C4: Chemical Changes

Question 1

What does pH measure?

Answer 1

How acidic or alkali a substance is.

Question 2

What is the pH for acidic solutions?

Answer 2

1-6

Question 3

What is the pH for alkaline solutions?

Answer 3

9-14

Question 4

What is an indicator?

Answer 4

A dye that changes colour depending on it’s pH.

Question 5

What happens when acids and bases react with each other?

Answer 5

Neutralization

Question 6

How do you carry out titration?

Answer 6

1. Use the pipette and pipette filler to add 25 cm3 of alkali to a clean conical flask.
2. Add a few drops of indicator and put the conical flask on a white tile.
3. Fill the burette with acid and note the starting volume.
4. Slowly add the acid from the burette to the alkali in the conical flask, swirling to mix.
5. Stop adding the acid when the
   end-point
   is reached (when the indicator first permanently changes colour). Note the final volume reading.
6. Repeat steps 1 to 5 until you get
   concordant titres
   (see step 1 in the Analysis). More accurate results are obtained if acid is added drop by drop near to the end-point.

Question 7

What colour is litmus if an acid is present?

Answer 7

Red

Question 8

What colour is litmus if an alkali is present?

Answer 8

Blue

Question 9

What colour is phenolphthalein if an acid is present?

Answer 9

Colourless

Question 10

What colour is phenolphthalein if an alkali is present?

Answer 10

Pink

Question 11

What colour is methyl if an acid is present?

Answer 11

Red

Question 12

What colour is methyl if an alkali is present?

Answer 12

Yellow

Question 13

Why would you use a single indicator in titrition?

Answer 13

It is a clear colour change

Question 14

What do acids produce when in water?

Answer 14

Protons

Question 15

What ions do acids produce in aqueious solutions?

Answer 15

Hydrogen ions. H+