Class 10 Science Chapter 4 MCQ

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.

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.

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.

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.

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.

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.

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”.

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.