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Assignment 2
A form one class carried out an experiment to determine the active part of air. The diagram below shows the set-up of the experiment and also the observation made.
(a)
(i) Identify substance M ..................................................................................
(ii) State two reasons for the suitability of substance M for this experiment
(b) Write the equation for the reaction of substance M and the active part of air
(c)
(i) Using the letters Y and X write an expression for the percentage of the active part of air
(ii) The expression in (c)(i) above gives lower value than the expected. Explain (d) (i) Explain the observation made when litmus paper is dipped into the beaker at the end of the experiment (ii) Name the active part of air ................................................................................................
(iii) Suggest another method that can be used to determine the active part of air 15. A piece of phosphorous was burnt in excess air. The product obtained was shaken with a small amount of hot water to make a solution i) Write an equation for the burning of phosphorus in excess air ii) The solution obtained in (b) above as found to have pH of 2. Give reasons for this observation
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
2. In an experiment, dry hydrogen gas was passed over hot copper (II) oxide in a combustion
tube as shown in the diagram below:-
(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
Study the diagram below:
(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.
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.
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?
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