Ch.15 - Acid and Base EquilibriumSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

Identifying Acids and Bases

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Acid Identification

Most acids have one common feature and that is the presence of the hydronium ion, which is represented by H+ or H3O+.

Concept #1: Identifying Binary Acids. 

Binary acids can be identified by the fact that they all possess an H+ ion attached to an electronegative element. 

Oxyacids can be identified by the fact that they all possess an H+ ion connected to a nonmetal and oxygen, hence the prefix “oxy”. 

Concept #2: Identifying Oxyacids. 

They are created by the hydration of nonmetal oxides. 

Conversely, metal oxides create bases when hydrated by water. 

Practice: Which of the following compound(s) cannot be classified as an acid?


Binary Acid Strength

Concept #3: Acids and  Electrolytes

Strong Acids are strong electrolytes that completely dissociate into ions when dissolved in water. 

Weak acids are weak electrolytes that don’t completely ionize, but instead reach a state of equilibrium. 

Concept #4: Strength of Binary Acids.

When looking at a binary acid we look at both electronegativity and size to determine their strength. 

Practice: Which is the weakest acid from the following?

Practice: Which of the following acids would be classified as the strongest?

Oxyacid Strength

The strength of an oxyacid depends on the number of oxygen atoms and the electronegativity of the nonmetal. 

Concept #5: The Strength of Oxyacids.

If your oxyacid has 2 or more oxygens than hydrogens then your oxyacid is a strong acid. 

Concept #6: Comparing the Strength of Oxyacids. 

When comparing the strengths of different oxyacids remember:

If they have different number of oxygens then the more oxygens the more acidic 

 

If they have the same number of oxygens then the more electronegative the nonmetal the more acidic.

 

With some rules there are exceptions. Oxalic acid and Iodic acid have two more oxygens than hydrogens but are weak acids because carbon are iodine have low electronegativity. 

Amphoteric species (compounds that can act as both an acid or a base) are also an exception to the rule for oxyacids. 

Practice: Rank the following oxyacids in terms of increasing acidity. 

a) HClO3

b) HBrO4

c) HBrO3

d) HClO4

Base Strength

Concept #7: Bases and Electrolytes. 

Strong Bases are strong electrolytes that completely dissociate into ions when dissolved in water. 

Weak bases are weak electrolytes that don’t completely ionize, but instead reach a state of equilibrium. 

Bases are characterized by THREE major features: they may possess metals, they may have a negative charge or they may be an amine

Concept #8: Bases and Group 1A. 

Any Group 1A metal when combined with OH , H , O2– or NH2 makes a STRONG BASE.

Concept #9: Bases and Group 2A. 

Group 2A metals, from Ca2+ to Ba2+, when combined with OH , H , O2– or NH2 makes a STRONG BASE. 

Amines are compounds with only nitrogen or hydrogen (i,e. NH3) or with carbon, nitrogen and hydrogen (i,e. CH3NH2). 

Concept #10: Amines. 

Neutral Amines are considered weak bases

Positive Amines are considered weak acids

Example #1: Classify each of the following as a strong acid, weak acid, strong base or weak base:

a)   HCHO2                                                        c)   H2NNH2

b)   (CH3CH2)3NH+                                       d)   HBrO3

Practice: Classify each of the following as a strong acid, weak acid, strong base or weak base.

Practice: Classify each of the following as a strong acid, weak acid, Strong base, or weak base. 

Practice: Classify each of the following as a strong acid, weak acid, strong base or weak base.

