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Acids, bases and salts Questions

1. Study the reaction below and answer the questions that follow

NH3
(g) + H2O (l) NH4+ (aq) + OH(aq)

(a) Define the term acid

(b) Identify an acid in the above reaction  

(c) Explain your answers in (b) above  

2. A student mixed equal volumes of Ethanol and butanoic acid. He added a few drops of

concentrated Sulphuric (VI) acid and warmed the mixture

(i) Name and write the formula of the main products  

Name………………………………….

Formula……………………………………..

(ii) Which homologous series does the product named in (i) above belong?

 

3.   A sample of water from a village in Trans Mara East District was divided into equal portions

  and each mixed with equal volume of soap solution. The observations made are tabulated below:

 

ecolebooks.com

Sample of water

Treatment before adding soap

Observations made on shaking with soap

I

Boiled

Lather form immediately

II

No treatment

Slight lather form slowly

III

Treatment with washing soda

Lather formed immediately

 

(a) What type of hardness is present in water from the village. Explain

 (b) State one advantage of hard water  

4.  The solubility of Iron (II) Sulphate crystals are 22oC is 15.65g per 100g of water. Calculate

the mass of iron(II) sulphate crystals in 45g of saturated solution at the sae temperature  

 

5.  Hardness of water may be removed by either boiling or addition of chemicals:

 (a) Write an equation to show how boiling removes hardness of water

 (b) Name two chemicals that are used to remove hardness of water  

 

6.   State one advantage of drinking hard water rather than soft water.

 

7 Given this reaction;

RNH2 + H2O RNH3+ +OH

a) Identify the acid in the forward reaction .Explain

b) Dilute nitric acid can react with a solution of sodium carbonate. Write an ionic equation

for the reaction  

8.  Magnesium hydrogen carbonate is responsible for the temporary hardness of water.

 This type of hardness can be removed by addition of ammonia solution

  (a) Describe how temporarily hard water is formed

b) Write an equation to show the softening of temporarily hard water by the addition

of aqueous ammonium solution

 

9.  When 2M potassium hydroxide solution was added to solution R, a white precipitate T was

 formed which dissolved in excess potassium hydroxide solution to form solution L. solution

 R forms a white precipitate with sodium chloride solution:  

 (a) Identify the cation in solution R  …………………………………………………………….

 (b) Name precipitate T ……………………………………………………………………  

 (c) Write the molecular formula of the compound in solution L  

 

10.  Below is a table showing the solubilities of salts Q and R at different temperatures.

Temperature oC

 

0

10

20

30

40

50

Solubilities in grammes per 100g of water

Salt Q

3.0

5.0

7.4

10.0

14.0

19.0

Salt R

15.0

17.0

20.7

25.7

28.7

33.0

 

(a) Define the term “Solubility of salt”  

 (b) If both salts Q and R are present in 100cm3 of saturated solution at 50oC, what will

be the total mass of crystals formed if the solution was cooled to 20oC?

11.  The following results were obtained during an experiment to determine the solubility of potassium

 chlorate(V)in water at 30ºC.

 Mass of evaporating dish =15.86g

 Mass of evaporating dish + saturated solution at 30ºC = 26.8g

 Mass of evaporation dish +solid potassium chlorate (v) after evaporation to dryness=16.86g

 Calculate the mass of the saturated solution containing 60.0g of water at 30ºC    

12. (a) What is meant by the term solubility of salts?  

  (b) Calculate the solubility of salt given that 15g of the salt can saturate 25cm3 of water

(c) The table below gives the solubility of salt X in grams per 100g of water at different

temperatures

Temp oC

10

20

30

40

50

60

70

80

90

100

Solubility (g/100g) water

5.0

7.5

10.5

14.0

18.5

24.0

30.0

38.0

46.0

50.1

 

(i) Plot a solubility curve for salt X (solubility in g /100g water Y- axis) (temp oC (X –axis)

(ii) What is meant by the points plotted in (i) above?…………………………………………………………

(iii) From your graph determine the solubility of salt X at the following temperatures

I 44oC  ………………………………………….

