2.1.4 Acids

Question 1

List the formulas of common acids

Answer 1

HCl
H2SO4
HNO3
CH3COOH

Question 2

List the formulas of common alkalis

Answer 2

NaOH
KOH
NH3

Question 3

Acid

Answer 3

Proton (H+) donor

Releases H+ ions in aqueous solution

Question 4

Alkali

Answer 4

Base that dissolves in water releasing OH- ions in aqueous solution

Question 5

Describe the dissociation of a strong acid

Answer 5

Releases all its H atoms into solution as H+ ions and completely dissociates in aqueous solution

Question 6

Describe the dissociation of a weak acid

Answer 6

Only releases small proportion of its available H atoms into solution as H+ ions, partially dissociates in aqueous solution

Question 7

Base

Answer 7

Proton (H+) acceptor

A base neutralises an acid to form a salt

Question 8

What are classified as bases

Answer 8

Metal oxides
Metal hydroxides
Metal carbonates
Ammonia

Question 9

Salt

Answer 9

Compound formed when H+ of an ion is replaced by a metal or positive ion

Question 10

acid + metal ->

Answer 10

a salt + hydrogen

Question 11

acid + metal oxide ->

Answer 11

a salt + water

Question 12

acid + metal hydroxide ->

Answer 12

a salt + water

Question 13

acid + carbonate ->

Answer 13

a salt + water + carbon dioxide

Question 14

acid + alkali ->

Answer 14

a salt + water

Question 15

Example of a strong acid

Answer 15

HCl

Question 16

Example of weak acid

Answer 16

CH3COOH

Question 17

What is a titration used for

Answer 17

Technique used to accurately measure volume of one solution that reacts exactly with another solution

-Finding conc. of a solution
-Identifying unknown chemicals
-Finding purity of a substance

Question 18

Standard solution

Answer 18

Solution of known concentration

Question 19

Outline how to prepare a standard solution

Answer 19

1. Solid first weighed accurately
2. Solid dissolved in a beaker using less distilled water than required to fill volumetric flask to the mark
3. Solution transferred to a volumetric flask. Last traces of solution are rinsed into the flask with distilled water
4. Flask carefully filled to graduation line with distilled water until the bottom of meniscus lines up exactly with the mark
5. Volumetric flask slowly inverted several times to mix solution

Question 20

Outline the acid-base titration procedure

Answer 20

1. Add a measured volume of one solution to a conical flask
2. Add other solution to a burette. Record initial and final burette reading to nearest 0.05 cm3
3. Add few drops of indicator to solution in conical flask
4. Run solution in burette into the solution in conical flask, swirling the conical flask to mix. Eventually the indicator changes colour at end point of titration
5. Record final burette reading. (volume of solution added from the burette is called the titre)
6. Quick, trial titration is carried out first to find approximate titre
7. Further titrations are carried out until two accurate titres are concordant - agreeing to within 0.10 cm3

Question 21

What is the colour of methyl orange in an acid, base, and at end point

Answer 21

acid: red
base: yellow
end point: orange