Additional Problems
Which of the following cannot be an acid? a. HCN           b) H2SO3              c)  C6H5OH       d)  C5H12           e) All are acids.
Which of the following statements is/are correct? a)  CH3OH is an Arrhenius Base. b)  BF3 is a Bronsted-Lowry Acid. c)  NH4+ is a Bronsted-Lowry Base. d)  CN – is a Lewis Base. 
Which of the following solutions will have the highest concentration of hydronium ions? 0.250 moles CH3COOH 0.250 moles CH2ClCOOH 0.250 moles CHCl2COOH 0.250 moles CCl3COOH They would all have equal concentrations of hydronium ions  
Identify the weakest acid. A) HF B) HCl C) HBr D) HI E) not enough information is available
Chlorine forms four oxyacids.  Two of these are HClO 2 and HClO4.  Of these a. HClO2 is a strong acid and HClO4 is a weak acid.  b. HClO4 is a strong acid and HClO2 is a weak acid.  c. Both HClO2 and HClO4 are strong acids.  d. Both HClO2 and HClO4 are weak acids. 
Rank the following​ oxyacids in terms of increasing acidity. a) HNO3                                         b) HBrO4                                 c) H2CO3                                 d) HClO4
Which is the strongest acid from the following? a) H 2S                      b) HF                      c) H 2Te                    d) H 2O                    e) NH 3
Which of the following lists contain both a strong acid and a strong base? i. KBr and CH3OH ii. HCIO4 and NaH iii. HNO3 and KOH a. i only b. ii only c. iii only d. ii and iii e. i, ii and iii
Which of the following lists contains both a strong acid and a strong base? i. HI and Na2O ii. HCl and C3H7OH iii. HBrO3 and LiOH A. i only B. ii only C. iii only D. ii and iii E. i and iii
Which of the following statements is true about an acidic solution at 25  oC i. [H3O+] > [OH – ] ii. pH > 7 iii. [H3O+][OH – ] = 1.0 X 10 -14 A. i only B. iii only C. i and ii D. i and iii E. ii and iii
Knowing if you have a weak or strong acid or base is important in determining if you use an ICE Chart or not. 
Below is a list of salts/molecules that we are going to throw in water. Based on their structure/properties, arrange the following species: KCl    H2SO4   CF3COOH     CH3COOH   NaCN ______ < _____ < _____< ______ < _______ From weakest to strongest acid. 
The reason HI is a stronger acid than HCl is because      A) the difference in electronegativity gets larger as the atoms get farther apart on the periodic table. B) electronegativity increases as you go up the periodic table. C) the bond strength decreases down a group in the periodic table. D) anion radius decreases as you go down the periodic table. E) HI is an Arrehnius acid and HCl is not.
Of the following, which is the weakest acid?      A) HIO           B) HIO 2          C) HIO 3          D) HIO 4    E) The acid strength of all of the above is the same.
Which of the following acids will be the strongest?      A) H2SO4                    B) HSO4−        C) H2SO3        D) HSO3−        E) H2SeO4
Which indication of relative acid strengths is INCORRECT?       A) HClO2 > HClO B) H2SO4 > H2SO3 C) HCl > HF D) H2SO3 > HNO3
List the following acids in order of increasing strength:             H2SO4             H2SeO4           H2TeO4       A) H2SO4 < H2SeO4 < H2TeO4 B) H2SeO4 < H2SO4 < H2TeO4 C) H2SeO4 < H2TeO4 < H2SO4 D) H2TeO4 < H2SeO4 < H2SO4 E) H2SO4 < H2TeO4 < H2SeO4
Which of the following list contains both a strong acid and a strong base? i. HBr and CH3OH ii. HClO4 and NaH iii. HNO3 and KOH A. i only B. ii only C. iii only D. ii and iii E. i and iii
Place the following in order of increasing acid strength.      HBrO2      HBrO3       HBrO      HBrO 4 A) HBrO2  <  HBrO4  <  HBrO   <  HBrO3 B) HBrO    <  HBrO2  <  HBrO3  <  HBrO4 C) HBrO2  <  HBrO3   <  HBrO4  <  HBrO D) HBrO4  <  HBrO2   <  HBrO3   <  HBrO E) HBrO    <  HBrO4   <  HBrO3   <  HBrO2
Which of the following is a  STRONG acid? A) C6H5CO2H B) HCN C) HClO4 D) NH4+ E) H2O
Which of the following is  TRUE? A) A neutral solution contains [ H 2O ] = [ H 3O+ ] B) A neutral solution does not contain any H 3O+ or OH- C) An acidic solution has [ H 3O+ ] > [ OH - ] D) A basic solution does not contain H 3O+ E) None of the above are true.  
Which one of the following is a strong acid? A) H2CO3 B) H2SO3 C) H2SO4 D) H3PO4 E) CH3COOH