II 62oC  ………………………………………. .

(iv) What mass of crystals of the salt will be formed if the solution was cooled from

62oC to 44oC

(v) Name two areas where knowledge of solubility curves is applied    

13.  You are given a mixture of Lead (II) Chloride, Iodine, ammonium chloride and sodium chloride.

Explain how you would separate all the four solids using methylbenzene, a source of heat and

water

14.  (a) The table below shows the solubility of potassium chlorate at different temperatures

 

Temperature (oC )

10o

20o

30o

40o

50o

60o

70o

Solubility g/100g water

27

30

36

55

80

110

140

 

  (i) Plot a graph of solubilities of potassium chlorate against temperature

 (ii) Using your graph:

(I) Determine the solubility of potassium chlorate at 47oC  

 (II) Determine the concentration in moles per litre of potassium chlorate at 47oC

(K= 39, Cl = 35.5, O= 16) density of solution = 1g/cm3

(III) Determine the mass of potassium chlorate that would crystallize if the solution

is cooled from 62oC to 45oC  

 (b) In an experiment to determine the solubility of sodium hydroxide, 25cm3 of a saturated

  solution of sodium hydroxide weighing 28g was diluted in a volumetric flask and the

volume made to 250cm3 mark. 20cm3 of this reacted completely with 25cm3 of 0.2M

hydrochloric acid according to the equation.

NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)

 

 Calculate:

 (i) The number of moles of hyrdrochloric acid used

 (ii) The number of moles of sodium hydroxide in 20cm3

 (iii) The moles of sodium hydroxide in 250cm3 of solution

 (iv) The mass in grams of sodium hydroxide in 250cm3 of solution  

 (v) The solubility of sodium hydroxide in g/100g water

15.  a) Define the term solubility of a substance  

 b) The table below shows the solubilities of two salts L and M at different temperatures.

 

Temperature(ºC)

10

20

30

40

50

Solubility in g/100g

of water.

L

11.0

14.0

20.1

28.0

36.0

M

15.0

17.0

19.0

21.2

25.0

i) Name the method that can be used to separate the two salts  

ii) Plot on the same axes a graph of solubilities of L and M against temperature

iii) From the graph determine:-

The temperature at which solubilities are equal

The solubility at the temperature mentioned above

iv) If the relative formula mass of M is 132, determine the concentration of M in moles per litre

in (iii) II above  

 

16.  The graph below shows the changes in conductivity when 50cm3 of 0.1M Nitric (V) acid

is titrated with potassium hydroxide (curve I) and when 50cm3 of 0.1M methanoic acid is

reacted with the same potassium hydroxide solution (curve II)

 

 

 

Image From EcoleBooks.com

 

 

 

 

 

 

 

 

 

 

 

Image From EcoleBooks.com

 

 

 

 

 (a) (i) Explain the changes in conductivity in the regions:


AB……………   BC………………………………………………….  

(ii) Using curve (I), explain why the conductivity does not have a value of zero

at end-point  

(iii) Calculate the concentration of KOH with reference to curve II

(iv) Explain why the two curves shows different trends in conductivity

 (b) 50cm3 of 0.1M methanoic acid was reacted with 20cm3 of a solution of sodium

carbonate of unknown concentration. Work out the concentration of the carbonate  

 

17.  The flow charts below show an analysis of a mixture R that contains two salts. Study the

 analysis and answer the questions that follow:-

Image From EcoleBooks.com (a)

Image From EcoleBooks.comImage From EcoleBooks.com

Image From EcoleBooks.comImage From EcoleBooks.comImage From EcoleBooks.comImage From EcoleBooks.com

 

Image From EcoleBooks.comImage From EcoleBooks.comImage From EcoleBooks.com

Image From EcoleBooks.com

 

 

 

(i) State:-  

(I) The condition in step I

(II) The process in step II  

(ii) A small portion of mixture R is added to dilute nitric (V) acid in a test-tube. What would be

observed?

