Chemistry Grade 12

Chemistry Past Papers 12th Class Gujranwala Board

Section A-(MCQs)

i) The newspaper can be recycled again as many time as:                (Mark 1)

A. 5
B. 3
C. 4
D. 2
Answer:
A. 5

Section B-(Short Questions)

Q.2 i) "Ionization energy increases from left to right in a period.” Justify the statement.                                                                                                            (Marks 2)

Answer:
As we move from left to right in a period, the outer shell remains the same, while the nuclear charge increases effectively that makes the removal of an electron difficult and hence the value of ionization energy increases.

Section C-(Long Questions)

Q.5 a) Discuss the position of hydrogen over VII A-Group elements.
                                                                                                                                            (Marks 4)

Answer:
Position of Hydrogen over VII A-Group Elements
Hydrogen has certain similarities with halogens due to this it can be placed above VII A-group elements.
But it also shows certain differences with this group. Therefore, it is difficult to decide its position in the periodic table.
Similarities

  •  

    Hydrogen is a gas like most of halogens.

  •  

    Hydrogen exists in diatomic form (H2) like F2, Cl2, and I2.

  •  

    Hydrogen requires one electron to complete its outermost shell just like halogens.

  •  

    Both hydrogen and halogens form stable ionic compounds with alkali metals.

  •  

    Hydrogen forms H- ion by gaining one electron like F-, Cl-, Br-, etc.

Differences

  •  

    Hydride ion H- is unstable in aqueous solution while halides ions, i.e,. F-, Cl-, Br- etc, are stable.
    H-    +    H2O   →    H2   +   OH-

  •  

    Hydrogen has just one electron in its outermost shell while halogens have seven electrons in their outermost shells.

  •  

    Hydrogen forms very stable compound H2O with oxygen while halogens do not form.

  •  

    Alkali metal hydrides e.g. NaH are mostly basic while alkali metals halides e.g. NaCl are neutral.

  •  

    Hydrogen can form H+ ion by losing an electron, while halogens do not form positive ions.

Signup now!

ready to get started? simply fill out this form to register for our exclusive seven-day free trial!

Free Signup

0320,0321,0322,0323,0324,0325,0300,0301,0302,0303,0304,0305,0306,0307,0308,0309,0330,0331,0332,0333,0334,0335,0336,0337,0340,0341,0342,0343,0344,0345,0346,0347,0348,0349,0310,0311,0312,0313,0314,0315,0316,0318,0355

Take your study material Where you go

you can now review solved past-papers, revise book notes, take quizzes, or stream our video lectures on the go with tutoria app available on iOS and Android.