Class XII_Delhi_Chemistry_Set-1
General Instructions:
(i)
All questions are compulsory
(ii)
Question numbers 1 to 8 are very short-answer questions and carry 1 mark each.
(iii) Question numbers 9 to 18 are short-answer questions and carry 2 marks each.
(iv)
Question numbers 19 to 27 are also short-answer questions and carry 3 marks.
(v)
Question numbers 28 to 30 are long-answer questions and carry 5 marks each.
(vi)
Use Log Tables, if necessary. Use of calculators is not allowed.
1.
How many atoms constitute one unit cell of a face-centered cubic crystal?
1
Ans.
Number of atoms in one face centered cubic unit cell can be determined from the number
1
of atoms contributed from the faces and the corners of the unit cell as: (8 corners ×
8
1
1
1
atom per corner = 8  = 1 atom) + (6 faces ×
atom per unit face = 6  = 3 atoms).
2
2
8
 Total no. of atoms per unit cell = 4 atoms.
2.
Name the method used for the refining of Nickel metal.
Ans.
Method used for refining of nickel metal is Mond’s process. In this process nickel is
heated in a steam of carbon monoxide, which yields in the formation of nickel carbonyl.
Nickel carbonyl on further heating decomposes to five pure nickel.
330-350K
Ni  4CO 
 Ni  CO 4
1
450-470K
Ni  CO 4 
 Ni  4CO
3.
What is the covalency of nitrogen in N2O5?
Ans.
In N2O5, the covalency of N is restricted to 4 due to sp2 hybridisation of nitrogen atom
involving one 2s and three 2p orbitals.
4.
Write the IUPAC name of CH3  CH  CH 2  CH = CH 2
|
Cl
Ans.
IUPAC Name: 4-Chloropent-1-ene
1
1
Class XII_Delhi_Chemistry_Set-1
5.
What happens when CH3 – Br is treated with KCN?
Ans.
It is a nucleophilic substitution reaction. The nucleophile CN  substitutes Br  . The
reaction is as follows: CH3Br + KCN  CH3CN + HBr
6.
Write the structure of 3-methyl butanal.
Ans.
H3C — CH — CH 2 — CHO
The structure of 3-Methyl butanal is
|
CH3
7.
Arrange the following in increasing order of their basic strength in aqueous solution:
CH3.NH2, (CH3)3N, (CH3)2NH
Ans.
(CH3)3N,CH3NH2, (CH3)2NH
8.
What are three types of RNA molecules which perform different functions?
Ans.
There are three different types of RNA molecules: Messenger RNA (mRNA), Transfer
RNA (tRNA) and Ribosomal RNA (rRNA)
1
1
1
1