Acids have a sour taste. ---------- Acids cause some dyes to change color. ---------- Bases have a bitter taste. ---------- Bases have a slippery feel. ---------- All acids contain hydrogen. ---------- ;;; Some substances containing hydrogen are not acids. Some substances containing hydrogen are bases. ---------- Acids are substances. ---------- An Arrhenius acid produces H-plus ions in water. ---------- Bases are substances. ---------- An Arrhenius base produces OH-minus ions in water. ---------- The properties of aqueous solutions of Arrhenius acids are due to H-plus ions. ---------- The properties of aqueous solutions of Arrhenius bases are due to OH-minus ions. ---------- Any Arrhenius acid dissolved in water increases the concentration of H-plus ions in the water. ---------- Any Arrhenius base dissolved in water increases the concentration of OH-minus ions in the water. ---------- Hydrogen chloride is an Arrhenius acid. ---------- Hydrogen chloride gas is highly soluble in water. ---------- Hydrogen chloride gas in water reacts with the water. ---------- The reaction produces H-plus ions and Cl-minus ions. ---------- HCl is hydrogen chloride. ---------- Hydrochloric acid is an aqueous solution of HCl. ---------- 37 percent of the mass of concentrated hydrochloric acid is HCl. ---------- The concentration of HCl in concentrated hydrochloric acid is 12 M. ---------- Sodium hydroxide is an Arrhenius base. ---------- NaOH is sodium hydroxide. ---------- NaOH is an ionic compound. ---------- NaOH dissolves in water. ---------- NaOH dissociates in water. ---------- The dissociating produces Na-plus ions and OH-minus ions. ---------- Arrhenius acids and Arrhenius bases are defined only for aqueous solutions. ---------- ;;; Bronsted-Lowry acids are more general than Arrhenius acids. Arrhenius acids are Bronsted-Lowry acids. ---------- ;;; Bronsted-Lowry bases are more general than Arrhenius bases. Arrhenius bases are Bronsted-Lowry bases. ---------- ; [begin subsection: The H-plus Ion in Water] ;;; An H-plus ion is a proton with no valence electron. An H-plus ion is a proton with zero valence electrons. ---------- An H-plus ion is a small particle. ---------- An H-plus ion has a positive charge. ---------- ;;; An H-plus ion reacts strongly with the nonbonding electron pair of a water molecule. An H-plus ion reacts with the two nonbonding electrons of a water molecule. ---------- The reaction produces a hydronium ion. ---------- HO3-plus is a hydronium ion. ---------- ;;; An HO3-plus ion sometimes reacts with an H2O molecule. An HO3-plus ion reacts with an H2O molecule. ---------- The reaction produces an H5O2-plus ion. ---------- ;;; An HO3-plus ion sometimes reacts with three H2O molecules. An HO3-plus ion reacts with three H2O molecules. ---------- The reaction produces an H9O4-plus ion. ---------- ;;; An H-plus ion in water is quickly converted to an HO3-plus ion. An H-plus ion in water is converted to an HO3-plus ion. ---------- HCl dissolves in water. ---------- The HCl molecules react with the water molecules. ---------- The reaction transfers an H-plus ion from an HCl molecule to a water molecule. ---------- The reaction produces a hydronium ion and a chloride ion. ---------- Cl-minus is a chloride ion. ---------- Equation 16.3 is "HCl(g) + H_2O(l) --> H_3O^+(aq) + Cl^-(aq)". ---------- A Bronsted-Lowry acid is a substance. ---------- ;;; A molecule of a Bronsted-Lowry acid can donate a proton to another substance. A molecule of a Bronsted-Lowry acid donates a proton to a second substance. ---------- ;;; An ion of a Bronsted-Lowry acid can donate a proton to another substance. An ion of a Bronsted-Lowry acid donates a proton to a second substance. ---------- A Bronsted-Lowry base is a substance. ---------- ;;; A molecule of a Bronsted-Lowry base can accept a proton from another substance. A molecule of a Bronsted-Lowry base accepts a proton from a second substance. ---------- ;;; An ion of a Bronsted-Lowry acid can accept a proton from another substance. An ion of a Bronsted-Lowry acid accepts a proton from a second substance. ---------- An HCl