4. ACIDS AND REDOX

Question 1

Define Strong acid

Answer 1

An acid that dissociates completely in solution

Question 2

Define Weak acid

Answer 2

An acid that partially dissociates in solution

Question 3

Define Base

Answer 3

A compound that neutralises an acid to form a salt

Question 4

Give examples of strong acids

Answer 4

HCl - hydrochloric acid
H2SO4 - sulfuric acid
HNO3 - nitric acid

Question 5

Give an example of a weak acid

Answer 5

CH3COOH - ethanol acid

Question 6

How can you tell if an acid is weak from the equation?

Answer 6

There will be an equilibrium sign which indicates that the forward reaction is incomplete

Question 7

What type of compounds are bases? give examples

Answer 7

Metal oxides - MgO, CaO, CuO
Metal hydroxides - NaOH, KOH
Metal carbonates - Na2CO3
Ammonia - NH3

Question 8

Give examples of alkalis

Answer 8

NaOH
KOH
NH3

Question 9

Metal + Oxide —>

Answer 9

Salt + Water

Question 10

Acid + Metal hydroxide —>

Answer 10

Salt + Water

Question 11

Acid + Alkali —>

Answer 11

Salt + Water

Question 12

Acid + Carbonate —>

Answer 12

Salt + Water + Carbon dioxide

Question 13

Give me step by step how to prepare a standard solution

Answer 13

1. Accurately weigh the solids (using a digital scale)
2. Dissolve the solid in the beaker using distilled water
3. Transfer the solution to a volumetric flask and rinse the last traces of the solution into the flask with distilled water
4. Carefully fill the flask to the graduation line using distilled water. Do this a drop at a time until the bottom of the minis us lines up with the graduation line. View this at eye level for accuracy
5. Invert the volumetric flask several times to mix the solution thoroughly.
   -> If this step is omitted titration results are unlikely to be consistent

Question 14

Give me step by step how to perform a titration

Answer 14

1. Add a measured volume of one solution to a conical flask using a pipette
2. Add the other solution to a burette, and record the initial burette reading to the nearest 0.05cm^3
3. Add a few drops of an indicators to the solution in the conical flask
4. Run the solution in the burette into the solution in the conical flask, swirling the conical flask throughout to mix the two solutions.
   Eventually the solution changes colour at the end point of the titration.
5. Record the final burette reading
   Initial reading - final reading = titre

• A quick trial titration is carried out first to find the approximate titre
  -> The titration is then repeated accurately, adding the solution drop-wise as the end point is approached
• Further titrations are carried out until two accurate titres are concordant (within 0.10cm^3)

Question 15

What does the end point of a titration indicate?

Answer 15

The volume of one solution that exactly reacts with the other solution

Question 16

What do you do with your titration results?

Answer 16

From the titration you know the concentration and volume of the standard solution and the volume of the other solution.

Use n = cv to find the moles of the standard solution

The use the equation and ratio to find the moles of the other solution

Use c = n/V to find the concentration of the other solution

Question 17

What is the oxidation number of single elements?

Answer 17

0

Question 18

What is the oxidation number of H in metal hydrides (e.g NaH)?

Answer 18

-1

Question 19

What is the oxidation number of O in peroxides (e.g. H2O2)?

Answer 19

-1

Question 20

What is the oxidation number of O bonded to F?

Answer 20

+2

Question 21

What are redox reactions?

Answer 21

Reactions that involve reduction and oxidation

Question 22

What is reduction

Answer 22

gain of electrons

Question 23

What is oxidation?

Answer 23

loss of electrons