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Question 1

what is a pipette used for?

Answer 1

It is used to deliver a precise quantity of liquid

Question 2

what precautions should be taken when using a pipette?

Answer 2

The pipette should be rinsed with deionised water followed by the solution that will go into it before use.
A pipette filler should be used
Readings should be taken from the bottom of the miniscus(execpt KMnO4).
Don’t blow out the last drop
Pipette should be touched againt the side of the conicalo flask.

Question 3

What is a graduated cylinder used for?

Answer 3

Used to deliver the approximate quantity of a liquid

Question 4

What precautions should be taken when using a graduated cylinder

Answer 4

Readings should be taken from the bottom of the miniscus

Question 5

What is a Burette used for?

Answer 5

used for caring out a titration and delivering an exact volume of liquid

Question 6

What precautions should be taken when using a Burette?

Answer 6

It should be washed with deionised water followed by the solution it is going to contain.
It should be clamped vertically
A little bit of solution should be let run through the tap before the experiment starts to ensure accurate titration reading(Also ensures the volume below the tap is full of chemical)
Readings taken from the bottom of the miniscus exxept for KMnO4

Question 7

What is the Conical Flask used for?

Answer 7

Used for carrying out a reation in

Question 8

What precautions should be taken when using a conical flask

Answer 8

Should be washed out with deionised water only
The conical flask should be swirled during the titration
The sides should be washed down deionised water in a wash bottle to ensure accurate results.
Awhite tile should be placed under the conical flask so the colour change is clear

Question 9

What is a Volumetric flask used for?

Answer 9

Used to make up standard solutions

Question 10

What precautions should be taken when using a volumetric flask

Answer 10

Conical flask should be washed out with deionised water only.
When making up the solution, the final volume of water should be added with a dropper
The flask should be stoppered and inverted 20 times to mix it thoroughly.
Some solutions should be poured into a clean beaker and pipetted from the beaker, rather than from the volumetric flask directly.

Question 11

What is a primary standard?

Answer 11

A substance that can be weighed out precisly and used to make up a standard solution.
1.easy to weigh out
2.Available pure
3.Dissloves well in water
4.Does not react with oxygen or water vapour in air

Question 12

What is a standard solution?

Answer 12

whose concentration is known exactly

Question 13

Name the two primary standards on the course?

Answer 13

Ammonium Iron(II) Sulphate (oxidation and reduction)
Anyhdrous sodium carbonate (acid base titration)

Question 14

what is hydrolysis?

Answer 14

reaction involving water

Question 15

What must be done before ammounium iron (II) sulphate (oxidation/reduction titrations) can be used as a primary standard?
why?

Answer 15

It must be acidified using dilute sulphuric acid
In order to stop the iron from being prematurely oxidised by oxygem in the air or dissolved in water

Question 16

Strong base and strong acid indicator?

Answer 16

Methyl orange

Question 17

Strong acid and weak base titrations?

Answer 17

Methyl orange

Question 18

strong base and weak acid titrations?

Answer 18

Phenolpthalein

Question 19

What colour is Methyl orange in a base?

Answer 19

Yellow

Question 20

What colour is Methyl orange in an acid?

Answer 20

Red

Question 21

What colour is phenolpthalein in a Base?

Answer 21

Pink/purple

Question 22

What colour is phenolpthalein in an Acid?

Answer 22

COLOURLESS!

Question 23

2012 Describe how the student should prepare 500cm3 of the 0.05M Primary standard solution from a known mass of pure anhydrous sodium carbonate, suplied on a clock glass?

Answer 23

Using a wash bottle of deionised water the anhydrous sodium carbonate is
washed from the clock glass into a clean beaker. The clock glass is then washed
repeatedly into the beaker again using deionised water in a wash bottle. The
contents of the beaker are stirred with a glass stirring rod. The contents of the
beaker are transferred to a 500cm3 clean volumetric flask using a funnel. The
beaker and the stirring rod are washed into the volumetric flask using the wash
bottle of deionised water. The solution is made up to the mark on the neck using
a dropper, so that the bottom of the meniscus is sitting on the mark. The flask is stoppered and inverted 20 times

Question 24

2012
Describe how the liquid level was adjusted to the zero mark

Answer 24

The solution is allowed to run through the tap to waste until the bottom of the miniscus is sitting on the mark

Question 25

2012 why was the pipette filler used to fill the pipette with 25.0cm3 solution of the sodium carbonate solution?

