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Flashcards in Titrations - Acids and Bases Deck (42):
1

What is a titration?

It is a laboratory procedure where a measured volume of one solution is added to a known volume of another solution until the reaction is complete

2

What is a primary standard?

It’s a water soluble substance that is stand and available in pure form. It can be used to make a solution of known concentration

3

What is a molar solution?

It’s a solution that contains 1 mole of a solute dissolved in 1 litre of solution

4

What is a standard solution?

It’s a solution whose concentration is accurately known

5

How to prepare a primary standard -
Why is a volumetric flask used?

When it is filled to the calibration mark at the temperature stated on the flask, it contains a specific known volume therefore is more accurate

6

How to prepare a primary standard -
What primary standard is used?

Anhydrous sodium carbonate

7

How to prepare a primary standard -
What is used to measure mass of solute and ensure it’s accurate?

Analytical balance

8

How to prepare a primary standard -
What is the purpose of the wash bottle?

Ensure no solution is lost when transferring

9

How to prepare a primary standard -
How do you ensure solution is homogenous?

Stopper flask and invert it several times

10

How to prepare a primary standard -
Purpose of narrow neck of volumetric flask?

It is necessary to read meniscus

11

Describe the procedure to prepare a primary standard solution of sodium carbonate

-weigh the solute accurately using analytical balance
-transfer sodium carbonate to deionised water [wash bottle]
-stirring rod to mix and dissolve all of sodium carbonate in water
-using funnel, pour into volumetric flask [filled to calibration mark, specific known volume]
-rinse beaker and add rinsings to flask
-carefully being bottom of mensicus up to graduation mark on volumetric flask
-stopper flask and invert several times to ensure homogenous solution

12

How to prepare a primary standard -
Why is anhydrous sodium carbonate used?

Available in pure form
Stable
Water soluble

13

What is a homogenous solution?

An evenly mixed solution

14

What's the objective of standardisation?

To find it’s concentration accurately

15

Why can’t standard solutions be made directly?

They are not readily available in pure form

16

Standardisation of a hydrochloric acid solution using a standard solution of sodium carbonate -
What indicator solution is used and what’s the colour change?

Methyl orange indicator solution
Yellow - peach/pink

17

Precautions to ensure accurate titration results

-burette is washed out with pure water and then solution it is to contain
-solution added using beaker and funnel
-tap of burette is opened briefly to fill the part of the burette below the tap [displaces air]
-burette filled up until the label of the liquid is above the 0cm3 mark
-tap is opened of burette to ensure its at definite mark
-burette readings taken at eye level : bottom of meniscus read
-pipettes washed with pure water and then solution to be contained [conical with only water]
-indicator either weak acids or weak bases adding too much with affect accuracy
-white tile
-conical flask swirled and any solution on sides can be washed down using water bottle
-rough titrations
-mean of titres is result

18

Why is a burette more accurate than a graduated cylinder

Markings are easier to read

19

Burette -
Why is the funnel removed before adjusting the burette to zero?

Ensure no drops fall into the burette which would give an inaccurate reading

20

Burette -
Why must the burette be vertical?

Allow the meniscus to be properly lined up with graduation mark

21

Burette -
Why is it rinsed first with deionised water and then solution to contain?

Deionised water - remove impurities
Solution to contain - removes remaining drops of water which may dilute solution

22

Burette -
Why is the tap opened?

The tip must be full too as the graduation on the burette includes this space and therefore rid of air bubbles present - which would yield false results

23

Safety precautions when filling burette

- Remove funnel before adjusting to zero so no drops fall into burette
- Vertical to ensure the mensicus is properly in line with graduation mark
-rinse first with deionised water [remove impurities] solution to contain [remove remaining drops of water which may dilute solution]
-read meniscus at eye level
-tip must be full as the graduation on burette includes this space

24

What precautions should be taken when filling the pipette?

-always use pipette filler
-rinse with deionised water [remove impurities] and solution it is to contain [removes remaining drops of water which may dilute solution]
-read mensicus at eye level

25

Wat precautions should be taken when delivering from pipette?

Hold pipette vertically
Touch tip of pipette against inside of conical flask to release last drop.

26

Why is the conical flask used in these experiments?

Shaped to prevent spillage when being swirled

27

Why is conical flask only rinsed with deionised water?

It should not be rinsed with solution it is to contain because the remaining drops will mean he total volume in the flask will be unknown

28

During the titration, why are the sides of the flask washed down?

Ensure all the liquid from burette reacts in conical flask

29

Give one reason why a volumetric flask is preferable to a graduated cylinder

It’s a more accurate piece of equipment -
Narrow neck on flask and also when it is filled to the calibration mark, with temperature shown, there is a specific known volume

30

Give one reason why a conical flask is preferable to a beaker

It’s easier to mix solutions due to shape - wide base, avoids spillages

31

During the titrations, drops of the hydrochloric acid were noticed on the sides of the conical flask. What action would you take to deal with this problem? Why is it possible to take this action without affecting the result of the titration?

Wash down with deionised/distilled water
Water does not affect the amounts of either reactant because they were both measured before they entered the flask by the pipette and burette

32

In volumetric analysis, what is the advantage in carrying out a rough titration?

It gives an indication of the required volumes of both reagents needed for neutralisation, further titrations can be carried out much more quickly when the expected point is known

33

Hydrochloric acid/sodium hydroxide titration and the use of this titration in making the salt sodium chloride -
What is the purpose of the HCL

HCL has been standardised - know concentration. it is used to find concentration of sodium hydroxide

34

Hydrochloric acid/sodium hydroxide titration and the use of this titration in making the salt sodium chloride -
To obtain a sample of salt

-place 25cm3 of the sodium hydroxide solution in a beaker with no indicator
-using results from earlier, add enough hydrochloric acid to neutralise it
-gently hear solution until all water has been evaporated. Sample of sodium chloride will remain

35

Determining the concentration of ethanoic acid in vinegar -
What indicator is used and what is the colour change?

Phenolphthalein indicator
Pink to colourless

36

Determining the concentration of ethanoic acid in vinegar -
Why is the vinegar diluted?

To avoid as very small titre which would reduce the accuracy of the experiment

37

Determining the concentration of ethanoic acid in vinegar -
How would you dilute the vinegar?

-place 25cm2 of vinegar in a 250cm2 volumetric flask and dilute with water up until calibration mark
-stopper and invert several times - homogenous solution

38

Procedure of a titration

-rinse burette, puppets and conical flask
-fill pipette - base and add to conical flask
-add indicator to conical flask
-fill burette with acid to the 0cm3 mark, open tap
-rough titration, three accurate titrations
-calculate

39

How do you calculate the concentration of ethanoic acid in diluted vinegar solution?

-formula
-multiply by 10
-find grams
-divide by 10

40

Determination of the amount of water of crystallisation in hydrated sodium carbonate -
What indicator is used and what is the colour change?

Methyl orange
Yellow to peach/pink

41

Determination of the amount of water of crystallisation in hydrated sodium carbonate -
How do you make up sodium carbonate solution?

SAME AS PRIMARY STANDARD
-weight solute of hydrated sodium carbonate accurately
-add to beaker of deionised water and wash down
-transfer with funnel into volumetric flask ad add water to the graduation mark
-stopper and invert

42

How do you determine the formula of hydrated sodium carbonate?

GRAMS PER LITRE