Name: strong acids, strong bases, and ph
Uploaded: 2020-09-24T15:06:51.000Z
Duration: 3 min 22 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Chemistry

Matter and its Interactions

PS.Chm.6.3

Strong Acid and Base Solutions

强酸在溶液中完全分解。例如，硝酸完全分解 成水合氢离子和硝酸根离子。由于水自电离产生的水合氢离子 可以忽略不计，因此 水中水合氢离子的浓度 等于强酸的浓度。这些溶液的 pH 值可以 用强酸的初始浓度来确定。例如，在 0.10 M 的 HCl 溶液中，HCl 将完全分解成水合氢离子 和氯离子，因此溶液中的水合氢离子 浓度也将为 0.10 M。取这个浓度的负对数，溶液的 pH 值等于 1。反过来，溶液的 pH 值可 用于测定溶液中的 水合氢离子浓度。例如，对于 pH 值为 3.60 的溶液，其水合氢离子浓度可通过求解 该方程式来确定，3.60=水合氢离子 浓度的负对数。为了求解该浓度，两边同时乘以 负一，然后取两边的反对数。水合氢离子浓度等于 2.5 10⁻⁴ M.属于第一组金属氢氧化物的强碱，如 氢氧化钠和氢氧化钾，完全分解成溶液。例如，0.20 M 氢氧化钠在水中 会完全解离，将会产生 0.20M 钠离子 和 0.20M 氢氧化物离子。然而，第二组金属氢氧化物，如氢氧化钡和氢氧化钙，每摩尔碱产生两摩尔氢氧化物离子。例如，0.020M 氢氧化钙将在水中 完全离解，并将产生 0.020M 钙离子 和 0.040M 氢氧化物离子。离子型金属氧化物，如氧化钠和氧化钙，也是强碱。它们的氧化物离子与水反应，产生氢氧化物离子。氢氧化物离子的浓度 可用于计算溶液的 pOH 和 pH 值。例如，5×10⁻⁵M 氢氧化钾溶液具有等量的 氢氧化物离子作为强碱，因此 pOH 为 4.30。与 pH 一样，溶液的 pOH 也可 用于通过求解以下方程来确定氢氧化物 离子浓度：pOH 等于氢氧化物 离子浓度的负对数。由于 pH 加 pOH 等于 14，而 pOH 为 4.3，因此溶液的 pH 值为 9.7。

强酸和碱溶液

强酸是一种在水溶液中完全分离的化合物，产生的浓度为水合氢离子，等于酸的初始浓度。 例如， 0.20 M 氢溴酸将在水中完全分离，产生 0.20 M 水合氢离子和 0.20 M 溴离子。 
 <img alt="Eq1" src="/files/ftp_upload/11399/11399_Equation_1.png" style="height: 50px;" />
 另一方面，强碱是一种在水溶液中完全分离并产生氢氧化物离子的化合物。 例如， 0.015 M KOH (1 类金属氢氧化物) 将完全分离，产生 0.015 M OH- 和 0.015 M K+。 
 <img alt="Eq2" src="/files/ftp_upload/11399/11399_Equation_2.png" style="height: 50px;" />
 第 2 类金属氢氧化物，如钡氢氧化物 [Ba(OH)2] 和锶氢氧化物 [Sr(OH)2]，也是强碱，并拥有两个氢氧化物离子。 这就导致他们在同一个浓度生产比 NaOH 或 KOH 更基本的溶液。 例如， 0.015 M Ba(OH)2  产生 0.015 M Ba+  和 0.030 M 氢氧化物。 
 <img alt="Eq3" src="/files/ftp_upload/11399/11399_Equation_3.png" style="height: 50px;" />
 由于强酸和碱完全分离，摩尔比可用于确定其水合氢离子和氢氧化物浓度，而后者可用于计算溶液的 pH 或 pOH。 例如， 0.030 M HCl 溶液将产生 0.03 M 水合氢离子。 因此，该溶液的 pH 值将为 
 <img alt="Eq4" src="/files/ftp_upload/11399/11399_Equation_4.png" style="height: 135px;" />
 可以使用确定同一溶液的 pOH 公式 
 <img alt="Eq5" src="/files/ftp_upload/11399/11399_Equation_5.png" style="height: 50px;" />
 由于溶液的 pH 值为 1.52 ，其 pOH 可以计算为 
 <img alt="Eq6" src="/files/ftp_upload/11399/11399_Equation_6.png" style="height: 50px;" />
 同样，强碱产生的氢氧化物离子的浓度可用于使用方程测定溶液的 pOH 
 <img alt="Eq7" src="/files/ftp_upload/11399/11399_Equation_7.png" style="height: 50px;" />
 当已知 pOH 时，上述方程也可用于确定氢氧化物离子浓度。 例如，如果溶液的 pOH 为 3.00 ， 
 <img alt="Eq8" src="/files/ftp_upload/11399/11399_Equation_8.png" style="height: 50px;" />
 两侧乘以 −1 给出 
 <img alt="Eq9" src="/files/ftp_upload/11399/11399_Equation_9.png" style="height: 50px;" />
 现在，两侧都提反对数 
 <img alt="Eq10" src="/files/ftp_upload/11399/11399_Equation_10.png" style="height: 90px;" />
 因此，带有 pOH 3 的溶液的水合氢离子浓度为 1.0 × 10−3 M。 如果已知溶液的 pH 值，可以使用类似方法来确定其水合氢离子浓度。