Which one of the following is a strong base? A) LiOH B) CH3COOH C) NH3 D) H3PO4 E) HClO2
The following compounds given below are all acids What common features would help you identify these compounds as acids? Circle the acidic hydrogen on all compounds. Match the name with the acid. a) benzoic acid b) hydrochloric acid c) acetic acid d) nitrous acid e) nitric acid f) formic acid g) hydrocyanic
The following compounds are all bases: What common features would help you identify these compounds as bases? Match the name with the base: a) barium hydroxide b) ammonia c) trimethyl amine d) potassium hydroxide e) sodium hydroxide f) phenyl amine (aniline)
Based on your observations of some common acids and bases, predict whether the following compounds are acids or bases and why:
Order the following acids in increasing acid strength. A.  HI < HF < HBr < HCl B.  HF < HCl < HBr < HI C.  HBr < HF < HI < HCl D.  HCl < HF < HBr < HI E.  HBr < HCl < HI < HF
Arrange the compounds in order of increasing acid strength A.  HClO4 < HClO < HClO2 < HClO3 B.  HClO < HClO2 < HClO4 < HClO3 C.  HClO2 < HClO3 < HClO4 < HClO D.  HClO3 < HClO4 < HClO < HClO2 E.  HClO < HClO2 < HClO3 < HClO4
Select the strong acid from the set a-e. a) NaOH b) HOCl c) H2S d) HF e) HNO3
Which of these compounds can be classified as a strong base? a) NH3 b) CuCl c) CsOH d) H2CO3 e) Ni(OH)2
Which of the following is the most acidic: HBrO 3, HFO3, HIO3, and HClO3? A) HBrO3 B) HFO3 C) HIO3 D) HClO3 E) none of the above
Which of the following can accept a H+ from water to form a polyatomic ion? HCl, H2O, NH3, KOH a) KOH only b) H2O and HCl c) HCl and KOH d) NH3 and H2O e) HCl and NH3
Which of the following can donate a proton, H + , to water? NaCl, AgNO3, NH3, HNO3 a) NaCl b) AgNO3 c) HNO3 d) NH3 and NaCl e) AgNO3 and NH3
Which of the following statements is/are true? i. HNO3 is a strong acid ii. NaH is a strong base iii. HCIO2 is a strong acid a. i only  b. iii only c. i and iii d. i and ii e. ii and iii
Select the compound that is most likely a weak base. a) LiOH b) HCl c) CH3CO2H d) Sr(OH)2 e) NH3
Which of the following compounds is the most acidic?    A) HClO4    B) HClO3    C) HClO2    D) HClO
Which of the following is a weak acid? A)  H2SO4             B)  HNO3                              C)  HF                                    D)  HBr                                 E)  HCl
Which of the following is a strong acid? A)  H3PO4             B)  HNO3                              C)  HF                                    D)  CH3COOH                     E)  H2O
Which of the following is a weak base? A)  NH3                 B)  Ca(OH)2                         C)  Ba(OH)2                         D)  NaOH                             E)  CH3COOH
When it comes to naming acids we must follow these rules. Naming ACIDS. 1)  BINARY ACIDS                   Features:   HYDROGEN  +   NONMETAL(S)  +  NO OXYGEN Rules for Naming: The prefix will be hydro-. Use the root of the nonmetal as the base name. The suffix will be –ic acid. a. HCN                                                                           b. Hydrotelluric acid         2)  OXOACIDS or OXYACIDS             Features:   HYDROGEN +  POLYATOMIC ION W/ OXYGEN Rules for Naming: When naming oxyacids, if the polyatomic ion ends with –ate then change the ending to –ic acid. When naming oxyacids, if the polyatomic ion ends with –ite then change the ending to –ous acid.  a. HNO2                                      b. Carbonic acid                          c. Sulfurous acid
Acid rain consists primarily of ________. A) nitric and sulfuric acids B) sulfuric acid C) nitric acid D) acetic acid E) benzoic acid
The common constituent in all acid solutions is A)  H2                    B)  H+                     C)  OH–                 D)  H2SO4             E)  Cl–
When comparing acids with a formula HA, where A can be any one element, what is the trend in terms of acid strength? A. Increases as A goes toward the top, left of the periodic table B. Increases as A goes toward the top, right of the periodic table C. Increases as A goes toward the bottom, left of the periodic table D. Increases as A goes toward the bottom, right of the periodic table
