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

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Strong Acid and Base Solutions

Sterke zuren dissociëren volledig in water. Salpeterzuur valt bijvoorbeeld volledig uiteen in hydronium-ionen en nitraationen. Omdat de hydronium-ionen die worden gegenereerd door de autoprotolyse van water verwaarloosbaar zijn, is de concentratie van de hydronium-ionen in water gelijk aan de concentratie van het sterke zuur.De pH van deze oplossingen kan worden bepaald met behulp van de beginconcentratie van het sterke zuur. In een 0, 10 molaire HCl-oplossing zal HCl bijvoorbeeld volledig dissociëren in de hydronium-ionen en chloride-ionen, en daarom zal de hydronium-ionenconcentratie van de oplossing ook 0, 10 molair zijn. Door de negatieve logaritme van deze concentratie te nemen, is de pH van de oplossing gelijk aan één.Omgekeerd kan de pH van een oplossing worden gebruikt om de hydronium-ionenconcentratie van een oplossing te bepalen. Voor een oplossing met pH 3, 60 kan de hydronium-ionenconcentratie bijvoorbeeld worden bepaald door de vergelijking op te lossen, 3, 60 is gelijk aan de negatieve log van de hydronium-ionenconcentratie. Om de concentratie op te lossen, vermenigvuldigt u beide zijden met een negatieve en neemt u vervolgens de antilog van beide zijden.De concentratie aan hydronium-ionen is gelijk aan 2, 5 10⁻⁴ molair. Sterke basen die metaalhydroxiden uit groep één zijn, zoals natriumhydroxide en kaliumhydroxide, dissociëren volledig in oplossing. Bijvoorbeeld, 0, 20 molair natriumhydroxide zal volledig dissociëren in water en 0, 20 molair natriumionen en 0, 20 molair hydroxide-ionen produceren.Groep twee metaalhydroxiden echter, zoals bariumhydroxide en calciumhydroxide, produceren twee mol hydroxide-ionen voor elke mol base. Bijvoorbeeld, 0, 020 molair calciumhydroxide zal volledig dissociëren in water en zal 0, 020 molair calciumionen en 0, 040 molair hydroxide-ionen produceren. Ionische metaaloxiden, zoals natriumoxide en calciumoxide, zijn ook sterke basen.Hun oxide-ion reageert met water en produceert hydroxide-ionen. De concentratie van hydroxide-ionen kan worden gebruikt om een pOH en pH van de oplossing te berekenen. Een kaliumhydroxideoplossing van 5 10⁻⁵ molair heeft bijvoorbeeld evenveel hydroxide-ionen als sterke base en heeft daarom een pOH van 4, 30.Net als pH kan een pOH van de oplossing ook worden gebruikt om de hydroxide-ionenconcentratie te bepalen door de volgende vergelijking op te lossen:pOH is gelijk aan de negatieve log van de hydroxide-ionenconcentratie. Omdat pH plus pOH gelijk is aan 14 en de pOH 4, 3 is, is de pH van de oplossing 9, 7.

sterke zuur- en baseoplossingen

Een sterk zuur is een verbinding die volledig dissocieert in een waterige oplossing en een concentratie hydroniumionen produceert die gelijk is aan de initiële zuurconcentratie. 0,20 M broomwaterstofzuur zal bijvoorbeeld volledig dissociëren in water en produceert 0,20 M hydroniumionen en 0,20 M bromide-ionen. <img alt="Eq1" src="/files/ftp_upload/11399/11399_Equation_1.png" style="height: 50px;"> Aan de andere kant is een sterke base een verbinding die volledig dissocieert in een waterige oplossing en hydroxide-ionen produceert. 0,015 M KOH, een metaalhydroxide uit groep 1, zal bijvoorbeeld volledig dissociëren en 0,015 M OH- en 0,015 M K+ produceren. <img alt="Eq2" src="/files/ftp_upload/11399/11399_Equation_2.png" style="height: 50px;"> Metaalhydroxiden uit Groep 2, zoals bariumhydroxide [Ba(OH)2] en strontiumhydroxide [Sr(OH)2], zijn ook sterke basen en bezitten twee hydroxide-ionen. Hierdoor produceren ze een meer basische oplossing vergeleken met NaOH of KOH bij dezelfde concentratie. 0,015 M Ba(OH)2  produceert 0,015 M Ba+  en 0,030 M hydroxide. <img alt="Eq3" src="/files/ftp_upload/11399/11399_Equation_3.png" style="height: 50px;"> Omdat sterke zuren en basen volledig dissociëren, kunnen molaire verhoudingen worden gebruikt om hun hydronium- en hydroxideconcentraties te bepalen, die op hun beurt kunnen worden gebruikt om de pH of pOH van een oplossing te berekenen. Een HCl-oplossing van 0,030 M produceert bijvoorbeeld 0,03 M hydroniumionen. Daarom zal de pH van deze oplossing zijn <img alt="Eq4" src="/files/ftp_upload/11399/11399_Equation_4.png" style="height: 135px;"> De pOH van dezelfde oplossing kan worden bepaald met behulp van de formule <img alt="Eq5" src="/files/ftp_upload/11399/11399_Equation_5.png" style="height: 50px;"> Omdat de pH van de oplossing 1,52 is, kan de pOH ervan worden berekend als <img alt="Eq6" src="/files/ftp_upload/11399/11399_Equation_6.png" style="height: 50px;"> Op dezelfde manier kan de concentratie van hydroxide-ionen geproduceerd door sterke basen worden gebruikt om de pOH van een oplossing te bepalen met behulp van de vergelijking <img alt="Eq7" src="/files/ftp_upload/11399/11399_Equation_7.png" style="height: 50px;"> De bovenstaande vergelijking kan ook worden gebruikt om de hydroxide-ionconcentratie te bepalen wanneer pOH bekend is. Als de pOH van een oplossing bijvoorbeeld 3,00 is, <img alt="Eq8" src="/files/ftp_upload/11399/11399_Equation_8.png" style="height: 50px;"> Vermenigvuldiging van beide zijden met −1 geeft <img alt="Eq9" src="/files/ftp_upload/11399/11399_Equation_9.png" style="height: 50px;"> Neem nu de antiloog van beide kanten <img alt="Eq10" src="/files/ftp_upload/11399/11399_Equation_10.png" style="height: 90px;"> De hydroniumionenconcentratie van de oplossing met pOH 3 is dus 1,0 × 10−3 M. Een soortgelijke methode kan worden gebruikt om de hydroniumionenconcentratie van een oplossing te bepalen als de pH ervan bekend is.

Sterke zuur- en baseoplossingen

A strong acid is a compound that dissociates completely in an aqueous solution and produces a concentration of hydronium ions equal to the initial ...

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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

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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

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Strong Acids, Strong Bases, and pH

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