(iii) Write an equation for the reaction between the cation in filtrate X and sodium hydroxide

solution

(iv) Explain how water vapour in step I could be identified

 
 

(b)

 

 

 

 

 

 

 

 

 

 

 

(i) State and explain the conclusion that can be made from step IV only

(ii) Name the anion present in residue U. Explain

 

(iii) From the flow chart in (a) and (b);

(I) Write the formulae of cations present in mixture R

 

18.  a) Define the term solubility of a substance.  

 b) The table below shows the solubilities of two salts L and M at different temperatures.

 

Temperature (oC)

Type of salt

10

20

30

40

50

Solubility g/100g of water

L

11.0

14.0

20.1

28.0

36.0

M

15.0

17.0

19.0

21.2

25.0

 

 (i) Name the method that can be used to separate the two salts.  

 (ii) Plot on the same axes a graph of solubilities of L and M against temperature

 (iii) From the graph, determine:

I. The temperatures at which solubilities are equal

 II. The solubility at the temperature mentioned above    (iv) If the relative formula mass of M is 132, determine the concentration of


M in moles per litre in (iii) II above.

 v) A solution contains 38g of L and 22g of M at 50°C. Calculate the total mass of crystals

obtained in cooling this solution to 30°C.  

 

19.  a) Define:

  (i) A saturated solution.  

  (ii) Solubility of a solute.  

 b) In an experiment to determine solubility of sodium chloride, 10.0 cm3 of a saturated solution of

sodium chloride weighing 10.70g were placed in a volumetric flask and diluted to a total of 500

cm3. 25.0 cm3 of the diluted solution of sodium chloride reacted completely with 24.0 cm3 of

0.1M silver nitrate solution. The equation for the reaction is

AgNO3(aq) + NaCl (aq) AgCl (s) + NaNO3 (aq)

I. Calculate;  

  (i) Moles of silver nitrate in 24.0 cm3 of solution.  

  (ii) Moles of NaCl in 25.0 cm3 of solution.  

  (iii) Moles of NaCl in 500 cm3 of solution.  

  (iv) Mass of NaCl in 10.0 cm3 of saturated sodium chloride (Na = 23, Cl = 35.5)

  (v) Mass of water in 10.0cm3 of saturated solution.

  (vi) The solubility of NaCl in g/100g of waters.  

 

 

20.  Describe how you would prepare a dry sample of crystals of potassium sulphate starting with

 100cm3 of 1M sulphuric (VI) acid.    

21.  The table shows solubility of potassium chlorate V

Temp (oC)

45oC

80o

Solubility

39

63

 (a) Calculate the mass of solute and solvent in 90g of the saturated solution of the salt at 45oC

  (b) A solution of the salt in 100g water contains 63g at 95oC. At what temperature will the

  solution start forming crystals when cooled

22.  Two samples of hard water C and D were boiled. When tested with drops of soap, sample


D formed lather easily while C did not:-

  (a) Name the possible salt that caused hardness in sample D  

 (b) Explain how distillation can remove hardness in sample C  

 (c) Give one advantage of hard water

23.  A student attempted to prepare a gas using the set-up below. She could not collect any gas

 

Image From EcoleBooks.com

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 
 

 

 

(a) Give two reasons why no gas was collected

 (b) Which gas did the student intend to prepare?

24.  Water from a town in Kenya is suspected to contain chloride ions but not sulphate ions.

 (a) Describe how the presence of chloride ions in the water can be shown

 (b) State one advantage of drinking hard water rather than soft water

25.  Study the following tests and observation and answer the questions that follow:-

 

TEST

OBSERVATION

I

– Add few drops of acqueous ammonia to copper (II) nitrate solution

– Light blue precipitate is formed

II

– Add excess of ammonia to copper (II) nitrate

– Deep blue solution

III

– Add cold dilute hydrochloric acid to substance E1 and warm gently

– Gas evolved, smells of rotten eggs and blackens lead acetate paper

Identify:-

(a) Substance responsible for:

  I. Light blue precipitate…………………………………………………………………  

  II. Deep blue solution  …………………………………………………………….  

 (b) Gas evolved in test III above …………………………………………………………  

 

26.  (i) What is meant by the term solubility of salts?

