3.1.1.12 Defining acids and bases

1. The pH scale measure…

•Alkali’s are soluble …2?

Info: pH7= …3?. Below pH7 is…4? And above 7 is …5?.

•An acid reacts with a base to form…6? (Acid + base → salt + water) → The products of the reaction are closer to pH 7 so we call it a …7? Reaction.

8. What experimental technique can we use to carry out neutralisation reactions to find the concentrations of acids and bases?

9. What are the 3 types of base?

10. What is the reaction between metal hydroxides and acids?

11. What is the reaction between Metal oxides and acids?

12. What is the reaction between metal carbonates and acids?

13. An acid reacts with a metal to form…

(acid + metal → salt + hydrogen)

1. How acidic or basic something is

2. Base

3. Neutral

4. Acidic

5. Basic

6. Salt + Water

7. Neutralisation

8. Titration

9. Metal oxide(e.g.K2O), metal hydroxide(NaOH) , metal carbonate(CaCO3)

10. Metal hydroxide(s) + acid(aq) → Salt(aq) + water(l)

11. Metal oxide(s) + acid(aq) → Salt(aq) + water(l)

12. Metal carbonate(s) + acid(aq) → Salt(aq) + water(l) + CO2(g)

13. Salt + hydrogen (g)

Bases and Alkali

1. Answer image question?

note: All alkalis are bases but not all bases are alkali.

Info: If we have a alkali in solution we call it an alkaline solution.

• An alkali is a base that is soluble in …2?

(Other side image contains info)

3. What is the correct formula for iron (III) hydroxide?

4. What is the correct formula for phosphoric acid?

   
   

1. A and B

2. Water

3. Fe(OH)3

4. H3PO4

The Arrhenius Model

1. Which two ions does hydrochloric acid dissociate into in water?

2. Hydrogen cations, or H+ ions, are also known as…

3. Sodium hydroxide, NaOH, dissociates into two different ions. The cation is...3?

and the anion is …4?

According to the Arrhenius model, why is a solution of sulphuric acid (H2SO4) acidic?

A: Sulphuric acid has a pH of less than 7.

B: When it dissolves, sulphuric acid releases H+ ions into water.

•Arrhenius discovered that when substances dissolve, they …6? into …7?. According to the Arrhenius model of acids and bases, acids add …8? to water, and bases add …9? to water.

1. H+ And Cl−

2. Protons

3. Na+

4. OH-

5. B(Arrhenius acids- any substance that adds H+ ions to water)

6. Dissociate

7. Ions

8. H+

9. OH-

   
   

The Bronsted-Lowry Model

1. HNO3+NaOH→NaNO3+H2O
   In this reaction, the substance that is donating a proton is…

According to the Brønsted-Lowry model, an acid is a …2?  and a base is a …3?

4. Consider the following reaction:
   Ca(OH)2b(s) + 2HNO3 (aq) → Ca(NO3)2 (aq) + 2H2O (l)
   Identify the acid and base according to the Brønsted-Lowry model.
   
   5. Consider the following reaction:
   HCl (aq)+LiOH (aq)→LiCl (aq)+H2O (l)
   Identify the acid and base according to the Brønsted-Lowry model.

   6. Consider the following reaction:
      
      HBr (g)+NH3(g)→NH4Br (s)
      
      Identify the acid and base according to the Brønsted-Lowry model.

   7. Consider the following reaction:
      
      HBr (aq)+H2O (l)→H3O+(aq) + Br−(aq)
      
      Identify the acid and base according to the Brønsted-Lowry model.

   8. Consider the following reaction:
      
      CO3 2−(aq) + H2O (l) →HCO3 *−(aq) + OH−(aq)
      
      Identify the acid and base according to the Brønsted-Lowry model.
      
