PAG 11 - pH Measurement

Question 1

3 ways to identify if solution acidic/basic

Answer 1

Litmus paper

Indicator (e.g. universal indicator) and comparison to colour scale

pH meter

Question 2

Litmus paper to identify alkali

Answer 2

Red litmus paper turns blue

Blue litmus paper remains blue

Question 3

Litmus paper used to identify an acid

Answer 3

Blue litmus paper turns red

Red litmus paper remains red

Question 4

Why use pH meter rather than universal indicator to measure pH

Answer 4

Gives numerical value for pH

More accurate (read 2dp)

Question 5

What’s meant by accuracy

Answer 5

How close measurement is to true value

Question 6

What equation link pH and H+

Answer 6

pH = -log[H+]

[H+] = 10^-pH

Question 7

Outline how to do titration

Answer 7

1. Use a pipette to measure the first solution into a conical
   flask
2. Add a few drops of a suitable indicator
3. Add the other solution into a burette and record the initial
   volume
4. Slowly add the solution in the burette into the conical flask
5. Swirl the mixture continuously until the end point is reached
6. Repeat until concordant results are obtained

Question 8

What colour is methyl orange in:
A) acid
B) alkali
C) neutral solution

Answer 8

A) red

B) yellow

C) orange

Question 9

What is colour of phenolphthalein in:
A) acid
B) alkali

Answer 9

A) colourless

B) pink

Question 10

Define bronsted Lowry acid

Answer 10

Proton donor

Question 11

Define bronsted Lowry base

Answer 11

Proton acceptor

Question 12

What’s the diff between strong and weak acid

Answer 12

Strong = completely dissociates

Weak = partially dissociates

Question 13

Solution has pH of 1.00 when measured using a pH meter

Suggest characteristics of this solution

Answer 13

Acidic

Likely to contain strong acid