molecule in water donates a proton to an H2O molecule. ---------- ;; The HCl molecule acts as a Bronsted-Lowry acid. The HCl molecule plays a Bronsted-Lowry acid. ---------- An H2O molecule accepts a proton from an HCl molecule in water. ---------- ;;; Bronsted-Lowry acids and Bronsted-Lowry bases can react without an aqueous solution. A Bronsted-Lowry acid and a Bronsted-Lowry base react without an aqueous solution. ---------- HCl reacts with NH3 without an aqueous solution. ---------- The reaction transfers a proton from an HCl molecule to an NH3 molecule. ---------- NH3 is a Bronsted-Lowry base. ---------- HCl gas reacts with NH3 gas. ---------- The reaction produces NH4Cl. ---------- The NH4Cl is mostly solid particles. ---------- The NH4Cl particles form a white fog. ---------- The white fog creates a hazy film on nearby windows. ---------- Equilibrium occurs in an aqueous solution of ammonia. ---------- NH3 is ammonia. ---------- ;;; Adding ammonia to water increases the concentration of OH-minus (aq). Adding ammonia to water increases the concentration of OH-minus. ---------- Ammonia is an Arrhenius base. ---------- Ammonia accepts a proton from H2O. ---------- Ammonia is a Bronsted-Lowry base. ---------- The H2O molecule in Equation 16.5 donates a proton to the NH3 molecule. ---------- ;;; The H2O molecule acts as a Bronsted-Lowry acid. The H2O molecule plays a Bronsted-Lowry acid. ---------- ;;; A Bronsted-Lowry acid always reacts with a nearby Bronsted-Lowry base. A Bronsted-Lowry acid reacts with a nearby Bronsted-Lowry base. ---------- The reaction transfers a proton from the acid to the base. ---------- IF a substance plays a Bronsted-Lowry base THEN a nearby substance plays a Bronsted-Lowry acid. ---------- A molecule of a Bronsted-Lowry acid must have a hydrogen atom. ---------- The hydrogen atom must detach from the molecule. ---------- The detaching must convert the hydrogen atom to an H-plus ion. ---------- An ion of a Bronsted-Lowry acid must have a hydrogen atom. ---------- The hydrogen atom must detach from the ion. ---------- The detaching must convert the hydrogen atom to an H-plus ion. ---------- A molecule of a Bronsted-Lowry base must have a nonbonding pair of electrons. ---------- The pair of electrons must bind to an H-plus ion. ---------- An ion of a Bronsted-Lowry base must have a nonbonding pair of electrons. ---------- The pair of electrons must bind to an H-plus ion. ---------- ;;; Some substances sometimes act as a Bronsted-Lowry acid and sometimes act as a Bronsted-Lowry base. Some substances play a Bronsted-Lowry acid. Some substances play a Bronsted-Lowry base. ---------- ;;; These substances are called amphoteric substances. These substances are amphoteric substances. ---------- H2O plays a Bronsted-Lowry base in a reaction with HCl. ---------- H2O plays a Bronsted-Lowry acid in a reaction with NH3. ---------- H2O is an amphoteric substance. ---------- An amphoteric substance combined with a more acidic substance plays a Bronsted-Lowry base. ---------- An amphoteric substance combined with a more basic substance plays a Bronsted-Lowry acid. ---------- ;;; In an acid-base equilibrium the reactions in both directions involve proton transfers. The reactions in both directions involve proton transfers in an acid-base equilibrium. ---------- Equation 16.6 is "HX(aq) + H_20(l) <--> X^-(aq) + H_3O^+(aq)". ---------- "HX" denotes an acid in Equation 16.6. ---------- "HX" donates a proton to the H2O molecule in the forward reaction of Equation 16.6. ---------- ;;; The "HX" molecule acts as a Bronsted-Lowry acid and the H2O molecule acts as a Bronsted-Lowry base. The "HX" plays a Bronsted-Lowry acid. The H2O molecule plays a Bronsted-Lowry base. ---------- The H3O-plus ion donates a proton to the X-minus ion in the reverse reaction of Equation 16.6. ---------- ;;; The H3O-plus ion acts as a Bronsted-Lowry acid and the X-minus ion acts as a Bronsted-Lowry base. The H3O-plus ion plays a Bronsted-Lowry acid. The X-minus ion plays a Bronsted-Lowry base. ---------- The "HX" in Equation 16.6 donates a proton. ---------- The