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Questions

Q1.Methyl orange and phenolphthalein are both acid-base indicators. In the titration of a strong acid against aweak alkali

A methyl orange is a suitable indicator but phenolphthalein is not.

B phenolphthalein is a suitable indicator but methyl orange is not.

C both phenolphthalein and methyl orange are suitable indicators.

D neither phenolphthalein nor methyl orange is a suitable indicator.

(Total for Question = 1 mark)

Q2.

When equimolar amounts of the solutions below are mixed, which forms a buffersolution with a pH less than !

A Hydrochloric acid and sodium chloride

B "thanoic acid and sodium ethanoate

C #odium hydroxide and sodium chloride

D $mmonia and ammonium chloride

(Total for question = 1 mark)

Q3.

$ buffer solution is made from ammonia and ammonium chloride. When a smallamount of acid is added to this buffer

A hydrogen ions in the acid combine with chloride ions to make H%l.

B hydrogen ions in the acid combine with &H'to make &H().

C &H()ions dissociate to make more &H'.

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D the hydrogen ions in the acid pre*ent dissociation of the &H(%l.

(Total for question = 1 mark)

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Q4.

Which of the following mixtures would form the best buffer solution with pH + for use in a schoollaboratory!

A "thanoic acid and sodium ethanoate

B #odium chloride and sodium hydroxide

C Hydrocyanic acid and sodium cyanide

D $mmonium chloride and ammonia

(Total for question = 1 mark)

Q5.

Which of the following mixtures would form the best buffer solution with pH for use in a schoollaboratory!

A "thanoic acid and sodium ethanoate

B Hydrochloric acid and sodium chloride

C #odium hydroxide and sodium methanoate

D $mmonium chloride and ammonia

(Total for question = 1 mark)

Q6.

Which one of the following indicators is most suitable for titrating ethanoic acid with . mol dm/'sodium hydroxide!

01efer to page + of your data booklet.2

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A 3hymol blue 0acid2

B 4romothymol blue

C 3hymol blue 0base2

D $li5arin yellow 1

(Total for question = 1 mark)

Q.

In a pH titration, ' cm'fo sodium hydroxide solution was added, in cm'portions, to 6 cm'of ethanoicacid solution, %H'%77H0aq2. 3he concentration of both solutions was . mol dm

/'. $fter the addition ofeach cm', the pH was recorded using a pH meter.

0a2 0i2 Write the Kaexpression for ethanoic acid.

(1)

0ii2 8sing your answer to 0i2, calculate the pH of the . mol dm/'ethanoic acid solution before thetitration starts. 1efer to page 9 of the data booklet.

(2)

0iii2 :educe the *olume of sodium hydroxide solution required to reach the end point.

(1)

.............................................................................................................................................

0i*2 %alculate the pH of the solution after all of the sodium hydroxide is added.

(4)

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0*2 7n the axes below sketch a graph to show how the pH changes during the titration.

(3)

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0b2 $n acidic buffer solution can be made by mixing together a solution of ethanoic acid and solid sodiumethanoate.

0i2 %alculate the mass of solid sodium ethanoate 0molar mass ; 96 g mol/2 that would be added to cm'of ethanoic acid, concentration . mol dm/', in order to make a buffer solution of pH ; (..

(4)

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Q!.

3he bubble bath =%olour %hange Matey= has amongst its ingredients the weak acidben5oic acid, as well as the indicator bromocresol green. When it is added to bathwater, its colour changes from yellow to blue.

0a2 0i2 Write the Kaexpression for the dissociation of ben5oic acid, %>H%77H.

(1)

0ii2 8se the data on page 9 of the data booklet to calculate the pH of a solution of ben5oic acid,%>H%77H, of concentration .6 mol dm

/'.

(2)

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Q".3he titration cur*es below were obtained using different acids and bases, each with concentration .mol dm/'.

0a2 Which cur*e is produced by adding ammonia to 6 cm'of hydrochloricacid!

(1) A

B

C

D

0b2 Which cur*e is produced by adding ethanoic acid to 6 cm'of sodiumhydroxide!

(1) A

B

C

D

0c2 $n indicator with pKIn9. is suitable for the following titrations.(1)

A 3itrations Aand Bonly.

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B 3itrations A, Band Donly.

C 3itration Conly.

D 3itrations A, B, Cand D.

(Total for question = 3 marks)

Q1#.

?inegar is used as a food preser*ati*e. It is an acidic solution containing ethanoic acid, %H'%77H.

0a2 $ titration was carried out to measure the concentration of ethanoic acid in a sample of *inegar.6. cm'of a *inegar solution was titrated with a solution of sodium hydroxide, concentration .6 moldm/'. 3he concentration of the ethanoic acid in the *inegar solution was found to be .6 mol dm/'.

0i2 %alculate the pH of .6 mol dm/'sodium hydroxide at 6+9 @.AKw; . B

/(mol6dm/>at 6+9 @.C(2)

0ii2 Write the expression for the acid dissociation constant, Ka, for ethanoic acid.(1)

0iii2 %alculate the pH of .6 mol dm/'ethanoic acid at 6+9 @.AKafor ethanoic acid is . B

/mol dm/'at 6+9 @.C(2)

0i*2 When half the ethanoic acid is neutrali5ed, the concentration of the remaining ethanoic acidequals the concentration of the sodium ethanoate which has formed. What is the pH of the mixtureat this point! Dustify your answer.

(2)

pH

.............................................................................................................................................

Dustification

.............................................................................................................................................

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0*2 7n the axes below, sketch the titration cur*e for this reaction when ' cm'of the sodiumhydroxide is added to 6. cm'of the *inegar solution.

(3)

.

"thanoic acid can neutrali5e alkalis. What substance could be mixed with ethanoic acid so that itregulates pH as a buffer in foodstuffs!

(1)

.............................................................................................................................................

(Total for question = 13 marks)

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