 (ii) Calculate the solubility of a salt given that 15g of the salt can saturate 25cm3 of water.  

27.  (a) Draw a well labeled diagram to show how to prepare an acqueous solution of hydrogen

chloride gas

 (b) Name one other gas whose aqueous solution can be prepared in the same way

28.  In an experiment to determine the solubility of solid Y in water at 30oC the following results

  were obtained;  *MAT

Mass of empty evaporating dish = 26.2g

Mass of evaporating dish + saturated solution = 42.4g

Mass of evaporating dish + dry solid Y = 30.4g

 (a) Use the data to calculate the solubility of solid Y at 30oC  

 (b) State one application of solubility curves and values

 

29.  Study the table below showing the solubility of substance K at various temperatures

Temperature (oC )

Solubility (g/100g water)

0

30

70

100

30

24

19

14

 

 

 

 

 

 

  (a) What would happen if a sample of a saturated solution of the substance at 30oC is

heated to 70oC. Explain.

 (b) What is the most likely state of substance K…………………………………………………………

30.  In the equilibrium given below:-

 Fe3+(aq) + SCN(aq)   [Fe(SCN)]2+
(aq)

 Brown Red

What would be observed when Iron (III) Chloride is added to the equilibrium mixture. Explain  

31. Sodium Carbonate Decahydrate crystals were left exposed on a watch glass for two days.

a) State the observations made on the crystals after two days.

b) Name the property of salts investigated in the above experiment  

 

32.  The label on a bottle of mineral; water had the information below.

Ions present

Concentration (g/litre)

Ca2+

Mg2+

Na+

Image From EcoleBooks.comK+

Image From EcoleBooks.comSO4

HCO3

0.10

0.20

0.01

0.01

0.14

0.26

 

 

 

 

 

 

(a) Name the compound that causes temporary hardness in the mineral water.

 (b) Using an equation, describe how the water can be made soft by adding sodium

carbonate solution.

 (c) Give one advantage of drinking mineral water such as the one above

 

33.  A solution of hydrogen chloride gas in methylbenzene has no effect on calcium carbonate.

A solution of hydrogen chloride in water reacts with calcium carbonate to produce a gas. Explain  

34  (i) Is concentrated sulphuric acid a weak acid or a strong acid?  

 (ii) Explain your answer in (i) above.

35.   When water reacts with potassium metal the hydrogen produced ignites explosively

on the surface of water.

(i) What causes this ignition?

(ii) Write an equation to show how this ignition occurs

36. In an experiment, soap solution was added to three samples of water. The results below

show the volume of soap solution required to lather with 500cm3 of each water sample

before and after boiling

 

Sample 1

Sample 2

Sample3

Volume of soap used before water boiled

26.0

14.0

4.0

Volume of soap after water boiled

26.0

4.0

4.0

 

(i) Which water samples are likely to be soft?  

(ii) Explain the change in volume of soap solution used in sample 2

Image From EcoleBooks.com

37.   How does the pH value of 0.25M KOH(aq) compare with that of 0.25M ammonia solution

 

Acids, bases and salts Answers Answers

1. (a) Proton donor/electron acceptor/a substance which when dissolved in water

dissociates/break to Image From EcoleBooks.com hydrogen ions as the only positive ion.

( b) Water/ H2O  

(c) It is a proton donor/electron acceptor

2. (i) Ethylbutanoate

(ii) CH3CH2CH2

(iii) Esters

3.  (a) Temporary water hardness . This is because hardness is removed by boiling

 (b) – Provide Ca2+ ions needed in formation of strong teeth and bones

  – Hard water form a layer of carbonate of lead which prevent water coming in contact with

lead Image From EcoleBooks.com which cause poisoning  (award 1mk for any one)

Image From EcoleBooks.com4.  Let x be the mass of FeSO4 crystals in saturated solution