强酸是一种在水溶液中完全解离的化合物，产生的水合氢离子浓度等于其初始浓度……

Education

教育

JoVE Core

化学

Acids and Bases

酸与碱

KEY TERMS AND CONCEPTS

关键术语与概念

strong acids, strong bases, and ph

Strong acids and strong bases change the pH of a solution by dissociating completely in water. A strong acid produces hydronium ions, which are H3O+ ions, and a strong base produces hydroxide ions, OH-. Because the dissociation is complete, the ion concentration can be found from the starting concentration and the molar ratio.

For example, 0.20 M hydrobromic acid dissociates fully in water. It produces 0.20 M hydronium ions and 0.20 M bromide ions. A 0.015 M KOH solution also dissociates completely. It produces 0.015 M OH- and 0.015 M K+.

Some group 2 metal hydroxides are also strong bases. Barium hydroxide, Ba(OH)2, and strontium hydroxide, Sr(OH)2, each contain two hydroxide ions. That means they create a more basic solution than NaOH or KOH at the same concentration. For example, 0.015 M Ba(OH)2 produces 0.015 M Ba+ and 0.030 M hydroxide.

The ion concentrations from strong acids and strong bases can be used to calculate pH and pOH. A 0.030 M HCl solution produces 0.03 M hydronium ions, so its pH can be found from that concentration. The same pH value can then be used to determine pOH. If the pH is 1.52, the pOH can be calculated from the relationship between them.

The same idea works for strong bases. The hydroxide ion concentration can be used to find pOH with the equation for pOH, and the equation can also be used in reverse when pOH is known. For example, if the pOH of a solution is 3.00, multiplying by -1 and taking the antilog gives a hydronium ion concentration of 1.0 × 10^-3 M. The same method can be used to find hydronium ion concentration when pH is known.

Strong Acids, Strong Bases, and pH

bronsted-lowry acids and bases

Proton Transfer in Acids and Bases

Acids and bases can be understood through proton transfer. Early scientists described acids by their sour taste, their effect on dyes, and their reaction with limestone, which releases carbon dioxide. Robert Boyle also noted that acid solutions can lose these properties after contact with alkali, or base, solutions. The modern view developed step by step. Humphry Davy showed that hydrogen is the essential part of acids. Joseph Louis Gay-Lussac then described acids as substances that neutralize...

water: a bronsted-lowry acid and base

Water as an Amphiprotic Substance

Water can act as both a Brønsted-Lowry acid and a Brønsted-Lowry base. When hydrogen fluoride dissolves in water, it donates protons to water. This is acid ionization. The products are hydronium ions and fluoride ions. Water can also accept protons from another substance. When pyridine dissolves in water, it accepts a proton from water molecules. This is base ionization. The products are hydroxide ions and pyridinium ions. These reactions show that water can play either role. A substance that...

ph scale

pH and pOH in Water

pH and pOH show how hydronium and hydroxide ions behave in water and other aqueous solutions. These ion concentrations are linked by the ion product of water, K w , so when one goes up, the other goes down. Because ion concentrations can differ by huge amounts, a logarithmic scale is used to describe them. pH is defined from the hydronium ion concentration, [H3O+], and pOH is the matching p-function for hydroxide ion concentration. These two values are also connected through the K w...

relative strengths of conjugate acid-base pairs

relative-strengths-of-conjugate-acid-base-pairs

How Ka and Kb Show Acid-Base Strength

Brønsted-Lowry acid-base chemistry is based on proton transfer. That idea helps show how the strength of an acid is linked to the strength of its conjugate base, and vice versa. Acid and base strength is measured with ionization constants, Ka and Kb, which tell how far an ionization reaction goes. For the conjugate pair HA and A−, the acid ionizes in water and the base reaction can be written for the partner species. When the two reactions are added, they give the autoionization of water. The...

strong acid and base solutions

Strong acids and strong bases change the pH of a solution by dissociating completely in water. A strong acid produces hydronium ions, which are H3O+ ions, and a strong base produces hydroxide ions, OH-. Because the dissociation is complete, the ion concentration can be found from the starting concentration and the molar ratio. For example, 0.20 M hydrobromic acid dissociates fully in water. It produces 0.20 M hydronium ions and 0.20 M bromide ions. A 0.015 M KOH solution also dissociates...

weak acid solutions

Weak Acid Equilibrium in Water

Weak acid equilibrium in water explains why many acids only partially react when dissolved. Most weak acid molecules stay in their original form, and only a small amount of hydronium ions forms. Weak acids are common in nature. They help create the tangy taste of citrus fruits, the stinging sensation from insect bites, and the smells linked to body odor. Acetic acid is a familiar weak acid. It is the main ingredient in vinegar. Its equation uses a double arrow to show that the reaction with...

