Chapter 4 - Acids and Redox

Question 1

What is an acid?

Answer 1

Proton donor

Question 2

What is a base?

Answer 2

Proton acceptor

Question 3

What is a strong acid?

Answer 3

Proton donor that completely dissociates in aqueous solution

Question 4

What is a weak acid?

Answer 4

Proton donor that partially dissociates in aqueous solution.

Question 5

What is an alkali?

Answer 5

A base that dissolves in water, releasing hydroxide (OH-) ions into the solution.

Question 6

What is the word equation for neutralisation of acids with metals?

Answer 6

MASH - Metal + Acid —> Salt + Hydrogen

Question 7

What is the word equation for neutralisation of acids with metal oxides?

Answer 7

Metal Oxide + Acid —> Salt + Water

Question 8

What is the word equation for neutralisation of acids with metal hydroxides?

Answer 8

Metal Hydroxide + Acid —> Salt + Water

Question 9

What is the word equation for neutralisation of acids with metal carbonates?

Answer 9

Metal Carbonate + Acid —> Salt + Water + Carbon Dioxide

Question 10

What is the word equation for neutralisation of acids with alkalis?

Answer 10

Acid + Alkali —> Salt + Water

Question 11

What is a titration?

Answer 11

A technique used to accurately measure the volume of one solution that reacts completely with another solution.

Question 12

What are the uses of titrations?

Answer 12

Finding concentration of a solution
Identifying unknown chemicals
Finding the purity of a substance

Question 13

What are concordant results?

Answer 13

Results that are within 0.10cm3 of each other

Question 14

When can a mean titre be calculated?

Answer 14

When 2 or more concordant results are obtained

Question 15

When is the oxidation number zero?

Answer 15

When elements are by themselves or bonded to the same element.

Question 16

What is the oxidation number of Hydrogen?

Answer 16

+1 with non-metals

-1 with metals

Question 17

What is the oxidation number of Oxygen?

Answer 17

always -2

except H2O2 where it is -1

Question 18

What is the oxidation number of group 1 and 2 metals?

Answer 18

Usually +1 and +2

Question 19

What is the oxidation number of halides?

Answer 19

-1 unless bonded with oxygen where it can go positive.

Fluorine is always -1

Question 20

What is oxidation and reduction?

Answer 20

OILRIG - Oxidation is loss of electrons, reduction is gain of electrons

Question 21

What is oxidation and reduction in terms of oxidation number?

Answer 21

Oxidation is increase in oxidation number, reduction is decrease in oxidation number

Question 22

How to make a standard solution?

Answer 22

1. Weigh solid using mass balance and dissolve in beaker. Use less distilled water than what would fill up to the mark of a volumetric flask.
2. Transfer solution to volumetric flask. Rinse the last traces of solution into the flask using distilled water.
3. Fill the flask up to the graduation line one drop at a time until the bottom of the meniscus lines up with the mark. View the flask from eye level for accuracy.
4. Slowly invert the volumetric flask to mix the solution.

Question 23

Why does the bottom of the meniscus have to line up with the mark?

Answer 23

If it is above the mark, then the solution will be too diluted and won’t be the correct concentration.

Question 24

Why is the flask inverted?

Answer 24

To mix the solution so that the concentration is consistent throughout the solution. This stops us from getting incorrect titration results.

Question 25

What is the method for a titration experiment?

Answer 25

1. Using a pipette, add a measured volume of one solution to the conical flask and put a few drops of indicator in it.
2. Add the other solution to the burette and record the initial burette reading to the nearest 0.05cm3.
3. Slowly add the solution in the burette to the solution in the conical flask and swirl continuously.
4. Stop swirling and close the burette when the end point is reached. Record the new reading on the burette.
5. A trial is carried out to find the approximate titre.
6. Repeat the titration until concordant results within 0.10cm3 of each other are obtained.

Question 26

What does the end point indicate?

Answer 26

The volume of one solution that exactly reacts with the volume of the second solution.

Question 27

What is the word equation for a reaction between a metal and water?

Answer 27

Metal + Water —> Metal Hydroxide + Hydrogen

Question 28

How do we remove air bubbles from the burette prior to experiment?

Answer 28

Run the solution out through the tap until all air bubbles are removed.

Question 29

What does the end point indicate?

Answer 29

The volume of one solution that exactly reacts with the volume of the second solution.