so the acid and base are completely neutralized. With a weak acid, the equivalence point is above pH 7 because the weak acid becomes its conjugate base.

The pH changes more sharply near the equivalence point in a strong acid titration than in a weak acid titration. Weak acid titrations also have a buffer region and a half-equivalence point. At the half-equivalence point, the pH equals the pKa of the acid, and the weak acid and its conjugate base have equal concentrations.

When a strong acid is used to titrate a strong base or a weak base, the curve is inverted. It starts at a higher pH and drops as more strong acid is added. This makes the titration curve a useful guide for tracking how the solution responds during the titration.

Titration Curves and pH Changes

acid&#8211;base titration: overview

Acid-base titration uses a known acid or base to find the concentration of an unknown solution. A base can titrate an acid, or an acid can titrate a base. As titrant is added little by little, the pH changes in a predictable way. The pH change is shown on a titration curve. A titration curve plots how the pH of the solution changes as more titrant is added. Scientists use this curve to follow the progress of the titration and to identify the endpoint, which is the point used to stop the...

titration of a strong acid with a strong base

titration-of-a-strong-acid-with-a-strong-base

pH Changes in Strong Acid-Base Titration

pH changes in a strong acid-strong base titration depend on the amount of leftover hydronium or hydroxide ions. A strong acid such as hydrochloric acid fully dissociates in water. That gives the solution hydronium ions and chloride ions, so the starting pH is low. When sodium hydroxide is added, it neutralizes hydronium ions. As more base is added, the concentration of hydronium ions falls and the pH rises. At the equivalence point, the hydronium ions have been neutralized and the solution is...

titration of a weak acid with a strong base

titration-of-a-weak-acid-with-a-strong-base

Weak Acid Titration Curve and pH Stages

Weak acid titration with a strong base changes pH in clear stages. The acid in this example is acetic acid, and the base is sodium hydroxide. Each stage uses a different pH calculation method. At the start, the pH of the weak acid is found with its dissociation constant, Ka, and an ICE table. An ICE table tracks the initial, change, and equilibrium amounts of the acid. This step describes the acid before much base is added. As sodium hydroxide is added, a buffer forms. A buffer is a solution...

titration of a weak base with a strong acid

titration-of-a-weak-base-with-a-strong-acid

Ammonia Titration Curve with HCl

Ammonia titration with hydrochloric acid shows how a weak base behaves as acid is added. The curve is the mirror image of a weak acid titrated with a strong base. In this case, ammonia acts as the weak base, and hydrochloric acid acts as the strong acid. The starting pH of 50 mL of 0.1 M ammonia is found with an ICE table and the Kb value. That calculation gives an initial pH of 11.11. As hydrochloric acid is added, the pH begins to fall. After 25 mL of 0.1 M hydrochloric acid is added, the...

titration of a weak acid with a weak base

titration-of-a-weak-acid-with-a-weak-base

Finding the Endpoint in Weak Acid–Base Titration

Weak acid and weak base titration is used to follow how pH changes as base is added. In this kind of titration, both the acid and the base dissociate only partly. The titration curve shows a slow, gradual pH change instead of a sharp jump. A common example is the titration of acetic acid with ammonia. During the reaction, these two species form ammonium acetate and water. Because the pH changes so gradually, there is no simple indicator that shifts color sharply at the equivalence point. One...

solution composition during acid/base titrations

solution-composition-during-acidbase-titrations

Acetic Acid Buffer Changes in Titration

Acetic acid buffer changes during a weak acid–strong base titration. When acetic acid is titrated with sodium hydroxide, the reaction forms water and the conjugate base of the acid, sodium acetate. The mixture of acetic acid and sodium acetate acts as a buffer, which helps show how solution makeup shifts during the titration. The relative amounts of acetic acid and acetate ions are tracked with α values. Here, α0 represents the equilibrium concentration of acetic acid, and α1 represents the...

mixtures of acids

Finding pH in Acid Mixtures

Finding pH in acid mixtures depends on the acids present and their dissociation constants. When a solution contains two acids, the pH can be found by choosing the method that matches their relative strengths. The key idea is that the stronger acid often controls the hydronium ion level, which is the amount of H3O+ in solution. In a mixture of a strong acid and a weak acid, the strong acid dissociates completely. It becomes the main source of hydronium ions in the solution. The weak acid...

titration in nonaqueous solvents

Nonaqueous Solvents for Sharper Titration Endpoints

Nonaqueous solvents can make acid-base titrations easier to read by giving sharper endpoints. Most acid-base titrations are done in water, but water can compete with weak acids or bases for proton donation or acceptance. That competition can blur the titration curve and make the endpoint less clear. Water also changes the partial ionization of weak acids and bases. For example, water can accept a proton from acetic acid to form hydronium and acetate ions. The hydronium ion is a stronger acid...

titration of polyprotic base with a strong acid

titration-of-polyprotic-base-with-a-strong-acid

Carbonate Buffering in Acid Titration

The titration of sodium carbonate with hydrochloric acid shows how a polyprotic base reacts in stages. A polyprotic base can accept more than one proton, so its titration curve has two equivalence points. These points mark where one form has been fully changed into the next. At the first equivalence point, carbonate ions are completely converted to bicarbonate ions. The region before this point is the carbonate/bicarbonate buffer. In this buffer region, both forms are present in the solution. <br...