weak base solutions

Weak Base pH and Kb Calculations

Weak base pH and Kb calculations show how partially reacting bases change water chemistry. Weak bases produce hydroxide ions when they dissolve by reacting with water molecules. Because the reaction only happens partly, these compounds are classified as weak bases. Weak bases are common in nature and in technology. Ammonia is one major example. Global production of ammonia is typically well over 100 metric tons each year. It is used as an agricultural fertilizer, a starting material for...

mixtures of acids

pH of Acid Mixtures

The pH of acid mixtures depends on the acids present, their dissociation constants, and their starting concentrations. When a solution contains two different acids, the pH can be found by choosing the method that fits their relative strengths. This makes acid mixtures a useful case for applying acid-base rules in chemistry. In a mixture of a strong acid and a weak acid, the strong acid dissociates completely and supplies almost all of the hydronium ions in the solution. The weak acid...

ions as acids and bases

Salt Hydrolysis and pH of Solutions

Salt hydrolysis explains why some salt solutions are acidic, basic, or neutral. Salts are ionic compounds made of cations and anions. In water, either ion may react with water through an acid or base ionization reaction. The pH of the solution depends on the relative acid-base strength of the ions in the salt. Ammonium chloride is a good example of an acidic salt. When it dissolves, it separates into ammonium ions and chloride ions. The ammonium ion is the conjugate acid of ammonia, so it can...

determining the ph of salt solutions

Salt Hydrolysis and pH in Solutions

Salt hydrolysis and pH in solutions depend on the ions released when a salt dissolves. Some ions react with water, while others do not. The balance between the cation and anion helps show whether the solution becomes acidic, basic, or neutral. Salts with pH-neutral anions and cations that produce hydronium ions give acidic solutions with pH below 7. Ammonium nitrate is one example. In NH4NO3, NO3− does not react with water, but NH4+ forms hydronium ions, so the solution is acidic. Other salts...

acid/base strengths and dissociation constants

acidbase-strengths-and-dissociation-constants

Acid and Base Strength in Water

Acid and base strength in water depends on how much a substance ionizes after it dissolves. If ionization is nearly complete, the substance is called strong. If only a small amount ionizes, it is called weak. Weak acids and weak bases are much more common than strong ones. The most common strong acids are HClO4, HCl, HBr, HI, HNO3, and H2SO4. The most common strong bases are LiOH, NaOH, KOH, Ca(OH)2, Sr(OH)2, and Ba(OH)2. These strong acids and bases ionize essentially completely in water. <br...

polyprotic acids

Stepwise Ionization of Polyprotic Acids

Polyprotic acids lose hydrogen ions in steps. The number of ionizable protons in a molecule determines whether an acid is monoprotic, diprotic, or triprotic. This video also shows that polyprotic bases can accept more than one proton. Monoprotic acids have one ionizable hydrogen atom per molecule. Examples include HCl, HNO3, and HCN. Their reactions with water form hydronium ions and the matching anion. Acetic acid, CH3CO2H, is also monoprotic because only the hydrogen in the carboxyl group...

acid strength and molecular structure

How Bonding Affects Acid Strength

Acid strength depends on bonding, electronegativity, and oxidation number. These factors help explain why some hydrogen compounds act as strong acids, while others behave as weak acids or bases. For binary acids, which are hydrogen compounds with one other nonmetal, acidity increases as the H-A bond gets weaker down a group. That is why the order for group 17 is HF &lt; HCl &lt; HBr &lt; HI, and for group 16 it is H2O &lt; H2S &lt; H2Se &lt; H2Te. Across a period, acid strength increases as...

lewis acids and bases

Electron-Pair Reactions in Acid-Base Chemistry

Electron-pair reactions explain Lewis acid-base chemistry. In 1923, G. N. Lewis described acids and bases by how they accept or donate a pair of electrons. When that electron pair forms a coordinate covalent bond, one atom supplies both bonding electrons. This bond is also called a dative bond. A simple example is the reaction of water with a hydrogen ion to make a hydronium ion. Ammonia can also combine with a hydrogen ion to form an ammonium ion. In both cases, the reaction creates a Lewis...

key terms and concepts

Learn how strong acids and strong bases dissociate completely in water and how their ion concentrations are used to calculate pH and pOH.

Strong Acids, Strong Bases, and pH | JoVE K12

chemistry

JoVE Core 化学通过简单明了且通俗易懂的动画视频课程，将普通化学概念带入到现实生活当中。此外，在科学家行动视频中，我们演示了在实验室中进行的经典和原始研究实验。

Physical Science

PS.PSc.2.5

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Interactions Of Matter

Chemical reactions

Minnesota Academic Standards in Science

1.2.1 9L.4.2.2.1

Texas Essential Knowledge and Skills

High School

CHEM.12

CHEM.12.C

Alabama Course of Study Science

Matter and Its Interactions

9-12.C.1.6.a

9-12.PS.3.6.c

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Chemical Reactions

HS-PS1-11.

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Strong Acids, Strong Bases, and pH

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