donating leaves behind an X-minus ion. ---------- ;;; The X-minus ion acts as a Bronsted-Lowry base in the reverse reaction. The X-minus ion plays a Bronsted-Lowry base in the reverse reaction. ---------- The H2O molecule in Equation 16.6 accepts a proton. ---------- The accepting produces an H3O-plus ion. ---------- ;;; The H3O-plus ion acts as a Bronsted-Lowry acid in the reverse reaction. The H3O-plus ion plays a Bronsted-Lowry acid in the reverse reaction. ---------- ;;; An acid and a base differing only in a proton are called a conjugate acid-base-pair. ;;; [Too difficult to reformulate] ;;; Every acid has a conjugate base. Acid have conjugate bases. ---------- Removing a proton from the acid produces the conjugate base. ---------- OH-minus is the conjugate base of H2O. ---------- X-minus is the conjugate base of "HX". ---------- ;;; Every base has a conjugate acid. Bases have conjugate acids. ---------- Adding a proton to the base produces the conjugate acid. ---------- H3O-plus is the conjugate acid of H2O. ---------- "HX" is the conjugate acid of X-minus. ---------- ;;; Two sets of acid-base conjugate pairs are in every acid-base reaction. An acid-base reaction contains two sets of acid-base conjugate pairs. ---------- HNO2 is nitrous acid. ---------- Nitrous acid reacts with water in Equation 16.7. ---------- Equation 16.7 is "HNO_2(aq) + H_2O(l) <--> NO_2^-(aq) + H_3O^+(aq)". ---------- ;;; The HNO2 molecule in Equation 16.7 acts as a Bronsted-Lowry acid. The "HNO_2" in Equation 16.7 plays a Bronsted-Lowry acid. ---------- ;;; The H2O molecule in Equation 16.7 acts as a Bronsted-Lowry base. The H2O molecule in Equation 16.7 plays a Bronsted-Lowry base. ---------- ;;; NO2-minus ion in Equation 16.7 acts as the conjugate base for the HNO2 molecule. The NO2-minus ion in Equation 16.7 plays the conjugate base for the "HNO_2". ---------- ;;; H3O-plus ion in Equation 16.7 acts as the conjugate acid for the H2O molecule. The H3O-plus ion in Equation 16.7 plays the conjugate acid for the H2O molecule. ---------- ;;; The HNO2 molecule becomes the NO2-minus ion. The HNO2 molecule loses a proton in Equation 16.7. Then, the HNO2 molecule is the NO2-minus ion. ---------- ;;; The H2O molecule becomes the H3O-plus ion. The H2O molecule gains a proton in Equation 16.7. Then, the H2O molecule is the H3O-plus ion. ---------- NH3 reacts with H2O in Equation 16.8. ---------- Equation 16.8 is "NH_3(aq) + H_2O(l) <--> NH_4^+(aq) + OH^-(aq)". ---------- ;;; The NH3 molecule in Equation 16.8 acts as a Bronsted-Lowry base. The NH3 molecule in Equation 16.8 plays a Bronsted-Lowry base. ---------- ;;; The H2O molecule in Equation 16.8 acts as a Bronsted-Lowry acid. The H2O molecule in Equation 16.8 plays a Bronsted-Lowry acid. ---------- ;;; NH4-plus ion in Equation 16.8 acts as the conjugate acid for the NH3 molecule. ;;; The "NH_4^+" in Equation 16.8 plays the conjugate acid for the NH3 molecule. The "NH_4" in Equation 16.8 plays the conjugate acid for the NH3 molecule. ---------- ;;; OH-minus ion in Equation 16.8 acts as the conjugate base for the H2O molecule. The OH-minus ion in Equation 16.8 plays the conjugate base for the H2O molecule. ---------- ;;; The NH3 molecule becomes the NH4-plus ion. The NH3 molecule gains a proton in Equation 16.8. Then, the NH3 molecule is the NH4-plus ion. ---------- ;;; The H2O molecule becomes the OH-minus ion. The H2O molecule loses a proton in Equation 16.8. Then, the H2O molecule is the OH-minus ion. ---------- ;;; Some acids are better proton donors than other acids. ;;; [Too difficult to reformulate] ;;; Some bases are better proton acceptors than other bases. ;;; [Too difficult to reformulate] The conjugate base of a strong proton donor is a weak proton acceptor. ---------- The conjugate acid of a strong proton acceptor is a weak proton donor. ---------- ;;; A stronger acid has a weaker conjugate base. A strong acid has a weak conjugate base. ---------- ;;; A stronger base has a weaker conjugate acid. A strong base has a weak conjugate acid. ---------- ;;; A stronger acid is a better proton donor. A strong acid is a good