Properties of Acids & Bases

Question 1

What chemical substances are classified as?

Answer 1

Acidic, Basic and Neutral

Question 2

What is the classification based upon?

Answer 2

Concentration of hydrogen ion [H+] or hydronium ions produced when the substance is dissolved in water

Question 3

How are hydronium ion formed?

Answer 3

Hydronium ions form when the hydrogen ion bonds to the water molecule by sharing one of the electron pairs of oxygen pairs. This is called a coordinate covalent bond.

Question 4

What type of bond is created when hydronium is formed?

Answer 4

Covalent coordinate bond: a type of covalent bond in which one atom provides the shared electron bonding pair

Question 5

Name the common acids?

Answer 5

Vinegar, soft drink, lemon juice, car battery acid

Question 6

Name some common bases.

Answer 6

Oven cleaners, ammonia cleanser, baking soda, washing soda

Question 7

Name some neutral substances.

Answer 7

Pure water, sugar solution, pure alcohol solution, sodium chloride solution

Question 8

Identify the name of H3Po4

Answer 8

Phosphoric acid

Question 9

Is phosphoric acid weak or strong?

Answer 9

Weak

Question 10

What is NaHCO3?

Answer 10

Sodium Hydrogen Carbonate

Question 11

What are the acid-base indicators?

Answer 11

Natural or synthetic chemical dyes that change colour depending on the acidity of the surroundings

Question 12

Are the colour changes reversible using indicators?

Answer 12

Yes, they are reversible.

Question 13

What does the reaction of acid and base make?

Answer 13

Salt and water - neutralisation

Question 14

Is neutralisation an exothermic reaction?

Answer 14

Yes, it does release energy/heat to the surroundings.

Question 15

Name three examples that I can reference when told to give an application of a neutralization reaction.

Answer 15

1. Antacid tablets
2. Swimming Pool Acidity
3. Soil Acidity

Question 16

Explain the application of antacid tablets as a neutralisation reaction.

state the chemical equation

Answer 16

Our stomachs contain gastric juices, which HCl is a major compontent of it. Some ppl suffer from gastric reflux where it irritates them in their oesophagus. Neut. can be used to reduce the symptons through commerical tablets called antacids. These antacids contain a weal base such as a magnesium hydroxide, etc.

Mg(OH)2 + 2H3O+ –> Mg2+ +4H2O

Question 17

Explain how swimming pool acidity is managed.

Answer 17

NaOCl (Sodium Hypochlorite) is added to the pool to kill bacteria, reacts with the water to produce hypochlorous acid HOCl and hydroxide ions. The pool becomes alkaline with the increase of OH. HCl is then added in small amounts to neutralise the water - maintian a pH of 7.

Question 18

What is the first thing you do in a calculation equation?

Answer 18

Write the chemical equation

Question 19

How do you calculate the enthalpy of the solution?

Answer 19

1. Temp change
2. mass
3. q=mCAT
4. n=CV
   delta H = -q/n

Question 20

What does Lavoisier’s definition?

Answer 20

Acids were caused by oxygen molecules when dissolved in water.
- He could not explain how metal oxides were not acidic

Question 21

What does Humphry Davy’s definition state?

Answer 21

He found out through conducting his experiment with HCl and metals, the idea that acids could contain hydrogen.
- He could not explain why other hydrogen compounds were not acidic.

Question 22

What was Arrhenius’s definition?

Answer 22

Arrhenius’s theory stated that the acid is a substance that ionises in solution to produce hydrogen ions, whilst a base ionises in solution to produce hydroxide ions.

Question 23

What are some limitations to the Arrhenius model?

Answer 23

• Applies to only aqueous solns
• Accounts for substances which already have H+ and OH-
• Cannot explain how some amphoteric substances can act as both acid and a base

Question 24

What did Arrhenius successfully explain?

Answer 24

Explained the difference between strong acids and weak acids as being due to the their different degrees of dissociation in water.

Question 25

How do you find the percentage dissociation?

Answer 25

% dissociation = [H+]//[HA] x 100%
HA <–> H+ +A-

Question 26

How do you differentiate between strong and weak acids?

Answer 26

Strong acids such as NaOH and KOH are ionic compounds that completely dissociate into free ions in water to produce high concentrations of hydroxide ions. Weak bases like ammonia incompletely dissociate in water and conc. of OH- ions is low.

Question 27

What is Bronsted and Lowry’s theory?

Answer 27

Developed a new theory of acids and bases.
- B/L acid is considered to be a proton donor
- B/L base is considered to be a proton acceptor

Question 28

Explain how the experiment of HCl and ammonia react.

Answer 28

NH3(g) + HCl (g) –> NH4Cl (s)
- Ammonium chloride is a ionic crystal containing NH4+ and Cl- ions.
- The hydrogen chloride molecule has donated a proton to the ammonia molecule to form the ammonia ion. Hydrogen chloride molecule is a Bronsted-Lowry acid and ammonia is a Bronsted-Lowry base. The B/L theory provided explanation about the bases of oxides and carbonates and why not all salts are neutral in water.

Question 29

What is Lewis’s definition?

Answer 29

A Lewis Acid is an electron pair acceptor
A Lewis Base is an electron pair donor.

Question 30

What is the pH range for methyl orange?

Answer 30

3.1-4.4

Question 31

What is the pH range for Bromothymol blue?

Answer 31

6.0-7.6

Question 32

What is the pH range for litmus?

Answer 32

5.5-8.0

Question 33

What is the pH range for phenolphthalein?

Answer 33

8.3-10.0

Question 34

Explain the red cabbage indicator prac?