Chemistry GRE Sample

GAMSAT

| FREE CHEMISTRY SAMPLE QUESTIONS www.prepgenie.com.au

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Unit 1 Questions 1 – 8 An organic compound having a carbon attached to four different groups is optically active. But the opposite is not necessarily true, i.e. not all optically active organic compounds have chiral carbons. Presence or absence of chiral centre is not the sufficient criterion for optical activity. The ultimate criterion is presence or absence of either plane or centre of symmetry. Two compounds which are non- superimposable mirror images of each other are called enantiomers. If a compound contains more than one chiral carbon, new words are required to describe the relationship between various stereoisomers of the compound. Those words are diastereomers and mesomers. 1.

Optically active compounds among the following is A C

2.

(i) and (ii) (i) and (iii)

B D

(ii) and (iii) (iv) and (v)

Which of the following statements is/are correct about two organic compounds which are steroisomers? A B C D

4.

D

CH3CH2 CDCH2 CH3 | Cl CH3CH 2 CHDCH3

B

Which of the following form diastereomeric pair?

A C 3.

CH3CH2 CHCH2 CH3 | Cl CH3CH 2 CHDCH 2 CH3

They must be enantiomers They must be diastereomers They must be constitutional isomers None of the above

There are two organic compounds which are steroisomers of each other. Which of the following statements is incorrect? A B C D

They might be enantiomers They might be mesoiomers They might be diastereomers They might be tautomers

5.

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GAMSAT


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Which of the following statements is/ are correct regarding the above compound?

A B C D 6.

A sample of organic compound(s) is found to have optical rotation of +20 0. Which of the following statements is incorrect about the given sample? A B C D

7.

The sample might be a d-isomer The compound must be containing chiral carbon The sample might be a mixture of d and l isomers in unequal amounts The compound(s) in the sample must be chiral

Optically active compound(s) among the following is/are

A B C D 8.

It is optically inactive due to plane or centre of symmetry. It is optically inactive as it is a non-enantiomer. Being chiral it is optically active It is optically active due to the presence of C2 axis of symmetry.

(i), (ii) and (v) (i), (ii), (iv) and (v) (ii), (iii) and (v) (ii), (iii), (iv) and (v)

Which of the following statements is/are true about the compound (iv) given in the previous question? A B C D

It is optically inactive due to the presence of plane of symmetry. It is optically active due to the presence of centre of symmetry. It is optically active due to the absence of all elements of symmetry. None of the above

Unit 2 Questions 9 – 13 Acidic and basic nature of organic compound depends upon inductive effect. Acidic strength of organic acid increases with increase in electron withdrawing group or –I group and decreases with increase in electron releasing group or +I group. Basic strength of organic compound having just opposite relationship with inductive effect, i.e. basic strength ∞ +I effect ∞ 1/-I effect. The other factor which explains acidic strength is distance of electron withdrawing group. An acid dissociation constant, Ka, (also known as acidity constant, or acid-ionization constant) is a quantitative measure of the strength of an acid in solution. It is the equilibrium constant for a chemical reaction known as dissociation in the context of acid-base reactions. © All rights reserved by Prepgenie.com.au. No parts of this booklet may be produced or utilised in any form without the written permission of Prepgenie.com.au. [For reporting errors or doubts clearance, mail to [email protected]]

GAMSAT


HA  A

9.

10.

H HA

B

C

D

The strongest base is CH3-CH2-OH H2O CH≡CH CH2═CH2

Which of the following acid having highest Ka value? C6H5COOH HCOOH CH3-COOH Cl-CH2-CO-OH

Which of the following is strongest base? A B C D

13.

A

A

A B C D 12.

, Ka

Which one is strong acid among these?

A B C D 11.

H

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(CH3)2NH (CH3)3N CH3-CH2-NH2 Cl-CH3-NH2

In the following compounds maximum acidic character is

A

B

C

D



GAMSAT

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Unit 3 Questions 14 - 15 Following two graphs are based on the conductometric titration (Titration based on changes in the electrical conductance of a solution) of acid-base reaction. The underlying principles of conductometric titration are that the solvent and any molecular species in solution exhibit only negligible conductance; and the conductance of a dilute solution rises as the concentration of ions is increased. It is accepted that in a given concentration, the hydrogen ion and the hydroxyl ion are much better conductors than any of the other ions. Answer the questions given at the end of it.

14.

Select the correct statement: A B C D

15.

Graph A is for weak monobasic acid while graph B is for monobasic strong acid. Graph A is for strong monobasic acid and graph B is for weak dibasic acid. Graph A is for weak monobasic acid and graph B is for weak dibasic acid. Graph A is for strong monobasic acid and graph B is for weak monobasic acid.

