12th Chemistry  Revision Exam Question - Answers

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12^TH STANDARD                                      CHEMISTRY

TIME: 3HRS                                                                                                       MARKS: 70

PART-I

CHOOSE THE CORRECT ANSWER:                                                                 15 × 1= 15

1.  𝑆𝑐(𝑍 = 21) is a transition element but 𝑍𝑛(𝑍 = 30) is not because,

a)  Both 𝑆𝑐³⁺ and 𝑍𝑛²⁺ ions are colourlessand form white compounds.

b)  In case of 𝑆𝑐, 3𝑑- orbital are partially filled but in 𝑍𝑛 these are completely filled.

c)  Last electronas assumed to be addedto 4𝑠 level in case of 𝑍𝑛

d)  Both 𝑆𝑐 and 𝑍𝑛 do not exhibitvariable oxidation states

Answer: b)  In case of 𝑆𝑐, 3𝑑- orbital are partially filled but in 𝑍𝑛 these are completely filled.

2.  The stability of +1 oxidation stateincreases in the sequence,

a) 𝐴𝑙 < 𝐺𝑎 < 𝐼𝑛 < 𝑇𝑙                        b) 𝑇𝑙 < 𝐼𝑛 < 𝐺𝑎 < 𝐴𝑙

c) 𝐼𝑛 < 𝑇𝑙 < 𝐺𝑎 < 𝐴𝑙                        d) 𝐺𝑎 < 𝐼𝑛 < 𝐴𝑙 < 𝑇𝑙

Answer:a) 𝐴𝑙 < 𝐺𝑎 < 𝐼𝑛 < 𝑇𝑙  

3.  Solid 𝐶𝑜₂ is an example of,

a)  Covalent solid          b) Metallic solid          c) Molecular solid       d) Ionicsolid

4.  Match items in column-I with the items of column-II and assign the correct code. Column-I                                                Column-II

A)    Cyanide process                    (i) Ultrapure Ge

B)    Froth floatation process        (ii) Extraction of Al

C)    Electrolytic reduction           (iii) Dressingof ZnS

D)    Zone refining                        (iv) Extraction of Au code     A   B          C         D

a)                  i           ii          iii         iv

b)                  iii         iv         ii          i

c)                  iv         iii         ii          i

d)                 ii          iii         i           iv

5.  𝛼 − 𝐷(+) glucose and 𝛽 − 𝐷(+) glucose are,

a)  Epimers                   b) Anomers                 c) Enantiomers            d) Conformational isomers

6.  The product formed, when glycol treatedwith conc 𝐻₂𝑆𝑜₄ is,

a)  1,4 –dioxane           b) 1,2 –epoxy ethane c) Ethene                     d) Ethanal

7.  Which of these is not likely to act as Lewis base?

a) 𝐵𝐹₃                         b) 𝑃𝐹₃                         c) 𝐶𝑂                           d) 𝐹⁻

8.  The 𝑃^𝐻 of 10⁻⁵ 𝑀 𝐾𝑂𝐻 solution will be,

a) 9                              b) 5                              c) 19                            d) 14

9.  Which one of thefollowing is the strongest acid?

a)  2-nitrophenol          b)4-chlorophenol        c) 4-nitrophenol           d) 3-nitrophenol

10.  Williamson synthesisof preparing dimethylether is a/an,

a)  𝑆_𝑁¹ reaction                                               b) 𝑆_𝑁² reaction

c) electrophilic addition                                 d) electrophilic substitution

11.  Acid hydrolysis of inulin produces,

a)  Fructose                 b) Glucose                   c) Maltose                   d) Sucrose

12.  In Froth floatation process, sodium cyanideact as,

a)  Frothing agent       b) Collector                 c) Depressing agent     d) Flux

13.  Which of the following metals has the largestabundance in the earth’s crust?

a)  Aluminium             b)Calcium                   c) Magnesium              d) Sodium

14.  Assertion: 𝐶𝑒⁴⁺ is used as an oxidizing agent in volumetric

analysisReason: 𝐶𝑒⁴⁺ has the tendencyof attaining +3 oxidation state

a)  Both assertion and reason are true and reason is the correctexplanation of assertion

b)  Both assertion and reason are true but reason is not the correct explanation of assertion

c)  Assertion is true but reasonis false

d)  Both assertion and reason are false

15.  The numberof carbon atoms per unit cell of diamond is,

a) 8                            b) 5                              c) 1                              d) 4