      
      

   9. Answer image question (note Arrhenius bases and acids are all soluble/dissolve in water→ if it isn’t in solution it isn’t an Arrhenius acid or base)
      
      
      

1. HNO3

2. Proton donor

3. Proton acceptor

4. Bron-low acid= nitric acid

   Bron-low base=Calcium hydroxide

5. Bron-low acid= HCl

   Bron-low base=Lithium hydroxide

6. Bron-low acid= hydroponic acid

   Bron-low base=ammonia

(NH3 gained a proton and became NH4 so is a base, whereas HBr donated a proton and became Br so is an acid)

7. Bron-low acid= HBr

   Bron-low base= water

8. Bron-low acid= water

   Bron-low base= Carbonate ion

Differences Between the Models

Note: To tell if a substance is an Arrhenius acid or base we ask these questions

1)Is it soluble in water 2)Does it release H+ ions 3)If no for (q2) then does it release OH- ions. 4) If no then it’s neither an acid or base

1. If compound X dissolves in water and releases hydroxide ions, what must it be?

Note: To tell if a substance is a Bronsted-Lowry acid or base we ask these questions

1)Does it react with something → if no then it can’t be an acid or base

2) If yes(q1), we ask can it donate a proton

3) If no we ask does it accept a proton→ if no Then the substance is neither an acid or base

2. Answer image question

1. Base(according to the Arrhenius model)

Strong and Weak Acids and Bases

1. The process where the ions in a compound separate when the compound dissolves in water is called…

Note: HCl(hydrochloric acid), HNO3(nitric acid) and H2SO4(sulfuric acid) are strong acids

2. When potassium hydroxide is added to water, it fully dissociates into ions. This tells us that potassium hydroxide is a…

Note: NaOH[sodium hydroxide],Ba(OH)2 [barium hydroxide],Ca(OH)2 [Calcium hydroxide] are strong bases

3. Answer image question?

4. When ammonia is added to water, it only slightly reacts with water to produce ions. This tells us that ammonia is a…

5. Water dissociates into H+ and OH- ions but we know that H+ ions don’t exist in their own and react. What ion is created when H+ ions react with water?

   Info: Water also slightly dissociates into ions, forming an acid base equilibrium. (where a water molecule acts as an acid and another acts as a base)

   H2O(l) +H2O (l) → H3O+(aq) + OH-(aq)

6. The first water molecule is acting as a Brønsted-Lowry base because it…

7. The second water molecule is acting as a Brønsted-Lowry acid because it…

•Weak acids …8? dissociate into ions In water. This forms an …9?. Strong acids and strong bases …10? dissociate into ions. Weak bases …11?with water to form an equilibrium.

1. Dissociation

2. Strong base

4. Weak base

5. H3O+(hydronium ions)

6. Accepts a proton to become a hydronium ion

7. Donates a proton to become a hydroxide ion

8. Partially

9. Equilibrium

10. Fully

11. React

Conjugate Acids and Conjugate Bases

Full reaction: NH3(aq) + H2O(l) →←(RR) NH4+(aq) + OH- (aq)

NH3 + H+→NH4+
In this reaction, ammonia is a Brønsted-Lowry …1? because it is a …2?.

NH4+→NH3 + H+
In this reaction, the ammonium ion is a Brønsted-Lowry …3? because it is a …4?

• Based from these examples, when ammonia acts as a bronsted-Lowry base, it form a bronsted-lowry acid, and we call the acid a …5?. So ammonium is the conjugate acid of ammonia.

•So in general, when a substance reacts as a brosnted-Lowry base and accepts a proton, we call the product that forms a conjugate acid.

6. What is the conjugate acid of hydroxide, OH−? (in the full reaction)

info: in the full reaction, we would call the OH- and H2O the conjugate-acid base pair.→This is because we can covert between them by adding a removing a proton (OH-[base] + H+ →←H2O[conjugate acid])

7. Whenever a substance reacts as a Brønsted-Lowry acid and loses a proton, we call the product that forms its conjugate base.
   
   What is the conjugate base of hydrogen fluoride, HF?

Note: Together, we would call the Fluoride and Hydrogen fluoride the conjugate acid base pair or conjugate-pair for short.

