Acids and Alkalis

Question 1

How can you detect whether a substance is a strong acid or a strong alkali using a universal indicator?

Answer 1

Red - strong acid
Yellow- Weak acid

Green neutral

Light blue - weak alkali
Blue/purple - Strong alkali

Question 2

How is water formed in a reaction between an acid and an alkali?

Answer 2

H+ Ions from acid react with OH- ions from alkali

Question 3

How can you measure pH

Answer 3

Using a universal indicator

Question 4

What happens if you react an acid and a base together?

Answer 4

A neutralisation reaction which produces salt and water

Question 5

What are some examples of acids and bases?

Answer 5

Hydrochloric acid
Sulfuric acid
Nitric acid

Bases:t

Sodium hydroxide
Calcium carbonate

Question 6

why does mixing an acid and an alkali create a neutral substance?

Answer 6

Acids form hydrogen (H+) ions when they dissolve in water.
Alkalis form hydroxide (OH-) ions when they dissolve in water.
H+ and OH- ions combine to form H2O, otherwise known as water!
Water is a neutral substance so an acid and an alkali neutralise each other.

Question 7

what is the difference between strong and weak acids?

Answer 7

A strong acid ionises completely in water
A weak acid partially ionises in water

Question 8

Each time the pH increases by 1, how much does the concentration of hydrogen ions change by?

Answer 8

For an increase in pH, the solution is less acidic so the concentration of hydrogen ions gets 10x lower.

For a decrease in pH, the solution is more acidic, so the concentration of hydrogen ions gets 10x higher

Question 9

What is a titration?

Answer 9

• How much acid is used to neutralise a base
• the vertical point shows where the solution is neutral and is the end point of titration
• When an acid is added to a base. the pH decreases.
• When a base is added to an acid , the pH increases