Which of the following solutions will have the lowest pH? a) 0.10 M H3PO3 b) 0.10 M HF c) 0.10 M HC2H3O2 d) 0.10 M HBrO3 e) 0.10 M HClO2
Which of the following solutions will have the  lowest concentration of hydronium ions?  a) 0.100 moles C6H5NH2 b) 0.100 moles Be(OH)2 c) 0.100 moles SrH2 d) 0.100 moles (CH3)2NH  
Which is the strongest acid? (a) H2O   (b) H2Se   (c) H2Te   (d) H2S
Acid strength decrease in the series HI > HSO4- > H2CO3 > HCN. Which of these anions is the weakest base? A) I- B) SO42- C) F- D) CN- E) HCO3-
Place the following in order of increasing acid strength (weakest to strongest).            HBr            H  3PO3            H 3PO4 A) HBr            < H 3PO3       < H3PO4 B) HBr            < H 3PO4       < H 3PO3  C) HBr             < HBrO 3       < HBrO4 D) H3PO3        < H3PO4       < HBr E) H3PO4         < H3PO3        < HBr
Which acid is stronger? 1. They have the same strength. 2. HBrO 3. HBrO3
Which of the following is described incorrectly? A. sodium hydroxide is a strong base B. hydrochloric acid is a strong acid C. phosphoric acid is a strong acid D. acetic acid is a weak acid E. ammonia is a weak base
If Ka of HXO3 is > than Ka of HZO3 at 25°C, then it is most likely that:a. X is more electronegative than Zb. X exhibits a higher oxidation state than Zc. The H―X bond is weaker than the H―Z bondd. HXO3(aq) + ZO3−(aq) ⇌ XO3−(aq) + HZO3(aq) is reactant-favored at 25°Ce. Z is larger than X
Of the following acids, __________ is not a strong acid.      A) H 2SO 4        B) HNO 3          C) HCl           D) HNO 2         E) HClO 4
Nitric acid is a strong acid, but nitrous acid is a weak acid. Why? 
Rank the acids from strongest to weakest, overlap them if they are equivalent:HClHlLiHH2S
When dissolved in water, of HClO4, NH3, KOH, Hl, and CH3OH which are acids?a. HClO4 and Hlb. NH3 and KOHc. Only KOHd. Only Hl
Rank the following compounds in order of decreasing acid strength using periodic trends. Rank the acids from strongest to weakest. To rank items as equivalent, overlap them. H2Se HBr H2O HI
Consider three generic acids: HX, HY, and HZ. Rank these acids according to strength.
Which of the following statements(s) is/are correct i. Strontium amide, Sr(NH2)2,is a weak base. ii. Dichromic acid H2Cr2O7 is a strong acid. iii. Potassium oxide, K2O, is a strong base A. i only B. ii only C. iii only D. i and iii E. ii and iii
Rank the oxoacids of chlorine according to strength.HClO3, HClO4, HClO, HClO2
In aqueous solution, classify these compounds as strong acids, weak acids, strong bases, weak bases, or other:HNO3, HCl, H3PO4, HCN, NaOH, Ba(OH)2, CH3NH2, NH3, CH3COOH, NaCl
Arrange the compounds in order of increasing acid strength A) HClO4  < HClO < HClO2  < HClO3 B) HClO < HClO2  < HClO4  < HClO3 C) HClO2  < HClO3  < HClO4  < HClO D) HClO3  < HClO4  < HClO < HClO2 E) HClO < HClO2  < HClO3  < HClO4
Which of the following is not a property of an acid? a) Acids have a slippery feel. b) Acids have a sour taste. c) Acids dissolve many metals. d) Acids turn litmus paper red. e) All of the above are properties of acids.
Complete the following sentences about strong and weak acids and bases. Strong acids are generally either hydrohalic acids (ex. _____) or oxoacids in which the number of oxygen atoms exceeds the number of ionizable _____ by 2 or more (ex. HNO3). Weak acids are usually one of the following: 1. hydrofluoric acid, _____, 2. acids in which the proton is not bonded to an oxygen atom or a halogen (ex. _____), 3. _____ where the number of oxygen atoms equals or only exceeds by 1 the number of ionizable _____ (ex. _____) or 4. _____ (ex. _____). Strong bases are _____ of group _____ metals (ex. _____) or larger group _____ metals (ex. _____), or oxides of the same metals. Weak bases are usually compounds containing a nitrogen atom with _____ bond(s) and 1 lone pair(s) (ex. _____).
What is an acid and what is a base? An acid–base reaction is sometimes called a proton-transfer reaction. Explain.
Arrange the following oxoacids in order of decreasing acid strength. Rank from strongest to weakest acid. To rank items as equivalent, overlap them. HClO3, HClO2, HClO, HBrO
A substance that contains hydrogen that may be replaced by a metal is a/an a. nonmetal. b. colloid. c. acid. d. base.