8. Answer image question?

9. Whenever a substance acts as a Brønsted-Lowry base, we call the product it forms its…

10. Whenever a substance acts as a Brønsted-Lowry acid, we call the product it forms its…

1. Base

2. Proton acceptor

3. Acid

4. Proton donor

5. Conjugate acid

6. H2O

7. F-

   9. Conjugate acid(note that since these have gained protons[to form itself as the product], they can donate the protons to form the Brownsted-Lowry base again in a RR)

10. conjugate base(Note that since these have lost a proton, they can accept a proton to form the Bronsted-Lowry acid again in a RR)

Acid or Base

Note: When two acids react, the strong acid always acts as the Bronsted-Lowry acid, and the weak acid acts as the Bronsted-Lowry base.

1. Answer image question?

2. H2O + HNO3→H3O+ + NO3−
   In this reaction, water is acting as…

3. H2O + NH3→ NH4+ + OH−
   In this reaction, water is acting as…

1. A (this image shows that even though they are both acids, one can still act as bronsted-Lowry base→ they are both also Arrhenius acids since they dissociate in water)

2. Bronsted-Lowry base( it accepts a proton to become a hydronium ion which is the conjugate acid)

3. Bronsted-Lowry acid(it donates a proton to become OH- which is the conjugate base)

Image info: dissociation of water (note that not all water molecules dissociate into ions so this reversible reaction can occur)

1. Which of the following statements is true?

   A: Whether a substance acts as an Arrhenius acid or an Arrhenius base depends on the reaction that is taking place.

   B: Water can act as a Brønsted-Lowry acid or a Brønsted-Lowry base depending on what it is reacting with.

1. B

1. Answer image question

2. What does corrosive mean?

2. Can burn through living or non-living tissue

1. Answer image question

2. Define the term ‘Brønsted-Lowry base’.

3. Define the term ‘Arrhenius acid’

4. Water is capable of dissociation. Write an equation to show the dissociation of water molecules

According to the Brønsted-Lowry model, acid-base equilibria always contain two acid-base pairs, called …5? Each of these acid-base pairs is made up of a …6? and a …7?. The only difference between them is that the …8?has an extra proton.

2. a substance that accepts a proton in a reaction.

3. a substance that dissolves in water to produce H+ ions (or H3O+ ions).

4. or H2O + H2O⇌H3O+ + OH− or H2O ⇌ H+ + OH-

   
   

5. Conjugate pairs

6. Conjugate acid

7. Conjugate base

   8. conjugate acid

   
   

1. Answer image question?

*Arrhenius discovered that the ions in a compound separate when the compound dissolves in water in a process called...2? →

…3? undergo this process almost fully to produce a solution of protons and anions. →

…4? undergo this process only partially to produce a solution of protons and anions.

5. Ammonium ions, NH4+, can be used as a weak acid in organic reactions. Write an equation for the dissociation of this acid. (Do not include state symbols)

info:When ammonium is used as a weak acid in organic synthesis, the reaction remains reversible because it exists in equilibrium with its conjugate base, ammonia.

Info: If a strong acid dissociates, the process is considered effectively irreversible because the acid completely donates its protons to the solvent, leaving virtually no original acid molecules behind to facilitate the reverse reaction.

2. Dissociation

3. Strong acids

4. Weak acids

5. NH4+⇌H+ + NH3

Answer image question

Answer image question

Acid and base reactions

• Acids can't just throw away their protons — they can only get rid of them if there's a …1? to accept them. In this reaction the acid, HA, transfers a proton to the base, B:

HA (aq) + B(aq) <=> BH+ (aq) + A- (aq)

Its equilibrium is far to the left for weak acids, and far to the right for strong acids.

-It's an equilibrium, so if you add more HA or B, the position of equilibrium moves to the right. But if you add more BH or A-, the equilibrium will move to the left, according to Le Chatelier's principle. When an acid is added to water, water acts as the ..:2? and accepts the proton:

HA (aq) + H2O(aq) <=>H3O+ (aq) + A- (aq)

1. Base

2. Base

The ionic product of water

Read image info:

1. Why does the equilibrium of water dissociation lie to the left?

2. What is Kw?

3. What are the units of Kw always?

   • The value of Kw changes as 4? Changes

   5. what is the expression for Kw?(use this always when asked)

   6. When pure water dissociates,the concentration of [H+] and [OH-] is …, therefore [H+]=[OH-] so when dealing with water the expression for Kw can be written as …7?.

