Introduction to Organic Chemistry questions

All of the following are true about the first organic compound prepared in the laboratory, except that it ..........

1. A contains the element nitrogen.
2. B can be prepared from an inorganic compound.
3. C is formed naturally in the bodies of animals.
4. D does not dissolve in water.

The vital force theory failed because of the compound ..........

1. A NH₄CNO
2. B (NH₂)₂CO
3. C NH₄SCN
4. D (NH₄)₂CO

Organic chemistry is concerned with the study of the compounds of ..........

1. A hydrogen.
2. B sulphur.
3. C oxygen.
4. D carbon.

After urea was prepared, organic compounds were classified according to ..........

1. A their source.
2. B their structure.
3. C their physical state.
4. D the number of carbon atoms in them.

Paraffin wax and acetone can be distinguished by ..........

1. A electrical conductivity.
2. B the products of combustion.
3. C dissolving in benzene.
4. D the physical state.

All of the following are properties of organic compounds, except that ..........

1. A most of them are weakly ionized.
2. B their reactions are slow.
3. C all of them can be polymerized.
4. D all of them contain covalent bonds.

The complete combustion of dimethyl ether gives ..........

1. A C₂H₅OH
2. B H₂O + CO₂
3. C C₂H₄
4. D C₂H₂

Ethyl alcohol is similar to sodium chloride salt in ..........

1. A the physical state.
2. B the reaction with sodium metal.
3. C the type of bonds in the molecule.
4. D dissolving in water.

Most organic compounds are characterized by ..........

1. A a low melting point.
2. B a high boiling point.
3. C solubility in water.
4. D their aqueous solutions conducting electricity.

The following table shows some points of comparison between the two compounds (A) and (B), which have close molar masses:
(A): covalent, gas, insoluble in water, flammable.
(B): ionic, solid, soluble in water, non-flammable.
What is the name of each of the compounds (A) and (B)?

1. A (A): naphthalene, (B): sodium chloride.
2. B (A): butane, (B): sodium chloride.
3. C (A): carbon dioxide, (B): paraffin wax.
4. D (A): ethyl alcohol, (B): paraffin wax.

All of the following are correct, except ..........

1. A A
2. B B
3. C C
4. D D

The two opposite models represent the molecule XY₂ and the molecule Z₂Y
Which model represents the molecule formed by the combination of the two elements (X) and (Z)?

1. A A
2. B B
3. C C
4. D D

The hydrogen atoms are not shown in the molecule of the opposite organic compound.
What is the number of hydrogen atoms in this molecule, and what is the type of this compound?

1. A 7 / saturated homocyclic.
2. B 8 / saturated heterocyclic.
3. C 8 / saturated homocyclic.
4. D 7 / saturated heterocyclic.

Which of the following pairs of compounds are isomers?

1. A C₆H₆ , C₂H₂
2. B C₃H₈ , C₂H₆
3. C C₂H₅OH , CH₃OH
4. D CH₃COOH , HCOOCH₃

The following compounds are isomers of one molecular formula, except ..........

1. A A
2. B B
3. C C
4. D D

From the following structural formulas:
Which of the following are isomers of each other?

1. A (1) , (2).
2. B (3) , (4).
3. C (1) , (2) , (3).
4. D (1) , (2) , (4).

Each of the following is an isomer of one molecular formula, except ..........

1. A A
2. B B
3. C C
4. D D

Which pair of the following hydrocarbons are isomers of each other?

1. A (1) , (2).
2. B (1) , (4).
3. C (2) , (3).
4. D (2) , (4).

What is the molecular formula of the opposite compound?

1. A C₆H₄N
2. B C₆H₆N
3. C C₁₂H₈N₂
4. D C₁₂H₁₂N₂

What is the molecular formula of the opposite compound?

1. A C₈H₁₀
2. B C₈H₁₂
3. C C₈H₁₄
4. D C₈H₁₆

Two isomers with the molecular formula C₂H₆O can be distinguished by using ..........

1. A anhydrous copper sulphate.
2. B sodium bicarbonate.
3. C potassium metal.
4. D calcium hydroxide solution.

Water and pure ethyl alcohol can be distinguished by using ..........

1. A anhydrous CuSO₄(s).
2. B CuSO₄(aq)
3. C Ca(OH)₂(aq)
4. D CaCO₃(s)

When steam is passed over iron filings heated to redness, and then the gas produced is passed over copper(II) oxide powder heated to redness, all of the following substances are formed, except ..........