Image From EcoleBooks.com   Mass of water = 45 – x

 X g of FeSO4 dissolves in (45-x)g of water

 100x of FeSO4 dissolves in 100g of water

  45 – x

Image From EcoleBooks.comSo, solubility is 100x = 15.65

45 – x

100x = 15.56 (45 – x)

100x + 15.65x = 15.65 x 45

Image From EcoleBooks.com115.65x = 15.65 x 45

x = 15.65 x 45

115.65

= 6.0895

So solubility = 6.09g of FeSO4 in 100g of water

5 .   (a) Ca(HCO3)2(aq) CaCO3(s) + CO2 + H2O(l)

  or:- Mg(HCO3)
MgCO3(s) + CO2(g) + H2O(s) (award 1mk for any)

 

 (b)  – Addition of Na2CO3(s)

  – Addition of Ca(OH)2(s)

    – Addition of aqueous ammonia (award 1mk each for any two; Total =2mks)

6. – Provides essential minerals e.g. Ca2+ for strong bornes and teeth 1

  – It has a better taste

 

7.  a) The acid is water H2O

 Reason H2O has donated a proton (H+)

 b) 2H+(g) + CO32-(aq) ___________ CO2(g) + H2O(l)

8. Magnesium carbonate reacts w ith rain water

  • Containing caborn (iv) oxide dissolved.
  • Forming magnesuin hydrogencarbonate
  • Or MgCO3(s) + CO2(g) + H2O(l) + Mg (HCO3) 2 (aq)

 

Image From EcoleBooks.com9. (a) Lead ions

Image From EcoleBooks.comImage From EcoleBooks.com (b) Lead (II) hydroxide

(c) [Pb(OH)4]2-

 

10.  a) Solubility of a salt is mass of a salt that dissolves in 100g of water at a given temperature. √1

 b) Mass of Q that crystallizes out = 19.0 – 7.4 √½ = 11.6 g.

  Mass of R that crystallizes out = 33 – 20.7√½ = 12.3g.

  Total mass of crystals = 12.3 + 11.6√½ = 23.9g √½

 

11.   Mass of dry salt = 16.86 – 15.86 √ ½

= 1.00g √ ½

Mass of water = 26.86 – 16.86 = 10g√ ½

Mass of salt in 60g of water = 60×1 = 6 g √ ½

   10

12.   (a) This is the maximum mass of a salt that will dissolve in 100g of water of a given

temperature

  (b) 15g dissolve in 25cm3 water

? dissolve in 2100cm3 water

= 15 x 100 = 60g/100gwater

25

  (c) (i) in graph paper

(ii) Every point on the solubility curve is a saturated point of a solution which contains a

maximum amount of salt X at a graph temperature

Image From EcoleBooks.comImage From EcoleBooks.com (iii) I 16g

Image From EcoleBooks.com II 25g

(iv) 25 – 16 = 9g/100g water

Image From EcoleBooks.com (v) – Extraction of Na2co3 from Lake Magadi

– Extraction of Nacl from sea water

 

13.  Add Methyl benzene to the mixture and stir to dissolve iodine. Filter and crystallize the

filtrate to obtain sodium chloride crystals.

 

14.  (a) (ii) 72g /100g water  1.0

  (iii) 100cm3 dissolve 72g

Image From EcoleBooks.com   1000cm3 dissolve = (1000 x 72)

  100

Image From EcoleBooks.com   = 720g/l

Image From EcoleBooks.comKClO3 = 39 + 35.5 + 3 x 16 = 122.5

molarity = 720g/l

Image From EcoleBooks.com 122.5gmol-1

 = 5.878mol/l

Image From EcoleBooks.comImage From EcoleBooks.comImage From EcoleBooks.com(iv) Mass dissolved at 62o = 116g

  Mass dissolved at 42o= 66g

mass crystallized out = 50g

Image From EcoleBooks.com

(b) (i) (25 x 0.2M) = 0.005mol

 1000

 (ii) 0.005mol (mole ration Acid: Base = 1:1)

Image From EcoleBooks.com  (iii) 20cm3 contain 0.005mol

Image From EcoleBooks.com 25cm3 contain = (250cm3 x 0.005mol)

