38. Principle of concentration determination by volume measurement: titrations

Question 1

pH formula

Answer 1

pH = - log [H+]

Question 2

The concentration of acids and bases can be determined by _____ reaction

Answer 2

neutralization

Question 3

What is the principle of titrations

Answer 3

to add a strong base of known concentration (titrating solution) to an acid of unknown concentration
=> to reach the equivalency of hydroxonium and hydroxyl ions.

Question 4

What happen at the end of titration?

Answer 4

Hydrogen ions (H+) coming from the dissociation of the acid react completely with hydroxide ions (OH-) coming from the base

Question 5

What happen to pH of solution in which strong acids are titrated?

Answer 5

If strong acids are titrated, a neutral solution (pH = 7) is obtained

Question 6

What happen at at the end of the titration in which strong bases are titrated?

Answer 6

At the end of the titration, hydroxide ions of the base solution react completely with protons of the titrating acid solution.
=> a neutral pH (pH = 7) will be also obtained.

Question 7

When titrating basic solution, which acids or bases that are used?

Answer 7

a strong acid of exactly known concentration must be added to a solution of a base of unknown concentration if alkaline solutions are titrated

Question 8

What are general equation of acid-base titration in aqueous solution?

Answer 8

HA → A-+H+ (acid)

BOH → B+ + OH- (base)

H+ + OH- → H2O

pH=-log[H+]

pOH = - log [OH-]

Question 9

How To detect the end point of the reactions?

Answer 9

various pH indicators are used

Question 10

Which solution is most frequently used for the titration of bases?

Answer 10

Strong acids such as HCl

Question 11

Which types of concentrations are used to prepare for the titration of strong bases? Give an example

Answer 11

1N, 0.1 N or 0.01 N HCl (strong acids)

Question 12

Which solution is most frequently used for the titration of acids?

Answer 12

strong bases, generally NaOH is used

Question 13

Which types of concentrations are used to prepare for the titration of strong acids? Give an example

Answer 13

1 N, 0.1 N or 0.01 N NaOH (strong bases)

Question 14

Explain titration procedure with HCl (unknown concentration)

Answer 14

• The burette is filled with a titrating solution of known concentration (e.g. 0.1 N).
• A certain volume of the HCl solution is taken into a flask and acid-base indicator sensitive to pH changes is added.
• Titrating NaOH solution is mixed slowly to the flask until the color change of the indicator shows the the equivalence point (end point)