Acids And Bases

Question 1

Define acid (Arrhenius theory)

Answer 1

A neutral molecule which dissociates in water to form a hydrogen ion and an anion

Question 2

Define base (Arrhenius theory)

Answer 2

Dissociates in water to form a hydroxide ion and a cation

Question 3

Strong acids and bases(Arrhenius)

Answer 3

Dissociates fully in aqueous solutions

Question 4

Weak acids and bases (Arrhenius)

Answer 4

Only dissociates slightly in aqueous solution

Question 5

Conductivity of weak acids(Arrhenius)

Answer 5

Weak acids conduct poorly because few ions

Question 6

Conductivity of strong acids

Answer 6

Strong acids conduct well because there are numerous ions

Question 7

Limitations of Arrhenius theory

Answer 7

Limited due to dilute aqueous solutions and has been superseded/ amphoteric substance not explained (water not amphoteric)

Question 8

Acid (Bronsted-Lowry theory)

Answer 8

Acid is a proton donor

Question 9

Base ( Bronsted-Lowry theory)

Answer 9

Base is a proton acceptor

Question 10

Strength of acids(Bronsted-Lowry)

Answer 10

Stronger acids more readily donates a proton

Question 11

Conjugate acid-base pairs

Answer 11

Species that differ from each other by H+

Question 12

The strength of an acid if it’s conjugate base is weak

Answer 12

The stronger the acid the weaker the conjugate base

Question 13

Indicator

Answer 13

Substances that changes colour with pH or at the end-point of a titration

Question 14

Define Conjugate acid

Answer 14

Produced by a gain of one h+

Question 15

Amphoteric

Answer 15

It can act as both a Brønsted-Lowry acid and a Bronsted-Lowry based.

Question 16

Neutralisation

Answer 16

the reaction betweem acid and a base to form salt and water.

Question 17

Alkali

Answer 17

a base that is soluble in water.

Question 18

Mono basic acids

Answer 18

Produces one H+ ion in solution

Question 19

Dibasic acids

Answer 19

Produces two H+ ions in solution

Question 20

Tribasic acids

Answer 20

Produces three H+ ions in solution

Question 21

Dissociation

Answer 21

When acids are places in solutions they split up into their ions, hydrogens ions and anions

Question 22

Salts

Answer 22

Formed when the H+ of the acid is replaces by a metal ion

Question 23

Limitation of ph scale

Answer 23

Accurate only for dilute solutions

Question 24

pH

Answer 24

-log10[H+]

Question 25

How to test sample of mineral water for presence of the sulfate ion

Answer 25

Add barium chloride( BaCI2) / white insoluble in HCI remains after addition of HCI when sulfer present

Question 26

Explain the term standardised

Answer 26

Concentration found by another titration

Question 27

State a precaution when end point in sight

Answer 27

Add drop by drop, swirl conical flask and wash down sides of conical flask.

Question 28

Describe how the liquid level in burette was adjusted to zero mark.

Answer 28

Fill above mark and adjust slowly with tap

Question 29

Name a primary standard reagent to standardise the HI solution?

Answer 29

Anhydrous sodium carbonate (Na2COs)

Question 30

Why is sodium carbonate a primary standard yet sodium carbonate crystals are not?

Answer 30

Sodium carbonate is anhydrous where as sodium carbonate crystals are hydrated. Primary standards are anhydrous

Question 31

Why is it necessary to dilute vinegar?

Answer 31

To prevent excess amount of sodium hydroxide being used

Question 32

Purpose of white tile?

Answer 32

To see colour change more clearly.

Question 33

Purpose of swirling conical flask?

Answer 33

To ensure mixing of chemicals

Question 34

What are the two purposes of Sulfuric acid

Answer 34

1. To prevent oxidation of Fe2+ to Fe3+ | 2. To ensure an acidic medium to reduce Mn0+-

Question 35

Why is there never an indicator when potassium permanganate is used?

Answer 35

Potassium permanganate is its own indicator

Question 36

How is iodine brought into aqueous solution?

Answer 36

By reacting iodine with potassium iodide we form potassium triiodide which when dissolved in water simply forms triiodide (soluble).

Question 37

Why is excess potassium iodide used?

Answer 37

Anything "excess" is to ensure all of reactant has reacted/ also to keep iodine in solution.

Question 38

What indicator is used for sodium thiosulfate?

Answer 38

Starch. It is added when pale yellow colour formed. Goes blue-black to colourless

Question 39

Why is distilled water better than deionised water for experiments?

Answer 39

Distilled water contains no chlorine oxidising agents. It is purer than deionised water.

Question 40

Name a primary standard reagent used to standardise potassium permanganate?

Answer 40

Ammonium iron (Il) sulphate.