 20cm3

= 0.0625mol

Image From EcoleBooks.com

(iv) Mass = (0.0625x 4ogmol-1) = 2.5g

Image From EcoleBooks.comImage From EcoleBooks.com

(v) Mass of solvent = 28g – 2.5g = 25.5g

Image From EcoleBooks.com   solubility = (100 x 2.5)

Image From EcoleBooks.com 25.5

= 9.804g/100g water

15.  a) Solubility refers to the maximum mass of solute dissolving in a 100g of a solvent at a

particular temperature

 

 b)  i) Fractional crystallization

ii)   Scale = 1 mk

Plotting = 1 mk

Curve L = 1 mk

Curve M = 1 mk

iii) I = Actual value from students curve + 1C

II = Actual value from students curve + 1

 

iv) Mass per litre = 1000 X Actual value in iii (II)

100

 Concentration = Above answer

 132

= _________ M

16.  (a) (i) Conductivity decreases wince H+ ions form he acid are neutralized by OHions

from the base. This reduces the concentration of ions available for conductivity.

(ii) Conductivity increases since the OH ions accumulate after complete neutralization of the

acid OH increases conductivity.

(iii) Neutralization leads to the formation of a slat. The ions in the salt are responsible for

conducting of electricity.

(iv) They yield different concentration of H+ ions

For HNO3 – dissociates completely hence more H+ ions  

HCOOH – dissociates partially hence less H+ ions

 

(b) 2HCOOH(aq) + Na2CO3(aq) 2HCOONa(aq) + H2O(l) + CO2(g)

  moles of HCOOH = 50 x 0.1

  1000

= 0.005moles

mole ration acid : base

2 : 1

moles of Na2CO3 = 0.005

2

= 0.0025

Molarity of Na2CO3 = 0.0025 x 1000

20

= 0.125M

 

17.  a) i)  I) Heating √1

II) Filtration. √1

  ii) Effervescence √1 / Bubles.

  iii) Zn2+(aq) + 2OH(aq) Zn(OH)2(s) √1

  iv) Pass the water vapour over white anhydrous√1 Copper (II) suplhate. It turns blue. √½

 b) i) R is a mixture of sulphur √½ and insoluble√½ salt. It forms √1 a filtrate and residue in

filtration of mixture

  ii) Carbonate √1 / CO32-
√1

  It produces CO2 on reaction with H+

  iii) Zn2+√1 Al 3+ √1

18.  a) The quantity of a substance in grammes that can dissolve in 100g of water at a given

temperature

 

 b)  i) Fractioned crystallization

ii)

iii)

I  26C

II   18g

 

iv) 1 mole of salt M _______ 132g

18×1/132 = 0.13863636 moles

Concentration = 1000 x 0.13863636

100

= 1.386M

v) L = 20g M= 19g

38-20=18

22-19= 3+

 Total 21 g

19.  (a) (i) A saturated solution is one which cannot dissolve more solute at that particular temperature.

  1 (1 mk)

  (ii) Solubility of a soluble is the amount of grams of solute present in 100g of water at that

  particular temperature. 1 (1 mk)

 

 (b) (i) Mole = M x V

1000

 

 0.1 x 24
1  = 0.0024 moles1 (2 mks)

1000

 

  (ii) Moles of NaCl in 25cm3

Mole ratio is 1 : 1

Moles of NaCl = 0.0024 moles1 (1 mk)

 

  (iii) Moles of NaCl in 500 cm3

If 25cm3 = 0.0024 moles

∴ 500 cm3 = ?

= 500 cm3
1 x 0.0024 moles

25 cm3  

= 0.048 moles 1  (2 mks)

 
 

  (iv) Mass of NaCl in 10cm3

  Mass = moles x R.F.M.

= 0.048 x 58.5 = 2.808g

 
 

  (v) Mass of water = mass of solution – mass of NaCl

= (10.70 – 2.808)g 1  

= 7.892 g 1 (2 mks)

 

  (vi) If 7.892 of H2O
2.808g 1  

100g of H2O ?

