Practical Organic Chemistry Test

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Practical Organic Chemistry Test - 2

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Weekly Quiz Competition

Question 1
1 / -0

For which compound, Lassaigne’s test for nitrogen is positive.

A
H₂NCONH₂

B
all the three

C
NH2OH

D
NH₂NH₂

Solution

Hydroxylamine and hydrazine, both do not have carbon, hence NaCN will not be formed in Lassaigne’s extract leading to negative test for nitrogen.
Question 2
1 / -0

Statement-1 : Lithium is not used in Lassaigne’s test.
Statement-2 : It generally forms covalent compounds.

A
Both Statement-1 and Statement-2 are true and Statement-2 is the correct explanations of Statement-1.

B
Both Statement-1 and Statement-2 are true and Statement-2 is not the correct explanation of Statement-1.

C
Statement-1 is true but Statement-2 is false.

D
Statement-1 is false but Statement-2 is true.

Solution

Reason is the correct explanation of Assertion.
Question 3
1 / -0

Sometimes diazo compounds do not respond Lassaigne’s test for nitrogen because

A
These are quite stable compounds and do not decompose to elemental nitrogen

B
These form organo metallic compounds with sodium

C
Their nitrogen contents is removed, during heating in the form of nitrogen gas

D
These contain very little carbon

Solution

Since diazo compounds may lose nitrogen in the form of nitrogen gas, they sometimes do not respond Lassaigne’s test for nitrogen.
Question 4
1 / -0

The compound which gives white precipitate on heating with HNO₂ followed by addition of silver nitrate, is

A
(C₂H₅)₃NHCI

B
2,4,6-Trinitrochlorobenzene

C
None of these

D
Both (a) and (b)

Solution

(C₂H₅)₃N₊HCI⁻ is an ionic compound, so it will form precipitate of AgCI on adding AgNO³. In 2, 4, 6-trinitrochlorobenzene, - CI is activated due to the presence of three - NO₂ groups in o- and p-positions, so it will be very reactive leading to formation of AgCI on adding HNO₃ and AgNO₃.
Question 5
1 / -0

Lassaigne’s extract of p-nitrochlorobenzene is acidified with dil. HNO₃ and then treated with silver nitrate solution, the white precipitate formed is due to

A
no white ppt. is obtained

B
AgCN

C
both (a) and (b)

D
AgCI

Solution

Lassaigne’s extract for the compound p-nitrochlorobenzene contains both NaCN as well as NaCI, so on treatment with AgNO₃, the extract give precipitate of AgCN as well as AgCI unless it is boiled with HNO₃ which will remove NaCN as gaseous HCN.
Question 6
1 / -0

Statement-1 : Formic acid usually exists as a dimer but hydrogen fluoride exists as a polymer.
Statement-2 : In case of formic acid, an intramolecular hydrogen bond is present, but in case of HF, intermolecular hydrogen bond is present.

A
Both Statement-1 and Statement-2 are true and Statement-2 is the correct explanations of Statement-1.

B
Both Statement-1 and Statement-2 are true and Statement-2 is not the correct explanation of Statement-1.

C
Statement-1 is true but Statement-2 is false.

D
Statement-1 is false but Statement-2 is true.

Solution

Formic acid being a bent molecule forms a cyclic dimer while HF being a liner molecule form a polymer by H- bonding.
Question 7
1 / -0

Statement-1 : Fehling's solution can be used to distinguish benzaldehyde from acetaldehyde.

Statement-2 : The C-H bond of CHO group in benzaldehyde is stronger than the C-H bond of CHO group in acetaldehyde.

A
Both Statement-1 and Statement-2 are true and Statement-2 is the correct explanations of Statement-1.

B
Both Statement-1 and Statement-2 are true and Statement-2 is not the correct explanation of Statement-1.

C
Statement-1 is true but Statement-2 is false.

D
Statement-1 is false but Statement-2 is true.

Solution

Reason is the correct explanation of Assertion.
Question 8
1 / -0

Carius method is not reliable for the estimation of

A
Br

B
S

C
Cl

D
I

Solution

Silver iodide is somewhat soluble in nitric acid.
Question 9
1 / -0

Positive Beilstein test for halogens show that

A
None of these

B
A halogen may be present

C
A halogen is absent

D
A halogen is definitely present

Solution

A positive Beilstein’s test for halogens does not always indicate the presence of halogen since some halogen free compound viz. urea, thiourea, amides etc. also respond this test. The reason being the fact that these halogen free compounds from cuprous cyanide which is volatile and decomposes to copper which burns with green flame.

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Re-Attempt Weekly Quiz Competition

Practical Organic Chemistry Test - 2

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Practical Organic Chemistry Test - 2

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Question 1

H2NCONH2

all the three

NH2OH

NH2NH2

Solution

Question 2

Both Statement-1 and Statement-2 are true and Statement-2 is the correct explanations of Statement-1.

Both Statement-1 and Statement-2 are true and Statement-2 is not the correct explanation of Statement-1.

Statement-1 is true but Statement-2 is false.

Statement-1 is false but Statement-2 is true.

Solution

Question 3

These are quite stable compounds and do not decompose to elemental nitrogen

These form organo metallic compounds with sodium

Their nitrogen contents is removed, during heating in the form of nitrogen gas

These contain very little carbon

Solution

Question 4

(C2H5)3NHCI

2,4,6-Trinitrochlorobenzene

None of these

Both (a) and (b)

Solution

Question 5

no white ppt. is obtained

AgCN

both (a) and (b)

AgCI

Solution

Question 6

Both Statement-1 and Statement-2 are true and Statement-2 is the correct explanations of Statement-1.

Both Statement-1 and Statement-2 are true and Statement-2 is not the correct explanation of Statement-1.

Statement-1 is true but Statement-2 is false.

Statement-1 is false but Statement-2 is true.

Solution

Question 7

Both Statement-1 and Statement-2 are true and Statement-2 is the correct explanations of Statement-1.

Both Statement-1 and Statement-2 are true and Statement-2 is not the correct explanation of Statement-1.

Statement-1 is true but Statement-2 is false.

Statement-1 is false but Statement-2 is true.

Solution

Question 8

Br

S

Cl

I

Solution

Question 9

None of these

A halogen may be present

A halogen is absent

A halogen is definitely present

Solution

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H₂NCONH₂

NH₂NH₂

(C₂H₅)₃NHCI