Answer 25

a pipette filler is used for saftey reasons so the base, sodium carbonate doesn't get in your mouth

Question 26

2012 Name a suitable indicator for this titration State the colour change observed at the end point

Answer 26

Methyl orange Yellow to red colour change.

Question 27

Describe how the student should have prepared 500 cm of the 0.05 M primary standard solution from a known mass of pure anhydrous sodiun carbonate, supplied on a clock glass.

Question 28

2014 Describe in detail how the chemist should have dissolved the weighed sample of washing soda crystals and made the solution up to exactly 250 cm

Answer 28

The crystals would have been poured from the clock glass into a clean beaker with 100cm3 of deionised water. The solution is stirred with a glass rod. The clock glass is rinsed into the beaker with a wash bottle of deionised water. The solution is poured into a 250cm3 volumetric flask through a funnel. The solution is made up to mark so

Question 29

2014 State one precaution that should have been taken as the end point of the titration was approached. Explain how this precaution would have contributed to the accuracy of the titration result.

Answer 29

the bottom of the meniscus is sitting on the mark using a dropper of deionised water. The conical flask should have been swirled and the sides of the conical flask should be rinsed down with a little of deionised water from a wash bottle, this ensures that the chemicals have a chance to react fully.

Question 30

2014 Name a suitable indicator for this titration. State the colour change in the titration flask at the end point.

Answer 30

The indicator is methyl orange, the colour change is yellow to red.

Question 31

2006) Identify a primary standard reagent that could have been used to standardise the hydrochloric acid solution.

Answer 31

Sodium carbonate

Question 32

2006) Name a suitable indicator for the tiration and state the colour change observed in the conical flask at the end point. Explain why not more than 1 -2 drops of indicator should be used.

Answer 32

Methyl Orange, colour change from yellow to red, Only 1 or 2 drops are used as methyl orange is a weak acid and this could effect the titration result if too much were used.

Question 33

(ii) Describe the correct procedure for rinsing the burette before filling it with the solution. (ii) Why is it important to fi1l the part below the tap of the burette?

Answer 33

The Burette should be rinsed with deionised water, some deionised water should be let run through the tap to waste. The burette is calibrated to include the volume below the tap therefore it has to be filled in order to get an accurate result.

Question 34

2017) Give two essential properties of a primary standard for volumetric analysis.

Answer 34

A standard solution is one whose concentration is known exactly. Two essential properties are that the substance is available pure and is easy to weigh out ( has a high molecular mass).

Question 35

2017 Explain why it was necessary i)to use dilute sulfuric acid when preparing the standard solution from hydrated ammonium iron(|I) sulfate, i)to add more dilute sulfuric acid to each 25.0 cm portion of the standard solution used in the titrations.

Answer 35

The sulphuric acid protects the Fe? from early oxidation to Fe by oxygen in the air or oxygen dissolved in the water. It also stops hydrolysis. More sulphuric acid is added to ensure that the potassium permanganate can work at full oxidising power, i.e. be fully reduced. [+7 to +2 rather than +7 to +4)

Question 36

2017 ) Describe fully the procedure used during the titrations to ensure the accuracy of the end point. What observation indicates that the correct end point has been reached?

Answer 36

The conical flask is constantly swirled and the sides of the flask are washed down with a wash bottle of deionised water. The conical flask is placed on a white tile to ensure the colour change can be seen more clearly. The burette is read from the top-of the meniscus ( for KMnOa it is the top ) The end point is reached when one drop of potassium permanganate from the burette causes the liquid in the conical flask to change from colourless to pink.

Question 37

2003) Why was it important to use dilute sulfuric acid as well as deionised water in making up the solution from the tablets?