In graph B, there is increase in conductance before (though slightly) and after the end point. This is due to: A B C D

Formation of NaCl type salt from strong acid which is hydrolysed releasing NaOH NaCl + H2O ↔ NaOH + HCl Formation of CH3COONa salt from weak acid which is hydrolysed releasing NaOH Ionisation of water Autoprotolysis of water

Unit 4 Questions 16 - 20 Extraction of Aluminium can be understood by:

Bauxite Al2O3.2H2O

Conc. of Ore by chemical method

Pure Alumina Al2O3

Pure Aluminium

Reduction of Alumina by Electrolysis

Aluminium Impure

Electrolysis using suspended graphite rods anode and C-lining inside the Fe-container


GAMSAT


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Electrolytic reduction of Al2O3: At 900°C, Fluorspar (CaF2) is used to make Al2O3 a good conductor of electricity. As cryolite has greater electrochemical stability, it does not dissociate itself but increases the dissociation of Al 2O3. Metallic aluminium is liberated at the cathode. Electrolyte: (Al2O3+Cryolite) Cathode: Graphite inside the Fe contain 16.

The purpose of adding cryolite is: A B C D

17.

Coke powder is spreaded over the molten electrolyte due to: A B C D

18.

To decrease the melting point of electrolyte To increase electrolytic conductivity power To remove the impurities as slag All of the above

The molten electrolytes contain Na+, Al3+, Ca2+ but only Al gets deposited at cathode because: A B C D

20.

Prevent the heat radiation from the surface Prevent the corrosion of graphite anode Prevent oxidation of molten aluminium by air Both (A) and (B)

The function of fluorspar (CaF2) is: A B C D

19.

To increase the electrical conductivity of pure aluminium To lower the melting point of Al2O3 To remove the impurities as slag To increase the Al% in the yield

Standard reduction potential of Al is more than those of Na & Ca. Standard oxidation potential of Al is more than those of Na & Ca. Discharge potential Al3+ is higher than Na+ & Ca2+. Graphite reacts only with Al3+ and not with Na+ & Ca2+.

What is wrong if anode is made of nickel instead of graphite? A B C D

Ni is costly. Anode will be affected by produced Cl2. Graphite remain unaffected by produced Cl2. Ni may be affected by high temperature.

Unit 5 Questions 21 – 25 In organic compounds, coordination compounds often show various types of isomerism. The isomerism can be categorized in two main types: (A) Structural isomerism (B) Stereo or space isomerism Structural isomerism arises due to the difference in structures of coordination compounds while stereo or space isomerism arises on account of the different positions and arrangements of ligands (atoms or groups) in space around the metal ion. Stuctural isomerism can be classified in following types:


GAMSAT

(I) (II) (III) (IV) (V)

21.

Which of the following coordination compounds, exhibits ionization isomerism?

Six Four Three Two

The compounds [Cr(H2O)6]Cl3, [Cr(H2O)5Cl]Cl2.2H2O and [Cr(H2O)4Cl2]Cl.2H2O exhibit A B C D

25.

Hydrate isomerism Linkage isomerism Ionisation isomerism Coordinate isomerism

How many hydrate isomers are possible with the formulae CrCl3.6H2O? A B C D

24.

[Cr(NH3)6]Cl3 [Cr(ox)3]3[Cr(en)3]Cl3 [Cr(NH3)5Br]SO4

The pair [Co(NH3)5NO3]SO4 and [Co(NH3)5SO4]NO3 will exhibit A B C D

23.

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Ionisation isomers- which give different ions in solution, e.g. [CoBr(NH3)5]SO4 and [Co(SO4)(NH3)5]Br. Hydrate isomers- which differ in H2O as ligand or as hydration, e.g. [Cr(H2O)6]Cl3, [CrCl(H2O)5]Cl2.H2O, and [CrCl2(H2O)4]Cl.2H2O. Linkage isomers- which differs in atom linked to metal atom, e.g. [Co(NO2)(NH3)5]2+ and [Co(ONO)(NH3)5]2+. Coordination isomers- which involve interchange of ligands, e.g. [Co(NH3)6][Cr(CN)6] and [Cr(NH3)6][Co(CN)6]. Coordination position isomerism- which arises in the bridged complexes due to the difference in the attachment of ligands with the metal atoms.

A B C D 22.


Linkage isomerism Geometrical isomerism Ionisation isomerism Hydrate isomerism

The total number of possible isomers for the complex compound [Cu(NH3)4][PtCl4] are A B C D

Three Six Five Four

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Chemistry GRE Sample

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