1. A copper.
2. B magnetic iron oxide.
3. C oxygen.
4. D water vapour.

The compound XSO₄ is used as a fungicide in the purification of drinking water.
What is the role of the compound XO in the experiment for detecting the elements of aromatic benzene?

1. A detecting H₂O(v) only.
2. B detecting CO₂(g) only.
3. C a reducing agent.
4. D an oxidizing agent.

The element produced in the experiment for detecting the elements of a hydrocarbon compound can be identified by using ..........

1. A Ca(OH)₂(aq)
2. B CuSO₄(s)
3. C HNO₃(l)
4. D (NH₄)₂CO₃(aq)

Which of the following may describe the arrangement of carbon atoms in the compounds whose chemical formula is C₅H₁₂?

1. A continuous chain ✗ , branched chain ✗ , cyclic ✓
2. B continuous chain ✓ , branched chain ✗ , cyclic ✓
3. C continuous chain ✗ , branched chain ✓ , cyclic ✗
4. D continuous chain ✓ , branched chain ✓ , cyclic ✗

Which of the following formulas represents an alkane?

1. A C₆H₁₂
2. B C₄H₁₀
3. C C₄H₆
4. D C₆H₆

The structural formula of the compound C₃H₄ includes .......... covalent bonds.

1. A single only.
2. B triple only.
3. C double and triple.
4. D single and triple.

The molecular formula C₅H₁₀ represents a(n) .......... compound.

1. A aliphatic
2. B aromatic
3. C unsaturated cyclic
4. D acetylene (alkyne)

The molecular formula C₄H₈ has two open-chain isomers which include .......... covalent bonds.

1. A single only.
2. B double only.
3. C single and double.
4. D single and triple.

Each of the following describes a compound whose molecular formula is C₃H₄, except ..........

1. A it belongs to the alkyne series.
2. B its molecule contains two pi bonds.
3. C it is called propyne.
4. D it follows the general formula CₙH₂ₙ

Each of the following describes the molecular formula C₃H₆, except ..........

1. A it follows the general formula CₙH₂ₙ
2. B it is a saturated cyclic compound.
3. C it contains the bond (=).
4. D it is an aromatic cyclic compound.

The classifications of the following compounds are all correct, except ..........

1. A A
2. B B
3. C C
4. D D

Which of the following chemical formulas represents a saturated heterocyclic compound?

1. A C₅H₅N
2. B C₅H₁₁N
3. C C₅H₉N
4. D C₅H₇N

Cyclohexane differs from aromatic benzene in ..........

1. A the number of carbon atoms only.
2. B the number of hydrogen atoms only.
3. C the number of carbon atoms and the molecular formula.
4. D the number of hydrogen atoms and the molecular formula.

Naphthalene is one of the .......... compounds.

1. A saturated aliphatic
2. B unsaturated aliphatic
3. C saturated cyclic
4. D unsaturated cyclic

Each of the following describes the compound whose molecular formula is C₆H₆, except that it is ..........

1. A aromatic.
2. B homocyclic.
3. C unsaturated.
4. D odourless.

The two opposite compounds are hydrocarbons. Compare them in terms of:
(1) the type of compound.
(2) the molecular formula.

The two opposite compounds are hydrocarbons. Compare them in terms of:
(1) the general formula.
(2) the type of hydrocarbon.

Rewrite the structural formula of each of the following two compounds correctly, without changing their molecular formulas.

The compound CO(NH₂)₂ is known as carbamide:
(1) What is the other name of this compound?
(2) Is this compound organic or inorganic? Write the equation of its preparation.

Write the structural formula and the molecular formula of each of:
(1) the saturated aliphatic hydrocarbon whose continuous chain is made of 3 carbon atoms.
(2) the saturated aliphatic hydrocarbon whose ring is made of 3 carbon atoms.

The opposite figure shows an experiment carried out on a piece of cloth:
(1) Why was a piece of cloth used in this experiment?
(2) What change takes place in the colour of substance (X) at the end of the experiment? Write the electron configuration of the cation in it.

Deduce the molecular formula and one structural formula of an alkyne whose molar mass is 54 g/mol
[C = 12 , H = 1]

An alkane has a molar mass of 72 g/mol:
(1) Deduce the molecular formula of this alkane.
(2) Draw three different isomers that have the same molecular formula as this alkane.
[C = 12 , H = 1]

Do the two isomers CH₃OC₂H₅ and C₃H₇OH have the same boiling point? Explain.

Which of the following is the number of open-chain aliphatic isomers of the formula C₄H₁₀O that do not react with sodium metal? (Sample exam 2026)

1. A 3
2. B 4
3. C 5
4. D 7