Acids and alkali

Question 1

What is the pH scale?

Answer 1

It is a measure of how acidic or alkaline a substance is.
pH 7 is neutral
The higher concentration of hydrogen ions the more acidic
The lower concentration of hydrogen ions the less acidic/more alkaline

Question 2

What is a base?

Answer 2

Is a substance that reacts with an acid to produce a salt and water.

An alkali is a base that is soluble in water.
All alkalis have a pH more than 7 and they form OH- ions
So the more concentrated OH - ions the more the higher pH

Question 3

How do you measure the pH of a solution?

Answer 3

Use an indicator that changes colour when it’s below or above a pH. This is called a universal indicator.

Question 4

What colour does litmus turn in acidic and alkaline solutions? And also when neutral?

Answer 4

Red in acidic
Purple in neutral
Blue in alkaline

Question 5

What colour does methyl orange turn in acidic and alkaline solutions? And also when neutral?

Answer 5

Red in acidic
Yellow in neutral
Yellow in alkaline

Question 6

What colour does phenolphathalein turn in acidic and alkaline solutions? And also when neutral?

Answer 6

Colourless in acidic
Colourless in neutral
Pink in alkaline

Question 7

How do acids and bases neutralise each other?

Answer 7

Acid + base = salt + water
Eg
HCl + NaOH = NaCl + H2O