 100g x 2.808 1  

 7.892g

 = 35.6g /100g of H2O1  

 

20.  Add 100cm3 of 2M √ potassium hydroxide or 200cm3 of 1M potassium hydroxide to the acid.

Heat the solution until it is saturated and cool to obtain crystals. Dry the crystals between

filter papers

 

21.  (a) 139g of solution contains 39g solute

  90kg of solution contains 39 x 90 = 25.25g

  139

Mass of solvent = 90 – 25= 64.75g  

  (b) 80oC

 

22.  (a) Calcium hydrogen carbonate/Magnesium hydrogen carbonate;

(b) Water boils off and is condensed leaving the salt;

(c) Provides minerals used to strengthen bones

 

23.  (a) Delivery tube should not dip into solution

  – Thistle funnel should did into the solution

  – Gas jar was no water/ little water in trough  ( 1 each max 2)

  (b) Oxygen

 

24.   a) acidity water with Nitric add aqueous lead nitrate or

  – silver nitrate formation of white precipitates shows presence

penalize fully for uric acid 1 ½ mk   of chloride ions

 b) provide essentials minerals e.g. Ca2+ ions

 

25. a) I- Cu (OH)2 or copper (II)hydroxide√1

b) Cu(NH3)4
2+√1

c)Hydrogen sulphide or H2Sg√1

 

26. i)this is the maximum mass of a salt that will dissolve in 100g of water at a given temperature √1

ii)15g dissolve in 25cm³ water

xg dissolve in (15×100)g√1

25

= 60g/100g√1

27.   (a) Diagrammatical presentation on how to prepare an aqueous solution of hydrogen

chloride gas

 

 

 

 

 

 

 

 

 

 

 

 

 (b) Ammonia gas  *MAT

 

28.  Mass of saturated soln. = 42.4 – 26.2 = 16.2

Mass of dry solid Y = 30.4 – 26.2 = 4.2g/12.0

Solubility of Y = 4.2 x 100

  12.0

35g per 100g of water

 (b) – Used is fractional crystallization of salt mixture.

 

 

29.  (a) 24 -19 = 5g of substance K will be produced

Image From EcoleBooks.com  Reason: Solubility decreases with increase in temperature

 (b) Gaseous state

Image From EcoleBooks.com30.  Deep red solution will be formed. Equilibrium shifts to the right/forward reaction is favoured since Fe3+ ions favours forward reaction.

 

31.  a) They became a white powder

 b) Efflorescency

 

32.  a) calcium hydrogen carbonate/ magnesium hydrogen carbonate

 

 b) Ca(LHCO3) 2(aq) + Na2CO3(aq) ________ CaCO3(g) + 2NaHCO3(aq)

 

  Mg(HCO3)2(aq) + Na2CO3(aq) ________ CaCO3(g) + 2NaHCO3(a)

 

 c) Contains Ca2+ ions needed to harden teeth and bones

 

33.  HCl g in water ionizes to produce H+
aq and Cl
aq

 HCl (g) in methylbenzene remain as moles hence no H+ ion

 

 

34.  (i) Weak acid 1

 (ii) Has few free H+ (Hydrogen) ions

 

35.  (i) The reaction is too exothermic that alot of heat is produced causing ignition of

hydrogen in presence of oxygen

 (ii) K(s) + H2O(g) KOH(aq) + H2(g)

H2(g) + O2(g) H2O(g)  

 

Image From EcoleBooks.com36. (i) Sample 1 and 2  

(ii) Sample 2 contained ions that caused temporary hardness therefore required

large ( volume of soap solution before boiling, but after boiling the temporary hardness

was removed, hence requiring very little volume ( ½mk) of soap solution to lather.  

Image From EcoleBooks.com 37.- KOH has higher pH value than ammonia

Image From EcoleBooks.com   – KOH is a stronger base; dissociates fully

  – Ammonia solution is a weak base; dissociates partially




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EcoleBooks | 18. Acids, bases and salts Questions and Answers

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