Class 10 Science Chapter 4 MCQ

The general formula of alkyne is CnH2n-2 where, n is the number of carbon atoms. The first member of Alkyne homologous series is ethyne C2H2.

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).

Atoms other than C and H, if present in organic compound, are called heteroatoms.

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.

A carbon atom has 4 valence electrons in it. Now, in a diamond crystal, each carbon atom is linked to four other carbon atoms by covalent bonds, and hence all the 4 valence electrons of each carbon atom are used up in forming the bonds. Since there are ‘no free electrons’ in a diamond crystal, it does not conduct electricity.

Mineral acids are strong acids which ionise almost completely and carboxylic acids are weak acids which ionise only partially.

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

Though oxides of carbon (like carbon monoxide and carbon dioxide), carbonates, hydrogen carbonates and carbides are also carbon compounds but they are not considered to be organic compounds. This is because their properties are very different from those of the common organic compounds.

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”).

A hydrocarbon in which the two carbon atoms are connected by a “double bond” or a “triple Bond” is called an unsaturated hydrocarbon. Propene, CH3CH = CH2 and Propyne CH3 –C ≡ CH both have double and triple bonds, respectively hence unsaturated. Propane and chloropropane are saturated hydrocarbons which contain only single bonds.

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.

Butanol, CH3 – CH2 – CH2 – CH2 – OH. The alcohols are organic compounds. They all contain the functional group –OH. This group possess the properties of alcohols. The names of alcohols end with -ol – e.g., ethanol, butanol.

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)

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.

A molecule of ammonia (NH3) has only single bonds and these are covalent bonds. Note: Atomic number of N is 7. Its electronic configuration is 2, 5 so it needs 3 more electrons to complete its “Octet”. It gains 3 electrons each from 3 hydrogen atoms. Also, N has one lone pair of electrons. The pair of electrons on the nitrogen atom in NH3 molecule which is not involved in bond formation is called lone pair.

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.

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.

The common name of pentanone is methyl propyl ketone.

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.