Chapter 4

Question 1

What is meant by the term salt?

Answer 1

When the H+ in an acid is replaced by a metal ion

Question 2

What action is considered ‘acting as a base’ during neutralisation?

Answer 2

Accepting a proton

Question 3

What term is given to the ‘xH20’ part of a hydration of salt formula?

Answer 3

Water of crystallisation

Question 4

Hydrogen oxidation number special cases:

Answer 4

-1 instead of +1 in metal hydrides such as NaH or CaH2

Question 5

Oxygen oxidation number special cases:

Answer 5

-1 instead of -2 in peroxides such as H2O2

+2 instead of -2 when bonded to a flouride ion

Question 6

What do you see when magnesium reacts with excess sulfuric acid?

Answer 6

Effervescence, and the magnesium solid dissolves

Question 7

Strong vs weak acid

Answer 7

Strong acid fully dissociates from its H+ ions in solution
Weak acid partially dissociates from its H+ ions in solution

Question 8

Why are titrations done?

Answer 8

Accurately measures the volume of one solution that reacts exactly with another solution

Question 9

Standard solution

Answer 9

Solution of known concentration

Question 10

Preparing a standard solution method

Answer 10

1. The solid is weighed accurately.
2. The solid is dissolved in a beaker using less distilled water than will be needed to fill the volumetric flask to the mark.
   3.
   The solution is transferred to a volumetric flask, and the last traces of solution are rinsed out of the beaker and into the flask with distilled water.
3. The flask is filled by adding distilled water drop by drop until the bottom of the meniscus lines up exactly with the graduation line. View the meniscus and graduation mark at eye level for accuracy.
   5.
   Slowly invert the volumetric flask several times.

Question 11

What happens when sulfuric acid, H2SO4, (a strong acid) is mixed with water?

Answer 11

Sulfuric acid is a strong acid, but only one of its H atoms behaves this way
Only 1 H atom will be released upon mixing with water
Forming H+ and HSO4-
Which then behaves like a weak acid
All other strong acids with multiple hydrogens do this

Question 12

Preparing a standard solution errors

Answer 12

Don’t fill the flask with water above the graduation line or the solution will be too dilute and must be prepared again.

Dont forget to invert the flask several times to mix thoroughly or the titration results will not be consistent

Question 13

The acid-base titration procedure

Answer 13

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 0.05 cm3.
3. Add a few drops of an indicator 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 indicator changes colour at the end point of the titration. The end point is used to indicate the volume of one solution that exactly reacts with the volume of the second solution.
5. Record the final burette reading. The volume of solution added from the burette is called the titre, which is calculated by subtracting the initial from the final burette reading.
6. A quick, trial titration is carried out first to find the approximate titre.
7. The titration is then repeated accurately, adding the solution dropwise as the end point is approached. Further titrations are carried out until two accurate titres are concordant — agreeing to within 0.10 cm3.

Question 14

Explain what is meant by the term salt (1)

Answer 14

When the H+ in an acid is replaced by a metal ion