Acids and Bases

Question 1

What is the pH Scale and what does it show ?

Answer 1

0-6 red to orange to yellow = acids
7 - neutral ( substance like water )
8-14 blue to purples is alkalis

pH scale is a measure of how acidic or alkaline a solution is
Lower pH of a solution = more acidic it is
Higher pH of a solution = more alkaline it is

Question 2

How do you measure pH of a solution ?

Answer 2

Using an indicator that changes colour depending on whether it’s above or below a certain pH. Some indicators contain mixture of dyes that means they gradually change colour over a broad range of a solution. These are called wide range indicator and useful for estimating the pH of a solution.

Question 3

What is attached to a pH meter

Answer 3

a pH probe which can be used to measure pH electronically. The probe is placed in the solution you are measuring and the pH is given on a digital display as a numerical value, meaning it’s more accurate than an indicator.

Question 4

What is an acid, a base ( example ) and what’s the reaction between the two called ?

Answer 4

Acid = substance that forms aqueous solutions with pH less than 7 .
Acids form H + ions in water

An alkali is a base that dissolves in water to form solution with a pH greater than 7. Alkali forms OH^- ions in water.
reaction between acid and base = neutralisation

Question 5

Neutralisation between acid and alkalis can be seen in terms of H+ and OH^- ions

Answer 5

H+ (aq) + OH^- (aq) -> H20 (l)

When an acid neutralises a base ( vice versal ) , the products are neutral i.e. pH of 7
An indicator can be used to show that a neutralisation reaction is over