   8. Answer the image questions?

1. Because water only dissociates a tiny amount so there is way more water molecules compared to H+ and Oh- ions.

2. The ionic product of water(basically the equilibrium or constant of water

3. Mol2 dm-6

4. Temperature

5. Kw= [H+][OH-]

6. The same/equal

7. Kw = [H+]*2 or even kw= [OH-]*2 •You must still write the expression in the original way

pH calculations

Read image info

The pH scale is a measure of the …1? ion concentration in a solution.

The concentration of hydrogen ions in a solution can vary enormously, so those wise chemists of old decided to express the concentration on a logarithmic scale.

pH can be calculated using the following equation: …2?

3. If you've got the pH of a solution, and you want to know its hydrogen ion concentration, then you need the inverse of the pH formula which is ..,?

4. Answer image questions?

1. Hydrogen

2. pH= -log10 [H+]

3. [H+] = 10*-pH. (pH value in the indices)

   
   

Strong bases

1. Why do strong acids have a lower pH than weak acids? → Therefore for a strong acid, the concentration of the acid is equal to …2?

Do Now: Read the info in the top image and answer the example question in math skills.

1. Strong acids have a lower pH because they completely ionize in water.(must say the ones in bold)

2. The [H+]-hydrogen ion concentration

pH of strong monoprotic acids

1. What is a monoprotic acid?

E.g. Hydrochloric acid (HCI) and nitric acid (HNO3) are strong acids so they ionise fully shown by the equation …2?

HCl and HNO3 are also monoprotic, so each mole of acid produces one mole of hydrogen ions. This means the H+ concentration is the same as the …3? concentration. So, if you know the concentration of the acid you know the H+ concentration and you can calculate the pH.

Note: You can tell whether a strong acid is monoprotic by looking at the number of Hydrogens in the chemical formula, if it has 1 hydrogen then it’s monoprotic.(The same applies for monoprotic bases so if they have 1 OH- ion then they are monoprotic)

pH of strong diprotic acids

4. What is a diprotic acid?

   Sulfuric acid is an example of a strong diprotic acid( because it has 2 hydrogens in its formula) and when ionizes fully it’s represented by the equation…5? → So diprotic acids produce two moles of hydrogen ions for each mole of acid, meaning that the [H+] is …6? the concentration of the acid.

   7. answer image questions (read the circles box also)

1. An acid that will release 1 proton(H+ion) when it ionizes(dissociates).

2. HCl (aq) → H+ (aq) + Cl- (aq)

3. Acid

4. An acid that will release 2 protons(H+ ions) when it dissociates

5. H2SO4 (aq) → 2H+ (aq) + SO4*2- (aq)

6. Twice

Answer image questions

Weak acids and bases

1. Why do weak acids have a higher pH then a strong acids? → And therefore the concentration of acid is not the same as the concentration of H+ ions/protons.

2. What is the acid dissociation constant for weak acids represented by? → There is no acid dissociation constant for strong acids because …3?

   4. What is the general equation for Weak acid dissociation?

•Assumptions for weak acids

1) 5?

2) Acids split evenly → therefore the concentration of products is the same. [H+] = [A-] → this allows us to simplify the original la formula to a shortened version where [H+] is squared.

Info: read images on both sides for info

1. They ionize partially in water(Aqueous solution)

2. Ka

3. Strong acids ionize fully so there is no equilibrium for the dissociation of strong acids

4. HA <=> H+ + A- (HA is any weak acid) (A- is a negative ion[salt])

5. The concentration at equilibrium is equal to the concentration of the acid at the start of the reaction (since very little dissociates, we can assume the concentration of products is the same as concentration of reactants even though this isn’t necessarily true)

Answer image question?

pKa

Info: Sometimes Ka is a very small number in standard form,so we use pKa to make it a “nicer number”.

1. What is the formula to work out pKa from the ka value, and Ka from the pKa value?

2. Read image info then calculate the math skill question?

1. pKa= -log10(ka)

   Ka= 10*-pKa

Answer image question

Answer image questions

Answer image questions

pH curves and titration