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.

The covalent bonds between the various carbon atoms are very strong and do not break easily. The reason for the formation of strong bonds by the carbon atoms is their small size. Due to the small size of carbon atoms, their nuclei hold the shared pairs of electrons between atoms strongly, leading to the formation of strong covalent bonds.

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

Functional group present in CH3 – CH2 – CHO is aldehyde. It is propanal containing 3 carbon atom in which “propane” represents 3 carbon atoms while “al” represents aldehyde group. So, propane + al = propanal.

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].

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

A “spherical aggregate of soap molecules” in a soap solution in water is called a “micelle”. In a soap micelle, the soap molecules are arranged readily with hydrocarbon ends directed towards the centre and ionic ends directed outwards.

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

Chlorine reacts with saturated hydrocarbons at room temperature in the presence of Sunlight to form alkyl chloride by displacement reaction.

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.

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.

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.

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.

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

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.