proton donor. ---------- ;;; A stronger base is a better proton acceptor. A strong base is a good proton acceptor. ---------- ;;; In water a strong acid completely transfers the acid's protons to the water. ;;; The transfer leaves no undissociated acid molecules in the aqueous solution. A strong acid is in some water. The strong acid transfers the acid's protons to the water. There are zero undissociated acid molecules in the aqueous solution. ---------- ;;; In water the conjugate base of a strong acid almost never accepts protons from the water. ;;; The conjugate base of a strong acid almost never accepts protons from the water. ;;; In water a weak acid partly transfers the acid's protons to the water. ;;; A weak acid partly transfers the acid's protons to the water. A weak acid transfers the acid's protons to the water. ---------- The transfer leaves a mixture of acid molecules and acid ions in the aqueous solution. ---------- ;In water the conjugate base of a weak acid accepts a small percent of the water's protons. The conjugate base of a weak acid accepts a small percent of the water's protons. ---------- The conjugate bases of weak acids are weak bases. ---------- Substances with negligible acidity contain hydrogen. ---------- CH4 is a substance with negligible acidity. ---------- The conjugate bases of substances with negligible acidity are strong bases. ---------- ;;; Strong bases react completely with water. Strong bases react with water. ---------- ;;; Strong bases take protons from the water in the reaction. Strong bases acquire protons from the water in the reaction. ---------- The reaction converts water molecules to OH-minus ions. ---------- ;;; A strong acid is completely ionized in H2O. A strong acid is ionized in H2O. ---------- ;;; A strong base is completely protonized in H2O. A strong base is protonized in H2O. ---------- HCl is a strong acid. ---------- The conjugate base of HCl is Cl-minus. ---------- Cl-minus is a negligible base. ---------- HCl is weaker than H2SO4. ---------- H2SO4 is a strong acid. ---------- The conjugate base of H2SO4 is HSO4-minus. ---------- HSO4-minus is a negligible base. ---------- HSO4-minus is stronger than Cl-minus. ---------- H2SO4 is weaker than HNO3. ---------- HNO3 is a strong acid. ---------- The conjugate base of HNO3 is NO3-minus. ---------- NO3-minus is a negligible base. ---------- NO3-minus is stronger than HSO4-minus. ---------- HNO3 is weaker than H3O-plus. ---------- H3O-plus is a moderate acid. ---------- The conjugate base of H3O-plus is H2O. ---------- H2O is a very weak base. ---------- H2O is stronger than NO3-minus. ---------- H3O-plus is weaker than HSO4-minus. ---------- HSO4-minus is a weak acid. ---------- The conjugate base of HSO4-minus is SO4-minus-2. ---------- SO4-minus-2 is a weak base. ---------- SO4-minus-2 is stronger than H2O. ---------- HSO4-minus is weaker than H3PO4. ---------- H3PO4 is a weak acid. ---------- The conjugate base of H3PO4 is H2PO4-minus. ---------- H2PO4-minus is a weak base. ---------- H2PO4-minus is stronger than SO4-minus-2. ---------- H3PO4 is weaker than HF. ---------- HF is a weak acid. ---------- The conjugate base of HF is F-minus. ---------- F-minus is a weak base. ---------- F-minus is stronger than H2PO4-minus. ---------- HF is weaker than HC2H3O2. ---------- HC2H3O2 is a weak acid. ---------- The conjugate base of HC2H3O2 is C2H3O2-minus. ---------- C2H3O2-minus is a weak base. ---------- C2H3O2-minus is stronger than F-minus. ---------- HC2H3O2 is weaker than H2CO3. ---------- H2CO3 is a weak acid. ---------- The conjugate base of H2CO3 is HCO3-minus. ---------- HCO3-minus is a weak base. ---------- HCO3-minus is stronger than C2H3O2-minus. ---------- H2CO3 is weaker than H2S. ---------- H2S is a weak acid. ---------- The conjugate base of H2S is HS-minus. ---------- HS-minus is a weak base. ---------- HS-minus is stronger than HCO3-minus. ---------- H2S is weaker than H2PO4-minus. ---------- H2PO4-minus is a weak acid. ---------- The conjugate base of H2PO4-minus is HPO4-minus-2. ---------- HPO4-minus-2 is a weak base. ---------- HPO4-minus-2 