Class 10 Science Chapter 4 MCQ

A carbon atom has 4 electrons in its outermost shell, so it requires 4 more electrons to achieve the stable, 8-electron inert gas electron arrangement, which it gets by sharing. Since one carbon atom requires 4 electrons to achieve the eight-electron inert gas structure, therefore, the valency of carbon is 4. That is, carbon is tetravalent (tetra = four; valent = valency).

In saponification reaction, when an ester is heated with sodium hydroxide solution, ester gets hydrolysed (breaks down) to form the parent alcohol and sodium salt of carboxylic acid.

Here, all these statements are correct. Hence, your answer will be option [D].

Because successive members of a homologous series differ by -CH2 unit. You can easily understand by this equation: (C3H8) + (CH2) = C4H10. Thus, C4H10 is the next members of this series. So, homologous series of alkanes is: Methane CH4, Ethane C2H6, Propane C3H8, Butane C4H10. So, C4H8 does not belong to the homologous series. Note: Homologous series is a group of organic compounds having similar structures and similar chemical properties in which a successive compound differs by CH2 group.

Here, all these statements are correct. Hence, your answer will be option [D].

A 5% to 8% solution of Acetic acid in water is called vinegar.

When a small piece of sodium reacts with ethanol, a colourless solution of sodium ethoxide, CH3CH2ONa is obtained. It also gives off bubbles of hydrogen gas. Sodium ethoxide is known as an alkoxide. You can easily understand by this equation: C2H5OH + 2Na → 2C2H5O-Na+ + H2

Pentane has 16 covalent bonds.

The property of carbon element due to which its atoms can join with one another to form long carbon chains is called catenation. So, it is the property of “catenation” of carbon element which is responsible for a very large number of organic compounds (catenation means “self-linking”).

The general formula of saturated hydrocarbons or alkanes is CnH2n + 2 where n is the number of carbon atoms in one molecule of the alkane. You can easily understand by this example: Example: If an alkane has 2 carbon atoms in its molecule, then n = 2, and its molecular formula will be C2H2×2+2 or C2H6

The general formula of alkynes is CnH2n – 2 where n is the number of carbon atoms in one molecule of the alkyne. You can easily understand by this example: Example, If an alkyne has 3 carbon atoms in its molecule, then n = 3, and its molecular formula will be C3H2×3–2 or C3H4.

The unsaturated hydrocarbons (having double bonds or triple bonds between the carbon atoms) are more reactive than saturated hydrocarbons. In other words, alkenes and alkynes are chemically more reactive than alkanes.

A soap molecule is made up of two parts: a long hydrocarbon part and a short ionic part -COO-Na+ group. The long hydrocarbon chain is hydrophobic (water repelling) and ionic portion is hydrophilic (water attracting).

Here, all these statements are correct. Hence, your answer will be option [D].

Oils are unsaturated compounds containing double bonds. Addition reaction are characteristic property of unsaturated hydrocarbons. The given reaction is an example of addition reaction. You can easily understand by this: Edible oils + H2 + Ni or Pd + Heat → Fats (ghee)

Here, all the statements are correct. Hence, your answer will be option [D].

KMnO4 acts as oxidizing agent because it removes hydrogen from CH3CH2OH and adds one oxygen to it. Note: Oxidizing agent is a substance which gives oxygen to the compound for oxidation (i.e. oxygen is removed from it) or which removes hydrogen from the compound. In other words, we can say that CH3CH2OH is oxidised to CH3COOH in the presence of oxidising agent like KMnO4.

Buckminsterfullerene is an allotrope of carbon containing clusters of 60 carbon atoms joined together to form a spherical molecule. Its formula is C60. It is a dark solid at room temperature and as compared to another allotrope from of carbon (as diamond and graphite), it is neither very hard nor soft.

It is the characteristics of a “Homologous Series” is that all the members of a homologous series can be represented by the same general formula. For example, all the members of the alkane series can be represented by the general formula CnH2n+2.

It is the characteristics of a Homologous Series is that the difference in the molecular masses of any two adjacent homologous is 14 u. For example, the molecular mass of methane (CH4) is 16 u, and that of its next higher homologue ethane (C2H6) is 30 u. So, the difference in the molecular masses of ethane and methane is 30 – 16 = 14 u.

Carbon mainly forms covalent compounds, which due to the absence of free ions, are generally poor conductors of electricity. Also, the forces of attraction in between their molecules are weak. Note: Atomic number of carbon is 6. So, its electronic configuration is 2, 4. It can achieve the inert gas electron arrangement only by the sharing of electrons.

The carbon compounds (or organic compounds) containing carboxylic acid group (—COOH group) are called carboxylic acids. Carboxylic acids are commonly known as organic acids. Another name for carboxylic acids is alkanoic acids. The carboxylic acids or organic acids are made up of three elements: carbon, hydrogen and oxygen. The simplest carboxylic acid (or organic acid) is formic acid, HCOOH, which is also known as “Methanoic acid”.

Carbon exist in the atmosphere in the form of carbon dioxide gas (CO2) in air (only 0.03%). Carbon also occurs in the earth’s crust in the form of minerals like carbonates. It also occurs in the form of fossil fuels, organic compounds, wood, cotton and wool etc.

Here, all these statements are correct. Hence, your answer will be option [D].

Here, 14 u, will be the differences in the molecular formulae and molecular masses in all these statements. Hence, your answer will be option [D]. You can easily understand by this: In option [A]: The difference in the molecular formulae of CH3OH and C2H5OH is CH2. The difference in the molecular masses of CH3OH and C2H5OH is 46 – 32 = 14 u. In option [B]: The difference in the molecular formulae of C2H5OH and C3H7OH is CH2. And the difference in the molecular masses of C2H5OH and C3H7OH is 60 – 46 = 14 u. In option [C]: The difference in the molecular formulae of C3H7OH and C4H9OH is CH2. And the difference in the molecular masses of C3H7OH and C4H9OH is 74 – 60 = 14 u.