Classify each substance as a strong acid, strong base, weak acid, or weak base. HCl KOH HCN HF CH3NH2 CsOH HBr LiOH Ba(OH)2 H2SO4
Salt is the product formed by a reaction in which _______ atoms of an acid are replaced by the atoms of a metal. a. nitrogen b. hydrogen c. oxygen d. carbon
Classify each substance as a strong acid, strong base, weak acid, or weak base. HCCOH HClO4 HI NH3 NaOH HNO2 CH3COOH (CH3)2NH HNO3 Ca(OH)2  
Classify each substance as a strong acid, strong base, weak acid, or weak base. HCCOH, HClO4, HI, NH3, NaOH, HNO2, CH3COOH, (CH3)2NH, HNO3, Ca(OH)2, HCl, KOH, HCN, HF, CH3NH2, CsOH, HBr, LiOH, Ba(OH)2, H2SO4
Classify each of the following acids as strong or weak. If the acid is weak, write an expression for the acid ionization constant (Ka).a. HFb. HCHO2c. H2SO4d. H2CO3
Consider the following reaction: HCO3-(aq) + H2O(l) ⇌ H2CO3(aq) + OH -(aq) Which of the following statements is TRUE? a) HCO3- is not an acid and thus the equation is incorrect. b) The reaction of HCO3- with H2O produces H3O+ rather than OH - c) HCO3- is the base and H2O is the acid. d) HCO3- is the acid and OH - is its conjugate base. e) H2O is the base and H2CO3 is its conjugate acid
Arrange the following oxoacids in order of decreasing acid strength. Rank from strongest to weakest acid. To rank items as equivalent, overlap them. HClO2, HClO, HBrO, HClO3
Rank the following compounds in order of decreasing acid strength using periodic trends. Rank the acids from strongest to weakest. To rank items as equivalent, overlap them. HBr, H2O, HCl, LiH
Rank the following compounds in order of decreasing acid strength using periodic trends. Rank the acids from strongest to weakest. To rank items as equivalent, overlap them. BH3, HBr, H2Se, H2S
Which of the following is the strongest acid?a. HBrOb. HBrO4c. HBrO3d. HBrO2
Which of the following are oxoacids (also known as oxyacids)? Check all that apply.a. HFb. HClc. HCNd. H3PO4e. Ba(OH)2 f. Chloric acidg. Nitrous acid
Assuming equal concentrations, rank these solutions by pH. Highest pH(1) Lowest pH(5) RbOH(aq), Sr(OH)2(aq), HCl(aq), HF(aq), NH3(aq), from highest to lowest.
Assuming equal concentrations, rank these solutions by pH. Ca(OH)2(aq), LiOH(aq), NH3(aq), HBrO(aq), HBr(aq)
Assuming equal concentrations, rank these solutions by pH from highest pH to lowest pH Sr(OH)2(aq), NaOH(aq), NH3(aq), HBrO(aq), HBr(aq) Please explain with explanation.
Rank the following compounds in order of decreasing acid strength using periodic trends. Rank from strongest to weakest. HCl, HI, NaH, LiH
Which of the following is a  strong acid?a. C6H5CO2Hb. HCNc. HNO2d. HNO3e. H2O
Rank the following acids from weakest to strongest based on their molecular structure. HClO3, HBrO3, HClO4
Rank the oxoacids of bromine according to strength. (strongest-weakest) HBrO4 HBrO3 HBrO2 HBrO  
Rank the following solutions in order of decreasing [H3O+]. Rank solutions from largest to smallest [H3O+]. To rank items as equivalent, overlap them. 0.10 M HBr 0.10 M HNO2 0.10 M HClO 0.10 M HCN
Part A  Arrange the following oxoacids in order of decreasing acid strength. Rank from strongest to weakest acid. To rank items as equivalent, overlap them. 1. HClO2 2. HClO3 3. HBrO 4. HClO Part B Arrange the following carboxylic acids in order of decreasing acid strength. 1. CHCl2COOH 2. CH2ClCOOH 3. CH3COOH 4. CH3CH2COOH   Part C Arrange the following amines in order of decreasing base strength.   1. CH3NH2 2. NH3 3. NH2Br 4. (CH3)2NH  
In the reaction HF + H2O → F- + H3O+ which is the acid and which is the base? 
Classify these compounds as acid, base, salt, or other. Drag the appropriate items to their respective bins.
Which of the following is the strongest base?a. HOMgBrb. H2Oc. CH4d. CH3OHe. CH3MgBr
Rank the oxoacids of iodine according to strength. (strongest-weakest) HIO4 HIO HIO3 HIO2
In aqueous solution, classify these compounds as strong acids, weak acids, strong bases, weak bases, or other.
Assuming equal concentrations, rank these solutions by pH. 
In aqueous solution, classify these compounds as strong adds, weak acids, strong bases, or weak bases.
What are the weak acid/weak base pair for this experiment?a. HCI/NaOHb. HCH3CO2/NaOHc. CH3CO2/NaOHd. HCH3CO2/CH3CO2