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5. Water and hydrogen Questions

1.  (a) Hydrogen can reduce coppers Oxide but not alluminium oxide. Explain  

 (b) 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

 

 

Image From EcoleBooks.com2.  In an experiment, dry hydrogen gas was passed over hot copper (II) oxide in a combustion

tube as shown in the diagram below:-

 

 

 

 

 

 

ecolebooks.com

 

 

 

 

 

 

 (a) Complete the diagram to show how the other product, substance R could be collected

in the laboratory.  

 (b) Describe how copper could be obtained from the mixture containing copper (II) oxide  

Image From EcoleBooks.com3. The setup below was used to investigate the reaction between metals and water.

 

 

 

 

 

 

 

 

 

 

 

(a) Identify solid X and state its purpose

Solid X ………………..………………………………………………………………………..

Purpose ………………………………………………………………………………………..

(b) Write a chemical equation for the reaction that produces the flame.  

4.  Gas P was passed over heated magnesium ribbon and hydrogen gas was collected as shown

Image From EcoleBooks.com in the diagram below:

Image From EcoleBooks.com

 

Image From EcoleBooks.com

 

 

 

Image From EcoleBooks.com

 

 

 

 

 

 (i) Name gas P  …………………………………………………………………………………………………

 (ii) Write an equation of the reaction that takes place in the combustion tube

 (iii) State one precaution necessary at the end of this experiment  

5. When hydrogen is burnt and the product cooled, the following results are obtained as shown

in the diagram below:

 

 

 

 

 

 

 

 

 

 

(a) Write the equation for the formation of liquid Y

(b) Give a chemical test for liquid Y

6.  Jane set-up the experiment as shown below to collect a gas. The wet sand was heated before

Image From EcoleBooks.com  heating Zinc granules

 

 

 

 

 

 

Image From EcoleBooks.com

 (a) Complete the diagram for the laboratory preparation of the gas  

 (b) Why was it necessary to heat wet sand before heating Zinc granules?

 

Image From EcoleBooks.com7.

 

 

 

 

 

 

 

 

 

Image From EcoleBooks.com

 

 

 
 

 

 

 

 

 

(a) Between N and M which part should be heated first? Explain  

 (b) Write a chemical equation for the reaction occurring in the combustion tube.

8.  The set-up below was used to investigate electrolysis of a certain molten compound;-

 

Image From EcoleBooks.com

 

 

 

 

 

 

 

 (a) Complete the circuit by drawing the cell in the gap left in the diagram

 (b) Write half-cell equation to show what happens at the cathode  

 (c) Using an arrow show the direction of electron flow in the diagram above

 

9.  Hydrogen can be prepared by reacting zinc with dilute hydrochloric acid.

 a) Write an equation for the reaction.

b) Name an appropriate drying agent for hydrogen gas.

 c) Explain why copper metal cannot be used to prepare hydrogen gas.

 d) Hydrogen burns in oxygen to form an oxide.

  (i) Write an equation for the reaction.  

  (ii) State two precautions that must be taken before the combustion begins and at the end of

the combustion.  

e) Give two uses of hydrogen gas.

f) When zinc is heated to redness in a current of steam, hydrogen gas is obtained. Write an

equation for the reaction.  

g) Element Q reacts with dilute acids but not with cold water. Element R does not react with

dilute acids. Elements S displaces element P from its oxide. P reacts with cold water. Arrange

the four elements in order of their reactivity, starting with the most reactive.

h) Explain how hydrogen is used in the manufacture of margarine.

10.  a) The set-up below is used to investigate the properties of hydrogen.

Image From EcoleBooks.com

 

 

 

 

 

 

 

 

i) On the diagram, indicate what should be done for the reaction to occur

ii) Hydrogen gas is allowed to pass through the tube for some time before it is lit. Explain

iii) Write an equation for the reaction that occurs in the combustion tube

iv) When the reaction is complete, hydrogen gas is passed through the apparatus until they

cool down . Explain  

v) What property of hydrogen is being investigated?

vi) What observation confirms the property stated in (v) above?  

vii) Why is zinc oxide not used to investigate this property of hydrogen gas?

11.  The set up below was used to collect gas K, produced by the reaction between water and

calcium metal.

 

 

Image From EcoleBooks.com

 

 

 

 

 

 (a) Name gas K  ……………………………………………………………..

(b) At the end of the experiment, the solution in the beaker was found to be a weak base. Explain

why the solution is a weak base

 

5. Water and hydrogen Answers

1.  (a) Aluminium is above hydrogen in the reactivity series of elements

 (b) (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)

 

 

 

 

 

2.

 

 

 

 

 

 

 

 

 

3.  a) Calcium chloride

  Drying agent

 

 b) 2H2(g) + O2(g) __________ 2H2O(g)

Image From EcoleBooks.com4.   (i) Steam

  (ii) Mg(s) + H2O(g) MgO(s) + H2(g)

 (iii) Gas P is passed through the combustion tube before heating is commenced

5.  a) 2H2(g) + O2(g) 2H2O(l)
√1  

 b) – Turns anhydrous white paper √½ copper (II) sulphate into blue. √½ Or

  – Turns anhydrous blue √½ cobalt (II) chloride into pink. √½

6.  a)

Image From EcoleBooks.com

Image From EcoleBooks.com

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

b)reverse steam√1

 

 

7.  (a) N

  (b) 4H2O(g) + 3Fe(s) Fe3O4(s) + 4H2(g) (Not balanced 0mk)

 

Image From EcoleBooks.com8.  (a)

 (b) Pb2+ (l) + 2e   Pb(s)

Image From EcoleBooks.com   (c)

 

 

9.  (a) Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g) 1

 (b) Concentrated sulphuric (IV) acid or anhydrous calcium chloride. 1

 (c) Copper cannot displace hydrogen from its solution. 1

 (d) (i) 2H2(g) + O2(g)   2H2O(l) 1

  (ii) Before: Pass hydrogen / through the tube before lighting 1 to drive off air.

End: There should be a continuous flow of hydrogen after / putting off the flame

to avoid an explosion. 1

 
 

 (e) – Filling balloons 1  

  – Manufacture of margarine.

  – Manufacture of ammonia.

  – Conversion of coal to synthetic petrol.

 (f) Zn (s) + H2O(g) ZnO(s) + H2(g) 1  

 (g) S,½ P,  ½ Q,  ½ R, ½

 (h) It adds to unsaturated oils and hardens them. 1

10.  a)  i) Heating of copper (ii) Oxide to be shown on the diagram

ii) To drive out air because mixture of air and hydrogen is explosive when lit  

iii) CuO(g) + H2(g) __________ Cu(g) + H2O(g)

(penalize ½ mark for wrong S.S)

iv) To prevent re-oxidation of hot copper by the atmospheric oxygen

v) Reducing agent

vi) Black copper (ii) Oxide turns to brown showing that copper (ii) Oxide has

been reduced to copper

vii) Zinc is more reactive than hydrogen and therefore cannot be reduced by hydrogen

 

Image From EcoleBooks.com11. (a) Hydrogen gas

(b) – Calcium react with water forming calcium hydroxide solution

Image From EcoleBooks.com – Calcium hydroxide solution dissociates to produce calcium ion (Ca2+ions) and hydroxide

(OH) ions responsible for basic properties.


 




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