9. Salts Questions and Answers

Salts Questions

1. Study the flow chart below and answer the questions that follow:

 a) Name reagent Z.

 b) Describe the process which takes place in step 2.

 c) Identify the white solid.

2. a) Starting from solid magnesium oxide, describe how a solid sample of magnesium hydroxide

can be prepared.

 b) Give one use of magnesium hydroxide.

3. Starting with lead (II) oxide, describe how you would prepare a solid sample of

lead (II) Carbonate

4. Study the diagram below and answer the questions that follow:

(a) Name the two salts formed in tube A

 (b) State the observations made in tube C

(c) Name gas P

5. Study the information in the table below and answer the questions that follow:-

(a) Complete the table by filling in the blank spaces (i) , (ii) (iii), and (iv)

 (b) Identify the particles which are electrically charged

6. 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

7. Starting with sodium oxide, describe how a sample of crystals of sodium hydrogen carbonate

may be prepared

8. In an experiment, ammonium chloride was heated in test-tube. A moist red litmus paper

placed at the mouth of test first changed blue then red. Explain these observations:-

9. Using dots (•) and cross (x), show the structure of ammonium ion

10. a) Give the name of each of the processes described below which takes place when salts are

exposed to air for sometime

 i) Anhydrous copper sulphate becomes wet

 ii) Magnesium chloride forms an aqueous solution

 iii) Fresh crystals of sodium carbonate, Na₂CO₃.10H₂O become covered with white powder

of formula Na₂CO₃.H₂O

 b) Write the formula of the complex ion formed in each of the following reactions described

below;

i) Zinc metal dissolves in hot alkaline solution

ii) Copper hydroxide dissolves excess ammonia solution

11 (a) Write an equation to show the effect of heat on the nitrate of:-

 (i) Potassium

 (ii) Silver

12. (a) The scheme below shows some reactions starting with magnesium oxide. Study it and

answer the questions that follow:-

(i) Name the reagents used in steps 2
and
4

 (ii) Write an equation for the reaction in step 3

(iii) Describe how a solid sample of anhydrous magnesium carbonate is obtained in step 5

13. In the preparation of magnesium carbonate, magnesium was burnt in air and the product

collected. Dilute sulphuric acid was then added and the mixture filtered and cooled. Sodium carbonate was added to the filtrate and the contents filtered. The residue was then washed and dried to give a white powder.

 (a) Give the name of the product

 (b) Write the chemical equation for the formation of the product

 (c) (i) Name the filtrate collected after sodium carbonate was added.

(ii) Write down the chemical formula of the white powder

 (d) Write a chemical equation for the reaction between product in (a) and the acid

 (e) Write an ionic equation to show the formation of the white powder.

 (f) Write an equation to show what happens when the white powder is strongly heated.

 (g) Identify the ions present in the filtrate after addition of sodium carbonate.

 (h) What is the name given to the reaction that takes place when sodium carbonate was

added to the filtrate?

(i)Explain the observations made when crystals of sodium carbonate decahydrate are left

exposed to the atmosphere for two days

14. a) Give the name of each of the processes described below which takes place when salts are

exposed to air for sometime

 i) Anhydrous copper sulphate becomes wet

 ii) Magnesium chloride forms an aqueous solution

 iii) Fresh crystals of sodium carbonate, Na₂CO₃.10H₂O become covered with white powder

of formula Na₂CO₃.H₂O

15. You are provided with the following:- solid lead (II) nitrate, magnesium oxide powder,

dilute sulphuric (VI)acid and distilled water. Describe how you can prepare a dry sample

of lead (II) sulphate

16. Use the scheme to answer the questions that follow:

(a) Identify solid N ……………………………………………………………….

(b) Write a balanced equation for the formation of Q

(c) Write the formula of the complex ion formed when sodium hydroxide is added to

solution L in excess

17. When exposed to air, crystals of hydrated sodium carbonate loses water of crystallizations;-

 (i) Name this process

 (ii) Write the formula of hydrated sodium carbonate

18. A student poured sodium iodide solution into a small portion of solution Q, a yellow

precipitate was formed.