Answer 37

a) The tablets won't dissolve in deionised water alone, also stops premature oxidation of the iron from Fe2- to Fe2+

Question 38

2003) Describe in detail the procedure for making up the 250 cm solution from the tablets.

Answer 38

(b) The crushed iron tablets were transferred to a beaker that contains 100cm³ of deionised water. A wash bottle of deionised water was used to wash the mortar and pestle into the beaker. A glass stirring rod was used to help the iron tablets dissolve. The contents of the beaker were transferred to a 250cm² volumetric flask that had previously been washed out with deionised water, a funnel was used. The beaker and glass stirring rod were washed into the volumetric flask with deionised water. A dropper of deionised water was used to make up to the mark; the flask was stoppered and inverted 20 times.

Question 39

2003)Why was more dilute sulfunc acid added before the titrations were commenced

Answer 39

More sulphuric acid is added to ensure that there is an excess of H*so the potassium permanganate can work at full oxidising power. i.e. need to go from Mn (+7) to Mn (+2), don't want MnOz ( Mn (+4)) formed.

Question 40

2011) Describe how the 25.0 cm sample of the original bleach solution was diluted to exactly 500 cm

Answer 40

Using a pipette that had been rinsed with deionised water followed by bleach, the 25cm3 pipette was filled with bleach up to the mark using a pipette filler. The bleach was then allowed to drain into a clean beaker, the last drop was not 'blown out'. Some (100 cm3) deionised water was added. The contents of the beaker were transferred to a volumetric flask that had previously been washed out with deionised water, a funnel was used. The beaker was washed into the volumetric flask with deionised water. A dropper of deionised water was used to make up to the mark, the flask was stoppered and inverted 20 times.

Question 41

(2011) What colour developed when the potassium iodide and the sulfuric acid reacted with the diluted bleach in the conical flask? Give twvo reasons why excess potassium iodide was used.

Answer 41

Red / brown colour (due to l, being liberated.) Excess KI was added to ensure there was enough I ions for the active ingredient ( hypochlorite ) in the bleach to be completely used up. The excess KI helps keep the l2 in solution.

Question 42

2011) (i)What was the pupose of standing the conical flask on a white tile during the titrations? (ii)Name the indicator used in the titrations and state the colour change observed at the end point.

Answer 42

So that the colour change can be seen more clearly. Starch, colour change at the end point is blue black to colourless.

Question 43

2007) Sodium tiiosuliare 1S Dot a PmidY Stae Describe how the crystallıne thiosulfate was dissolved and how the solution was transferred to the volumetric flask and made up to exactly 500 cm

Answer 43

The sodium thiosulphate was transferred to a beaker that contains 100cm3 of deionised water. A wash bottle of deionised water was used to wash the clock glass into the beaker. A glass stirring rod was used to help the thiosulphate dissolve. The contents of the beaker were transferred to a volumetric flask that had previously been washed out with deionised water, a funnel was used. The beaker and glass stirring rod were washed into the volumetric flask with deionised water. A dropper of deionised water was used to make up to the mark, the flask was stoppered and inverted 20 times.

Question 44

2003) How was the end-point detected?

Answer 44

The end point occurs when one drop of KMnO4 from the burette causes a colour change from colourless to pink.

Question 45

2007) Pure 1odıne is almost comlepletely insoluble in water. What must be added to bring 1odine into aqueous solution?

Answer 45

Potassium lodide solution was added.

Question 46

2007) A few drops of feshly prepared starch solutıon were added near the end pont as the indıcator for this titration. What sequence of colours was observed in the conical flask from the start of the titration until the end point was reached?

Answer 46

The flask starts of red / brown due to the formation of iodine. The sodium thiosulphate is added until the colour in the conical flask goes straw yellow. The starch is added and the colour goes blue/ black. A few drops more of sodium thiosulphate is added and the colour goes colourless. The reading is then taken from the burette.

Question 47

2015) Explain how iodine, a non-polar substance of very low water solubility, is brought into aqueous solution.

