Knowt0.0(0)
Holt Chemistry Chapter 15: Acids and Bases
Holt Chemistry Chapter 15: Acids and Bases
15.1 What Are Acids and Bases?
- Acids are electrolytes and can conduct electric currents
- Acids react with metals. They usually produce hydrogen gas
- Strong acids will ionize completely in a solution
- This is a completion reaction
- Strong acids are better conductors of electricity
- HCl is a strong acid
- HBr is a strong acid
- HI is a strong acid
- HNO3 is a strong acid
- H2SO4 is a strong acid
- HClO4 is a strong acid
- HIO4 is a strong acid
- Weak acids will release few hydrogen ions in aqueous solutions
- They have smaller a Keq than the strong acids
- CH3COOH is a weak acid
- HCN is a weak acid
- HF is a weak acid
- HNO2 is a weak acid
- H2SO3 is a weak acid
- HOCl is a weak acid
- H3PO4 is a weak acid
- The Arrhenius definition of an acid is limited to aqueous solutions
- Arrhenius states that an acid is any substance that, when added to water, increases the hydronium ion concentration
- Acids are usually gases or liquids
- The hydronium ion is H3O+
- Bases are also electrolytes
- Bases are usually solids
- Bases feel slippery because they react with the oil in your hands, converting the bases into soaps
- Some bases are insoluble while others are soluble
- Very soluble bases are called alkalis
- Strong bases ionize completely in a solvent
- NaOH is a strong base
- KOH is a strong base
- Ca(OH)2 is a strong base
- Ba(OH)2 is a strong base
- Na3PO4 is a strong base
- Weak bases release few hydroxide ions in aqueous solutions
- NH3 is a weak base
- Na2CO3 is a weak base
- K2CO3 is a weak base
- C6H5NH2 is a weak base
- (CH3)3N is a weak base
- The hydroxide ion is OH-
- The Arrhenius definition of a base is a substance, when dissolved in water, increases the hydroxide ion concentration
- The Arrhenius definitions are limited to aqueous solutions
- The Arrhenius definitions cannot classify substances that sometimes act as bases and sometimes act as acids
- The Bronsted-Lowry definition of an acid is any substance that can donate a proton
- The Bronsted-Lowry definition of a base is any substance that can accept a proton
- The Bronsted-Lowry proton is most commonly referred to as H+
- The Bronsted-Lowry definitions are not limited to aqueous solutions
- A conjugate acid in an acid that forms when a base gains a proton
- A conjugate acid is a base that forms when an acid loses a proton
- Conjugate acids pair up with bases
- Conjugate bases pair up with acids
- Acids and bases are always reactants
- Conjugate acids and conjugate bases are always products
- Amphoteric describes a substance, such as water, that has properties of both acids and bases
15.2 Acidity, Basicity, and pH
- When a water molecule donates a proton to another water molecule, both a hydronium ion and hydroxide ion form. This is known as the self-ionization of water
- The self-ionization of water is a special equilibrium constant
- It is represented with the symbol Kw
- The equation to find the self-ionization of water is Kw = [H3O+] x [OH-]
- The concentrations of hydronium [H3O+] are equal to the concentrations of hydroxide [OH-]
- [H3O+] = [OH-] = 1.00 x 10-7
- Kw = 1.00 x 10-14
- Using this formula, you can calculate an unknown concentration
- The concentration of hydronium ions is expressed as acidity
- The concentration of hydroxide ions is expressed as basicity
- If the concentrations are equal then the solution is neutral
- pH stands for the power of hydronium
- The pH is on a negative logarithmic scale, meaning a lower pH has a higher hydronium concentration
- pOH stands for power of hydroxide
- A pH of 7 is neutral
- Below are different equations to solve for pH, pOH, and concentrations
- pH = -log[H3O+]
- [H3O+] = 10-pH
- pOH = -log[OH-]
- [OH-] = 10-pOH
- pH + pOH = 14
- Indicators change color, the color will then tell you what pH the substance is
- pH meters can also be used
15.3 Neutralization and Titrations
- A neutralization reaction is when and acid and a base form water and a salt
- This reaction will form equal concentrations of hydronium and hydroxide
- When the neutralization reaction is complete, this is known as the equivalence point
- This is when the concentrations are equal
- This is different than the endpoint
- The endpoint is when a color change occurs
- However, if a correct indicator is used, the endpoint can be the same as the equivalence point
- Titration is the method used to determine the concentration of an unknown substance. It is done by adding concentration of a known solution until a color change occurs in the mixture
- The solution added is called the titrant
- The equipment used in a titration are two burets, a titration flask, and an indicator
- The solution of a known concentration is called a standard solution
- Titration curves show pH plotted against volume
- The curve will be steep at the equivalence point
- Indicators have transition range. They do not cover the whole pH scale, but rather small sections
- Thymol blue ranges from 1.2-2.8
- Methyl orange ranges from 3.1-4.4
- Litmus ranges from 5.0-8.0
- Bromthymol blue ranges from 6.0-7.6
- Phenolphthalein ranges from 8.0-9.6
- Alizarin yellow ranges from 10.1-12.0
- n = cV
- n is the amount of solute in moles
- c is the concentration in moles per liter
- V is the volume in liters
- (c H3O+)(V H3O+) = (c OH-)(V OH-)
- Therefore cV = cV
15.4 Equilibria of Weak Acids and Bases
- Some acids are able to donate protons better, therefore they are stronger acids
- Some bases accept protons better, therefore they are stronger bases
- The general principle states In an acid-base reaction, the conjugate base of the stronger acid is the weaker base, and the conjugate acid of the stronger base is the weaker acid
- The acid-ionization constant describes the ionization of acid in water
- Ka
- The formula can be expressed has [H3O+][other product] / [reactant] = Ka
- A buffer solution is made from a weak acid and its conjugate base
- Buffers neutralize small amounts of acids or bases
- Buffers can be found in blood, foods, milk, and more
0.0(0)
