Chemistry AS Chapter 4 - Acids and Redox

Question 1

Define the term strong acid

Answer 1

An acid that releases all its hydrogen atoms into solution as H+ ions and completely dissociates in aqueous solution

Question 2

Define the term weak acid

Answer 2

An acid that only releases a small proportion of its available hydrogen atoms into solution as H+ ions and only partially dissociates in aqueous solution

Question 3

What is an alkali?

Answer 3

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

Question 4

What happens during the neutralisation of an acid?

Answer 4

H+ ions react with a base to form a salt and water

Question 5

acid + alkali —> ?

Answer 5

salt + water

Question 6

What is a titration and what can they be used for?

Answer 6

A titration is a technique used to accurately measure the volume of one solution that reacts exactly with another solution. They can be used for:
- finding the concentration of a solution
-identification of an unknown chemical
-finding the purity of a substance

Question 7

What is a standard solution?

Answer 7

A solution of known concentration

Question 8

How do you prepare a standard solution?

Answer 8

1. Weigh the solid accurately
2. Dissolve in a beaker using less distilled water than needed to fill the volumetric flask
3. Transfer to the volumetric flask. The last traces of the solution are rinsed into the flask by distilled water
4. Fill the flask carefully to the graduation line by adding distilled water until the bottom of the meniscus lines up with the mark.
5. Slowly invert the flask several times to mix the solution thoroughly, if this step is missed results are unlikely to be consistent

Question 9

What is the acid-base titration procedure?

Answer 9

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 reading to the nearest 0.05cm3
3. Add a few drops of indicator to the solution in the conical flask
4. Run the solution in the burette into the solution in the conical flask, making sure to swirl the flask. The indicator will change colour and this point is used to indicate the volume at which they exactly react
5. Record the final burette reading and this is called the titre
6. A quick trial titration is carried out to figure out an approximate titre
7. The titration is then repeated accurately, adding the solution dropwise near the approximate titre. Stop when two results are concordant (within 0.10 of each other)

Question 10

What is oxidation?

Answer 10

The addition of oxygen
The loss of electrons
An increase in oxidation number

Question 11

What is reduction?

Answer 11

The removal of oxygen
The gain of electrons
A decrease in oxidation number