Answer 47

Potassium lodide ( KI) is added this is a source of lodide ions I which Combines with I, to form the triiodide ion ( la) which is soluble in water.

Question 48

2015) The iodine solution was made up in a 500 cm volumetric flask. Describe the procedure for measuring 25.0 cm' of this solution into a conical flask.

Answer 48

The iodine solution is poured into a clean dry beaker. The pipette is rinsed With deionised water and then some of the lodine solution that it is going to Contain. Using a pipette filler and a 25cm² pipette, the pipette is filled until the bottom of the meniscus is sitting on the mark. The pipette is alowed to drain into a conical flask under gravity. The pipette is touched against tne inside wall of the conical flask.

Question 49

Name a suitable indicator for this titration. At what stage is the indicator added? State the colour change at the end point in the presence of the indicator.

Answer 49

Starch solution is a suitable indicator. The indicator is added when the solution in the flask is straw yellow. The colour change at the end point is blue/ black to colourless.

Question 50

2002) What compound in white wine is converted to ethanoic acid in vinegar? What type of chenical process converts this compound to ethanorc acad?

Answer 50

Ethanol, Oxidation

Question 51

2002) Descrnbe the procedure for accuately measuring the 50 cm' sample of vinegar and diluting it to 500 cm

Answer 51

Rinse 5Ocm pipette with deionised water followed by some of the vinegar it is going to contain. Using a pipette filler, fill the pipette so the bottom of the meniscus is sitting on the mark. Rinse the 500 cm volumetric flask with deionised water, let the vinegar drain in to the volumetric flask. Touch the end of the pipette against the inside wall of the volumetric flask. Using a wash bottle/ dropper of deionised water make up to the mark on the neck of the flask. Stopper and invert 20 times.

Question 52

Name the piece of equipment that should be used to measure the ethanoic acid solution during the titation State the procedure for washing and filling this piece of equupment in preparation for the titration. Name a suitable ndcator for this titration

Answer 52

Burette, Rinse with deionised water followed by dilute vinegar. Using a funnel fill the burette up above the zero mark, allow some of the solution to run through the tap. Make sure the bottom of the meniscus is sitting on the zero mark and the burette is clamped vertically. Phenolpthalein ( Strong base vs Weak acid )

Question 53

2016) Describe in detail the procedures involved in measuring a 25.0 cm sample of the Vinegar and diluting it using deionised water to exactly 250 cm'.

Answer 53

The 25cm² pipette is rinsed with deionised water followed by the vinegar it is going to contain. Using a pipette filler the pipette is filled so that the bottom of the meniscus is on the mark on the neck of the pipette. The contents of the pipette are allowed to drain into the 20cm volumetric flask that had previously been rinsed by deionised water. The tip of the pipette is touched against the inside wall of the volumetric flask. Deionised water is added and a dropper is used to make the solution up to the mark so that the bottom of the meniscus is sitting on the mark. The flask is stoppered and inverted 20 times.

Question 54

2016) Name a suitable indicator for this titration. What colour change is observed at the end point?

Answer 54

Phenolpthalein. Pink to colourless.

Question 55

2016) Starting with a primary standard solution made from anhydrous sodium carbonate. what two titrations are required to standardise a sodium hydroxide solution?

Question 56

When the iron sulphate was being dissolved in water, another chemical was added, what was this chemical and why was it added?

Answer 56

Dilute sulphuric acid, added to stop the Fe2+ in the FeSO4 being oxidised by oxygen in the air or oxygen dissolved in the water.

Question 57

Why do you have to add dilute HzSO4 to the flask before carrying out the titration? What if you did not add the dilute HSO4 ?

Answer 57

To ensure that the KMnO4 is working at full oxidising power, i.e. is fully reduced from +7 to +2. If you don't add the acid, you would see a brown ( MnO2) +4 solution formed. (oxidation numbers for the Mn)

Question 58

During the titration, some chemical was splashed up on the side of the conical flask, what should you do?

Answer 58

Wash it down with a wash bottle of deionised water.