Chapter 4 (Acids & Redox)

Question 1

What happens to an acid when dissolved in water?

Answer 1

The acid releases its hydrogen ions as protons (H+) into the solution.

Question 2

What makes an acid a Strong Acid?

Answer 2

It releases all its hydrogen atoms into a solution as H+ ions (it completely dissociates)

Question 3

What makes an acid a Weak Acid?

Answer 3

It only releases a small proportion of its available hydrogen atoms into solution as H+ ions (it partially dissociates)

Question 4

What does the equilibrium sign indicate in acid disassociation reactions?

Answer 4

It indicates that the forwards reaction is incomplete

Question 5

What does a base do?

Answer 5

Neutralises an acid to form a salt

Question 6

What are the 4 examples of bases?

Answer 6

Metal oxides,
Metal Hydroxides,
Metal Carbonates,
Ammonia.

Question 7

What is an alkali?
What does it release when dissolved in water?

Answer 7

Its a base that dissolves in water and releases hydroxide ions (OH-) ions into the solution.

Question 8

What are the common bases? (common metal oxides, carbonates and alkalis),(3 of each)

Answer 8

Metal Oxides - MgO, CaO, CuO
Metal Carbonates - Na2CO3, CaCO3, CuCO3
Alkalis - NaOH, KOH, NH3

Question 9

How does the neutralisation of an acid work?

Answer 9

H+ ions react with a base to form a salt + neutral water.
The H+ ions from the acid are replaced by metal or ammonium ions from the base.

Question 10

What is Hydrochloric Acids’ salt?

Answer 10

Sodium Chloride (NaCl)

Question 11

What is Sulfuric Acids’ salt?

Answer 11

Sodium Sulfate (Na2SO4)

Question 12

What is Nitric Acids’ salt?

Answer 12

Calcium Nitrate [Ca(NO3)2]

Question 13

What is Ethanoic Acids’ (vinegar) salt?

Answer 13

Ammonium Ethanoate (CH3COONH4)

Question 14

An Acid is neutralised by a Metal Oxide or a Metal Hydroxide to form what?

Answer 14

a SALT + WATER ONLY

Question 15

An Acid is neutralised by a Metal Carbonate to form what?

Answer 15

a SALT + WATER + CARBON DIOXIDE (g)

Question 16

What is the difference between neutralisation with an ALKALI as opposed to a metal oxide/hydroxide?

Answer 16

The reactants are in solution

Question 17

What is the ionic equation of the following:
HCl(aq) + NaOH(aq) –> NaCl(aq) + H2O(l)

Answer 17

H+(aq) + OH-(aq) –> H2O(l)

Question 18

How is Sulfuric Acid (H2SO4) different from other STRONG Acids?

Answer 18

-It first behaves as a strong acid
-The HSO4(-) formed from its first full dissociation act as a weak acid.
NOTE: Other strong acids with more than one H atom behave similarly.

Question 19

What is a titration?

Answer 19

A titration is a technique used to accurately measure the volume of one solution that reacts exactly with another solution.

Question 20

What can titrations be used for?

Answer 20

• Finding the concentration of a solution
• Identification of unknown chemicals
• Finding the purity of a substance

Question 21

What is a Standard Solution?

Answer 21

A solution of a known concentration

Question 22

How do you prepare a standard solution? (5 steps)

Answer 22

1. Solid is first weighed accurately
2. The solid is dissolved in a beaker with distilled water (water has to be less than what fills the volumetric flask to its mark)
3. Solution transferred to volumetric flask (any last traces rinsed into flask with distilled water)
4. The flask is carefully filled to graduation line with distilled water a drop at a time until bottom of meniscus is exactly on the mark (should be viewed at eye level)
5. Slowly invert flask several times to mix solution.

Question 23

What is the error if the volumetric flask is filled above the graduation line? (titrations)

Answer 23

The concentration of solid will be too little as the solution is too diluted

Question 24

What is the error if the volumetric flask is not inverted? (titrations)

Answer 24

The solid will not be evenly distributed throughout the solution

Question 25

What happens in an Acid-Base titration?

Answer 25

A solution of acid is titrated against a solution of a base using a PIPPETE and a BURETTE

Question 26

What are Burette readings measured to?

Answer 26

The nearest 0.5cm^3

Question 27

What is the Acid-Base titration procedure? (7 steps)

Answer 27

1. Add measured volume of one solution to a conical flask using pipette 2. Add other solution to Burette and record initial burette reading 3. Add a few drops of indicator to solution in conical flask 4. Run solution in burette into solution in conical flask, swirling conical flask throughout until indicator changes colour at the END POINT of the titration 5. Record final burette reading and calculate TITRE (amount of solution added). 6. A quick trial titration is done first to find approximate titre 7. Then titration is repeated accurately until there are 2 concordant titres (titres within 0.10cm^3 of each other)