 (i) Which ion was most likely in solution Q?

 (ii) Write an ionic equation leading to the formation of the yellow precipitate

19. Calcium oxide can be used as a solid drying agent for some laboratory gases. Explain

20. A piece of marble chips was strongly heated in air for about 30 minutes. Some drops of water

were added drop by drop to the product when it was still warm.

Using equation, explain:

(i) What happens when the piece of marble chips is heated?

(ii) The reaction that takes place when water is added to the final warm product.

21. Study the flow chart below and answer the questions that follow

a) Identify

i) gases C and B

ii) Ions likely to be presented in solid A

22. Potassium nitrate crystals in a test-tube were heated strongly for some time. State the

observation made:

(a) When a glowing splint is introduced into the test-tube during the heating

(b) At the end of the heating

23. Name the process which takes place when:

 (a) Anhydrous iron (III) chloride absorb water vapour from the air to form solution

 (b) Zinc chloride vapour changes directly to zinc chloride solid

24. (a) Starting form solid magnesium oxide, describe how a solid sample of magnesium

hydroxide can be prepared

 (b) Give one use of magnesium hydroxide

25. The diagram below represents a set-up that was used to show that part of air s used during burning

 (a) State two sources of errors in this experiment

26. In an experiment the following solids were provided to form three students; Ca(NO₃)_2(s),

NaH₂PO_4(s) Mg(OH)Cl_(s) and Fe(NH₄)₂(SO₄)₂. 6H₂O. They were then told to dissolve the

given solids in differently in 20ml of water.

(a) Classify the given salts accordingly

 (b) (i) Explain the process which takes place when FeCl₃ is dissolved in water

(ii) A student placed a moist litmus paper on the product in (i) above. State and explain the

observation made

4. Salts Answers

1. a) Conc. H₂SO₄ / H₂SO4

 b) Heat the solution to concentrate it.

Allow for crystals to form ½ Filter ½

 c) Anhydrous Copper(II) sulphate/CUSO₄(s)

2. a) To MgO, add excess HNO_3,½ HCl or H₂SO₄ . Add NaOH or KOH or NH₄OH to the

mixture, ½ Filter  ½ and dry ½ the residue.

b) – Anti-acid (Treatment of acid indigestion)

– Making tooth past 1

3. Add excess lead (II) Oxide to dilute nitric (v) acid and filter to get lead (II) nitrate solution.

Add sodium carbonate solution to lead (II) nitrate to precipitate lead (II) carbonate and wash

with distilled water.

4. a) Sodium nitrate/ sodium nitrite

 b) Black charcoal glows red

Grey ash formed

 c) carbon (II) oxide

5. .a)

 b) E,G and H

6. a) They became a white powder

 b) Efflorescency

7. Add water to sodium oxide to form sodium hydroxide solution. Bubble excess carbon (IV) oxide

in sodium hydroxide solution to form sodium hydrogen carbonate. Heat sodium hydrogen

carbonate solution to evaporate water.

8. NH₄Cl decomposes on heating to produce NH₃ and HCl (g). NH_3(g) is lighter than HCl_(g)

hence diffuses faster and turns red-litmus to blue HCl is denser hence diffuses at a slower rate: changes blue litmus to red

9.

10. a) i) Hydroscopy// hygroscopic

ii) Deliquescence// Deliquescent

iii) Efflorescence// Efflorescent

 b) i) Zn(OH)₄^2-

ii) Cu(NH₃)₄²⁺

11. (a) (i) 2KNO_3(s) 2KNO_2(s) + O2(g)- ½mk for wrong states

(ii) 2AgNo_3(s) 2Ag_(s) + 2NO_{2 (g)} + O_{2 (g)}

12. (a) (i) Carbon (iv) Oxide

 Dilute hydrochloric acid

(ii) Mg(HCO₃)_2(aq) MgCO_{3 (s)} + H₂O_(l) + CO_2(g)