titration of polyprotic acids with a strong base

titration-of-polyprotic-acids-with-a-strong-base

Polyprotic Acid Titration Curve Features

Polyprotic acid titration curves show how acids with more than one ionizable proton react with a strong base. Each proton is released in a separate step. Each step has its own dissociation constant, or Ka, and each later Ka is weaker than the one before it. When a polyprotic acid such as sulfurous acid is titrated with sodium hydroxide, the base first neutralizes the first ionizable proton. This forms an intermediate species, such as hydrogen sulfite ions. The first part of the curve looks...

composition of polyprotic acid solutions as a function of ph

composition-of-polyprotic-acid-solutions-as-a-function-of-ph

Polyprotic Acid Titration Fractions at Each pH

Polyprotic acid titration shows how the main species in solution change as pH changes. In a compound of the form H2M, there are two ionizable protons. That means the titration with a base produces two equivalence points on the curve. As base is added, three species can be present in the solution: H2M, HM−, and M2−. Their amounts are shown as fractions called α0, α1, and α2. These alpha values track how much of each form is present at different stages of the titration. At the start of the...

buffers: overview

Buffers and pH Stability

Buffers help keep the pH of a solution stable when small amounts of acid or base are added. They are made from a weak acid and its conjugate base, or from a weak base and its conjugate acid. This balance lets the solution resist large pH changes until the buffer capacity is exceeded. One common buffer uses acetic acid and sodium acetate. Here, CH3COOH acts as the weak acid and CH3COONa provides its salt. Another buffer uses ammonia and ammonium chloride, written as NH3 and NH4Cl. These...

buffers: buffer capacity

Buffer Capacity and pH Resistance

Buffer capacity describes how well a buffer resists changes in pH. It is a quantitative measure, so it tells how much acid or base a one-liter buffer solution can take before its pH shifts by 1 unit. In the equation, beta is the buffer capacity, while Ca and Cb represent the moles of acid and base added. The term dpH means the change in pH. A graph of pH versus the moles of base added to a weak acid with a pKa of 5 shows how buffering works as more base is added. Taking the derivative of that...

leveling effect

How Solvents Limit Acid and Base Strength

The leveling effect explains how a solvent can limit acid and base strength in solution. In acid-base chemistry, the solvent sets a ceiling on how strong an acid or base can act. Stronger acids or bases may react with the solvent itself instead of with the intended compound. When a base is stronger than the conjugate base of the solvent, it deprotonates the solvent first. A conjugate base is the species left after an acid loses a proton. This reaction keeps going until the stronger base is...

key terms and concepts

Learn how acid-base titration curves track pH changes, show equivalence points, and reveal strong and weak acid-base behavior in high school chemistry.

Titration Curves and pH Changes | JoVE K12

analytical chemistry

JoVE Core Analytical Chemistry simplifies complex chemical principles by breaking them down into clear, engaging animations, making topics from SI Units to NMR spectroscopy more accessible and straightforward. Additionally, the scientist-in-action videos highlight the application of these concepts in real-world research conducted in laboratories globally.

Alabama Course of Study Science

Matter and Its Interactions

9-12.C.1.6.e

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New York State Science Learning Standards

High School

Physical Science

HS. Chemical Reactions

HS-PS1-11.

Scientific Laws and Theories

Scientific Laws

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Elements: Chemical Symbols and Isotopes

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Use models to explain how the scientific understanding of atomic structure has evolved.

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Alpha (&#945;) decay is the ...

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Nuclear Binding Energy

The difference between the calculated and experimentally measured masses is known as the mass defect of the atom. In the case of helium-4, the mass defect ...

Radioactive Decay and Radiometric Dating

Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. ...

Nuclear Fission

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Nuclear Transmutation

Nuclear transmutation is the conversion of one nuclide into another. It can occur by the radioactive decay of a nucleus, or the reaction of a nucleus with ...

Use models to compare nuclear reactions including alpha decay, beta decay and gamma decay; nuclear fusion and nuclear fission.

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The Pauli Exclusion Principle

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The Energies of Atomic Orbitals

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The Aufbau Principle and Hund's Rule

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Use models to explain how electrons are distributed in atoms.

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Periodic Classification of the Elements

The periodic table arranges atoms based on increasing atomic number so that elements with the same chemical properties recur periodically. When their ...

The Periodic Table

As early chemists discovered more elements, they realized that various elements could be grouped by their similar chemical behaviors. One such grouping ...

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The elements in groups of the periodic table exhibit similar chemical behavior. This similarity occurs because the members of a group have the same number ...

Ionic Radii

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Ionization Energy

The amount of energy required to remove the most loosely bound electron from a gaseous atom in its ground state is called its first ionization energy ...

Electron Affinity

The electron affinity (EA) is the energy change for adding an electron to a gaseous atom to form an anion (negative ion).



This process can be either ...

Construct an explanation to infer the atomic size, reactivity, electronegativity, and ionization energy of an element based on its position in the Periodic Table.

PS.Chm.2.2

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The Born-Haber Cycle

Lattice Energy&#xA0;

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Trends in Lattice Energy: Ion Size and Charge

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Resonance

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Formal Charges

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Exceptions to the Octet Rule

Many covalent molecules have central atoms that do not have eight electrons in their Lewis structures. These molecules fall into three categories:


	...

Bond Energies and Bond Lengths

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Analyze and interpret data to explain the mechanisms and properties of the two main types of intramolecular (ionic and covalent) bonds.

PS.Chm.3.1

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Molecular Comparison of Gases, Liquids, and Solids

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Construct an explanation to summarize the influences intermolecular forces have on the properties of chemical compounds.

PS.Chm.3.2

Analyze the structure of atoms and isotopes.

Titration Curves and pH Changes

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