is stronger than HS-minus. ---------- H2PO4-minus is weaker than NH4-plus. ---------- NH4-plus is a weak acid. ---------- The conjugate base of NH4-plus is NH3. ---------- NH3 is a weak base. ---------- NH3 is stronger than HPO4-minus-2. ---------- NH4-plus is weaker than HCO3-minus. ---------- HCO3-minus is a weak acid. ---------- The conjugate base of HCO3-minus is CO3-minus-2. ---------- CO3-minus-2 is a weak base. ---------- CO3-minus-2 is stronger than NH3. ---------- HCO3-minus is weaker than HPO4-minus-2. ---------- HPO4-minus-2 is a weak acid. ---------- The conjugate base of HPO4-minus-2 is PO4-minus-3. ---------- PO4-minus-3 is a weak base. ---------- PO4-minus-3 is stronger than CO3-minus-2. ---------- HPO4-minus-2 is weaker than H2O. ---------- H2O is a very weak acid. ---------- The conjugate base of H2O is OH-minus. ---------- OH-minus is a moderate base. ---------- OH-minus is stronger than PO4-minus-3. ---------- H2O is weaker than OH-minus. ---------- OH-minus is a negligible acid. ---------- The conjugate base of OH-minus is O2-minus. ---------- O2-minus is a strong base. ---------- O2-minus is stronger than OH-minus. ---------- OH-minus is weaker than H2. ---------- H2 is a negligible acid. ---------- The conjugate base of H2 is H-minus. ---------- H-minus is a strong base. ---------- H-minus is stronger than O2-minus. ---------- H2 is weaker than CH4. ---------- CH4 is a negligible acid. ---------- The conjugate base of CH4 is CH3-minus. ---------- CH3-minus is a strong base. ---------- CH3-minus is stronger than H-minus. ---------- Equation 16.9 is "HX(aq) + H_2O(l) <--> H_3O^+(aq) + X^-(aq)". ---------- Proton-transfer reactions are governed by the relative strengths of the two bases. ---------- The symbol "HX" denotes an acid in Equation 16.9. ---------- "HX" dissolves in water in Equation 16.9. ---------- Concurrent with the dissolving, a proton transfer occurs. ---------- H2O is the base in the forward reaction in Equation 16.9. ---------- H2O removes the proton from "HX" in the reaction in Equation 16.9. ---------- The reaction produces H3O-plus and X-minus. ---------- ;Therefore, the equilibrium is on the right side of Equation 16.9. The equilibrium is on the right side of Equation 16.9. ---------- Equation 16.9 describes the behavior of a strong acid in water. ---------- Equation 16.10 is "HCl(g) + H_2O(l) --> H_3O^+(aq) + Cl^-(aq)". ---------- HCl dissolves in water in Equation 16.10. ---------- ;;; The solution produced by the dissolving consists almost entirely of H3O-plus ions and CL-minus ions. The solution produced by the dissolving contains H3O-plus ions and CL-minus ions. ---------- The solution has a negligible concentration of HCl molecules. ---------- H2O is stronger than Cl-minus. ---------- ;Therefore, H2O acquires the proton. H2O acquires the proton. ---------- The H2O molecule changes into the hydronium ion in the equation. ---------- Equation 16.11 is "HC_2H_3O_2(aq) + H_2O(l) <--> H_3O^+(aq) + C_2H_3O_2^-(aq)". ---------- ;[Assume that] "HX" is a weak acid in Equation 16.11. "HX" is a weak acid in Equation 16.11. ---------- The equilibrium is on the left side of Equation 16.11. ---------- HC2H3O2 is acetic acid. ---------- ;;; An aqueous solution of acetic acid consists mainly of HC2H3O2 molecules. An aqueous solution of acetic acid consists of HC2H3O2 molecules. ---------- An aqueous solution of acetic acid has relatively few H3O-plus ions and C2H3O2-minus ions. ---------- C2H3O2-minus is stronger than H2O. ---------- ;Therefore, C2H3O2-minus abstracts the proton from H3O-plus. C2H3O2-minus removes the proton from H3O-plus. ---------- ;;; The proton transfers to the stronger base in every acid-base reaction. ;;; The proton transfers to the stronger base in a acid-base reaction. The proton transfers to the strongest base in a acid-base reaction. ---------- ;;; The equilibrium is on the side with the weaker base in every acid-base equation. ;;; The equilibrium is on the side with the weaker base in a acid-base equation. The equilibrium is on the side with the weakest base in a acid-base equation.