Saturday, May 14, 2011

Sample of Essay Question

Form 4 Chapter 5:


1

Table 11 shows the proton number of atoms P, Q and R.


Element
P
Q
R
Proton number
8
12
17

a)
Based on electron arrangement, explain the formation of chemical bond between

i)
element P and element P                                                      [5 marks ]




ii)
element Q and element R                                                     [7 marks ]




b)
Gas P reacts with element Q to produce a white solid.

i)
Write a chemical equation for the reaction between gas P and element Q.




ii)
State three physical properties of the white solid.              [ 4 marks] ]




c)
What is the position of element Q in the Periodic Table of the elements?
Explain how you obtain your answer.                                  [ 4 marks ]



Suggested Answer:



1
a)i
1.   Two atoms of P combine through covalent bond.                           
2.   Each atom of P needs two more electrons to achieve octet electron arrangement.
3.   Each atom of P contributes two electrons to each other for sharing.              
4.   Two atoms of P share two pairs of electrons.
5.   A double covalent bond is formed.



ii)
1.    Atom Q and atom R combine through ionic bond
2.    To achieve octet electron arrangement,                                         
3.    atom Q with 6 valence electrons loses two electrons to form Q2+ ion             
4.    Two atom R, each atom with 7 valence electrons gain one electron to form R- ion.                                                                      
5.   Q2+ ion and R- ion are attracted to each other by strong electrostatic force.1  
Diagram                                                              







b)i
2Q   +   P2      -->       2QP

ii)
Have high melting point
Usually soluble in water                                                                           
Conduct electricity in the molten state or aqueous solution.  


c)
1.    Element Q is located in Group 2                                                      
2.    because it has two valence electrons                                           
3.    Element Q is located in Period 3                                                      
4.    because it has three shells occupied with electrons                     

3 comments:

  1. Would you just give the answers, please? I'm trying to write an essay here. Thank you.

    ReplyDelete