Acids and Alkalis

Question 1

What does a pH below 7 indicate?

Answer 1

An Acid.

Question 2

What does a pH above 7 indicate?

Answer 2

An Alkali.

Question 3

What does a pH of 7 indicate?

Answer 3

A Neutral solution.

Question 4

What colour will an indicator turn when put into an Acid?

Answer 4

Red/Orange.

Question 5

What colour will an indicator turn when put into an Alkali?

Answer 5

Blue/Purple.

Question 6

What colour will an indicator turn when put into a Neutral Solution?

Answer 6

Green.

Question 7

Why do Acidic Solutions have a pH of less than 7?

Answer 7

They contain more hydrogen ions (H+) than hydroxide ions (OH-)

H+>OH-

Question 8

Can Acids conduct electricity?

Answer 8

Yes, as they contain ions that are free to move.

Question 9

What happens when Acids are dissolved in water?

Answer 9

The concentration of H+ ions decreases, increasing the pH towards 7.

The conductivity of the acid will decrease.

Question 10

What forms acidic solutions?

Answer 10

Soluble Non-Metal Oxides form acidic solutions.

Question 11

Why do alkaline solutions have a pH above 7?

Answer 11

They contain a greater concentration of hydroxide ions (OH-) than Hydrogen ions (H+).

OH->H+

Question 12

Can Alkaline solutions conduct electricity?

Answer 12

Yes, as they have ions that are free to move.

Question 13

What happens when an Alkaline solution is diluted?

Answer 13

The concentration of OH- ions decreases, decreasing the pH towards 7.

The conductivity of will decrease.

Question 14

What forms Alkaline solutions?

Answer 14

Soluble Metal Oxides.

Question 15

Why do Neutral solutions have a pH of 7.

Answer 15

A Neutral solution has an equal concentration of H+ and OH- ions. Therefore they cancel each other out.

Question 16

Water is a reversible reaction. Why is this?

Answer 16

Very small proportions of the water molecules will naturally dissociate to form an equal number of hydrogen and hydroxide ions.

Question 17

What is a Neutralisation Reaction?

Answer 17

Neutralisation is the reaction between acids and a base. This will move the pH of the acid up towards 7 and the base down towards 7.

Question 18

What are three examples of Bases?

Answer 18

Metal Oxides
Metal Hydroxides
Metal Carbonates.

Question 19

Can insoluble Bases still neutralise acids?

Answer 19

Yes, but would not form an alkaline solution.

Question 20

When acids are neutralised, what is formed?

Answer 20

Salt and Water. (And Carbon Dioxide if the base is a Metal Carbonate)

Question 21

What is a Spectator ion?

Answer 21

Spectator ions are ions which are unchanged by a chemical reactions and remain the same on both sides.

Question 22

What are the steps to solving a Spectator Ion question?

Answer 22

1. Word Equation
2. Formula
3. Ionic Formula
4. Removing Spectators.

Question 23

Why would you use an acid/base Titration?

Answer 23

To determine the concentration of an acid/base.

Question 24

What is a Pipette?

Answer 24

A pipette is used to accurately measure the volume of a standard solution.

Question 25

What is a Standard Solution?

Answer 25

A standard solution is a solution of accurately known concentration.

Question 26

What is a Burette?

Answer 26

The burette contains the acid/base of accurately known concentration.

Question 27

Which indicator is used to determine the point of neutralisation?

Answer 27

Phenolphthalein.
Base containing indicator (Pink/Purple) + Acid = Clear

Question 28

Errors of titrations and solutions?

Answer 28

Burette too high/far away from the conical flask (splashes/lost solution) - Bring burette down/closer to conical flask.

Burette too high to read - Bring down to eye level.

Question 29

What is a Concordant Value?

Answer 29

Concordant values need to be within 0.2 cm3 of each other.

Question 30

What is the method of Titration calculations?

Answer 30

1. Establish the molar ratio using the balanced equations.
2. Calculate the number of moles.
3. Use molar ratio.
4. Finish off calculating the concentration.