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Form 2 Chemistry End of Term 3 Exam 2021

Class: Form 2

Subject: Chemistry

Level: High School

Exam Category: Form 2 End Term 3 Exams

Document Type: Pdf

    

Views: 84     Downloads: 14

Exam Summary


1. Name a method that can be used to separate each of the following substances. (3mks)
a) A mixture of petrol and diesel.


b) Kerosene and water.


c) Food coloring ingredients in a sauce.


2. The table below shoes the formulae of elements P, Q, R and S (not actual symbols) and their chlorides.
imag.PNG
a) State the group in which element Q belongs. (1mrk)


b) Identify one element which is a non-metal. (1mk)


c) Write down the formulae of P oxide. (1mk)


3. Hydrogen can be prepared by passing steam over heated Zinc powder as shown in the diagram
imag1.PNG
a) Write down the chemical reaction that produces hydrogen gas. (1mrk)


b) Explain why hydrogen should be burned if not collected over water. (1mrk)


c) Give another metal that can be used instead of Zinc. (1mrk)


4. A piece of sodium metal was placed in a trough half filled with cold water. State the observations that were made. (3mrks)


5. The curves below represents the variation of temperature with time when pure and impure samples of a solid were heated separately.
imag2.PNG
i. Which curve shows the variation in temperature of the pure solid. Explain (2Mks)


ii. State the effect of impurities in the melting and boiling points of a pure substance. (2Mrks)


6. Air was passed through several reagents as shown below;
imag3.PNG
Name the main inactive component of air (1mk)
b.) Name the components of air that are removed in the following chambers (3mks)
i. Chamber 1


ii. Chamber 3


iii. Chamber 4


c.) What is the purpose of passing air through concentrated Sulphuric (VI) acid? (1mk)


d.)Write a chemical equation for the reaction which takes place in
i. Chamber 1 (1mk)


ii. Chamber 4 (1mk)


e.) Explain the observation made in chamber 3 during the reaction. (2mrks)


f.)Name one gas which escapes from the scheme above. (1mrk)


7.a) Distinguish between hygroscopy and efflorescence. (2mrks)


b.)Starting with lead (II) oxide describe how you would prepare Lead (II) sulphate (3mrks)


8.a) discuss the criteria for testing purity of water. (2mrks)


b.) write the word equations for the reaction between dilute hydrochloric acid and the following. (4mks)
(i) magnesium oxide

(ii) calcium hydrogen carbonate

(ii) zinc metal

(iv) potassium hydroxide


9. a) Using dots and crosses to represent electrons, draw a diagram to show bonding in Sodium Chloride(NaCl) (2mrks)



b.) Both graphite and diamond are allotropes of carbon. Graphite conducts electricity whereas diamond does not. Explain (2mrks)



10. Both ions #Y^(2-)# and #Z^(2+)# have an electron configuration of 2.8.8
a.) Write the electron arrangement for (2mrks)
Y


Z


b.) What is the mass number of atom Z given that it has 20 neutrons (1mrk)



11. The diagram on the next page shows a set up which was used by a student to investigate the effect of electricity on molten Lead (II) Bromide.
imag4.PNG
a.) Explain the observation at the cathode (2mrks)


b.) Why does solid lead (II)Bromide not allow the passage of electricity (2mrks)


c.)Write equations to show the reactions taking place
i. At the cathode (1mrk)


ii. At the anode (1mrk)


12. Study the set up below and answer the questions that follow
imag5.PNG
a.) Identify gas X (1mrk)


b.) Write a chemical equation for the reaction liberating gas X (1mrk)


c.) Why is it not advisable to use calcium in this method of preparing gas X? (2mrks)


d.) Give the use of anhydrous calcium chloride in the U-tube (1mrk)


e.) Name another substance that could serve the same purpose as anhydrous calcium chloride (1mrk)


f.) Name the method used to collect gas X (1mrk)


13. The grid below shows part of the periodic table. Use it to answer the questions that follow.
imag6.PNG
a.) Which of the elements has the largest atomic radius? Explain (2mrks)


b.) Identify the most reactive metal. Explain (2mrks)


c.) Name the chemical family to which P and Q belong. (1mrk)


d.) Compare the atomic radius of S and U. Explain (2mrks)


e.) Select an element that does not form an ion. Explain (2mrks)


f.) Give the formula of one stable cation with an electron arrangement of 2.8.8 (1mrk)


14.a) Define the term isotope (1mrk)


b.)Chlorine gas has a relative atomic mass of 35.5. It is made up of two isotopes imag7.PNG and imag8.PNG. Determine the relative abundance of each isotope in the chlorine gas. (3mrks)


15. Write a balanced equation for the decomposition of the following solids (3mrks)
a. #PbCO_(3(s)# #rarr# HEAT


b. #Na_2CO_3. 10H_2O_((s)# #rarr# HEAT


c. #KNO_(3(s)# #rarr# HEAT


16. Though Sodium and aluminium are in the same period and are both metals, aluminium is a better conductor of electricity. Explain (2mrks)


17.(a) List any three uses of oxygen gas` (3mrks)


(b) State the conditions necessary for rusting. (2Mrks)

 

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