Chemical Changes: Acids and Bases

Question 1

The lower the pH the more _______.

Answer 1

acidic

Question 2

The higher the pH the more _________.

Answer 2

alkaline

Question 3

What pH will a neutral substance have? What is an example of a substance which is neutral?

Answer 3

A neutral substance has a pH of 7.
e.g. pure water

Question 4

What is a base?

Answer 4

• has a pH above 7
• reacts with an acid to form a salt

Question 5

What is an acid?

Answer 5

• forms H⁺ ions in water
• has a pH of less than 7

Question 6

What is an alkali?

Answer 6

• a type of base that is soluble in water
• this forms a solution with a pH greater than 7
• forms ^-OH ions in water

Question 7

What is the reaction for neutralisation?

Answer 7

acid + base → salt +water

Question 8

What is the ionic equation for neutralisation?

Answer 8

H⁺_(aq) + ^-OH_(aq) → H₂O_(l)

Question 9

What is the pH scale?

Answer 9

The measure of acidity/alkalinity of a solution.

Question 10

What is a strong acid and a weak acid ?

Answer 10

A strong acids completely dissociate in solution whereas weak acids do not fully dissociate in solution.

Question 11

What happens to pH as the concentration of H⁺ increases?

Answer 11

the pH decreases

Question 12

What is a concentrated acid and what is a dilute acid?

Answer 12

Concentrated acids have more moles of acid per unit volume than dilute

Question 13

How is a concentrated acid different to a strong acid?

Answer 13

Strength refers to whether the acid is completely ionised/dissociated in water or partially.
Concentrated acid refers to having more moles of acid per unit volume.

Question 14

As the pH is decreased by one unit, what change is seen in the hydrogen concentration?

Answer 14

Increases by a factor of 10

Question 15

Name the following salts: LiNO₃, K₂CO₃, MgBr₂, BaSO₄.

Answer 15

• lithium nitrate
• potassium carbonate
• magnesium bromide
• barium sulfate

Question 16

What happens to the proportion of H⁺ as pH increases by 1?

Answer 16

proportion of H⁺ decreases by 10x

Question 17

Is the ionisation of a strong or weak acid reversible?

Answer 17

weak