(iii) Add sodium carbonate/any soluble carbonate (named ) solution;

Filter

Dry the residue between two filter papers

13. a) magnesium Oxide

 b) 2Mg_(s) + O2_(g) _________ 2MgO_(s)

 c) i) Sodium sulphate

ii) MgCO₃

 d) MgO_(s) + H₂SO_4(aq) ________ M_gSO_4(aq) + H₂O_(L)

 e) Mg²⁺_(aq) + CO^2-
_3(aq)________ M_gCO_3(s)

f) M_gCO_3(g) _________ M_gO_(g) + CO_2(g)

 g) Na⁺ ions and SO₄^2- ions

 h) Precipitation/ double decomposition

 i) Crystals turn to a white powder. The salt is efflorescent hence it looses its water of

crystallization forming a powder

14. a) i) Hydroscopy// hygroscopic

ii) Deliquescence// Deliquescent

iii) Efflorescence// Efflorescent

 b) i) Zn(OH)₄^2-

ii) Cu(NH₃)₄²⁺

15.

• Dissolve lead (ii) nitrate crystal in a given amount of distilled water in a beaker
  
• To dilute sulphuric√ ½ (vi) acid in a beaker add magnesium√ ½ oxide powder
  
• React the two solutions obtained
  
• Filter the mixture
  
• Dry the residue between filter papers to obtain a dry sample of lead (ii) sulphate
  

16. (a) Zinc oxide √1 ZnO (1 mk)

 (b) ZnO_(s) + H₂SO_4(aq) √1 ZnSO_4(aq) + H₂O (1 mk)

3

 (c)

Zn (OH) √1 (1 mk)

17. (i) Efflorescence

(ii) Na₂ Co₃.10H₂O (If letters are joined – no mark)

18. (i) Pb²⁺

 (ii) White precipitate formed soluble in excess

19. Calcium oxide hygroscopic atmospheric water vapour ad becomes wet

Some laboratory gases are acidic

While calcium oxide is basic

Therefore calcium oxide reacts with the gas//calcium oxide would absorb the gas

20. A piece of marble chips was strongly heated in air for about 30 minutes. Some drops of water

were added drop by drop to the product when it was still warm.

Answers

i) It decomposes to give Calcium oxide/Lime and Carbon (IV) oxide

 CaCO_3(s) CaO_(s) + CO_2(g)

 ii) Alot of heat is evolved which makes the piece of lime swell hence the name quick lime and

Calcium hydroxide(slaked lime) is formed.  ½

 CaO(s) + H₂O(l) Ca(OH)₂(aq) 1

21. a) i) Gas C O_2(g)
 ½ Gas B NO₂  ½

ii) Zn²⁺ and NO₃⁺ ½

 b) ZnO_(g) + 2HNO_{3 (aq)} ________ Zn(NO₃)_2(aq) + H₂O_(l)

Balanced

State symbols

Chemical symbols

22. (a) Glowing splint is relighted/rekindles

 (b) Pale yellow solid

23. a) Deliquescence√1

b) Deposition √1

24. a)- To MgO add excess HNO₃ √ ½ (Or HCL or H₂ SO₄)

– Add NaOH or KOH or NH4 OH to the mixture √ ½

– Filter and dry the residue√1

b) Uses as

– Anti – acid or tooth paste √

25) – Dil NaOH may not absorb all the carbon (IV) oxide gas produced

– Candle may go off before all the oxygen is used due to build up carbon (IV) oxide

26 a) Acid salts NaH₂PO_4(S) √1

Basic salts – M_g (OH) CL_(s) √1

Normal salts – Ca (NO₃)_2(S) √1

Double salt – Fe(NH₄)₂ (SO₄)₂ 6H₂O√1

b) i) Hydrolysis – Reaction of water with a compound to form at least two products √1

ii) Moist litmus paper turns red due to the HCL gas produced √1

Or accept equation for the explanation

FeCL_3(S) + 3H₂O_(L) Fe (OH)_3(S) + 3HCl _(g)