Q17 of 216 Page 461

i) Write a chemical equation of each of the following types of chemical reactions of organic compounds.

a. Oxidation reaction


b. Addition reaction


c. Substitution reaction


ii) What is ethanol? What happens when it is heated with excess conc. H2SO4 at 443 K? Write the role of conc. H2SO4 in this reaction.

i) a. Oxidation reaction:


Carbon compounds can be easily oxidised on combustion. This is called an oxidation reaction. A chemical equation for a reaction in which alcohol (ethanol) is converted to carboxylic acid (acetic acid):



b. Addition reaction:


When unsaturated hydrocarbons add hydrogen in the presence of catalyses such as palladium or nickel to give saturated hydrocarbons. This process is called an addition reaction.


Industrial application: The above reaction is used in the hydrogenation of vegetable oils using a nickel catalyst. Vegetable oils generally have long unsaturated carbon chains.



c) Substitution reaction:


A reaction in which one type of atom or a group of atoms takes the place of another. Example: In the presence of sunlight, chlorine is added to hydrocarbons in a very fast reaction. Chlorine can replace the hydrogen atoms one by one. The chemical reaction is given as:


CH4 + Cl2→ CH3Cl + HCl (in the presence of sunlight)


ii) Ethanol is an organic compound. It is a liquid at room temperature. Ethanol is commonly called alcohol. It is also used in medicines such as tincture iodine, cough syrups, and many tonics. Ethanol is also soluble in water in all proportions. Consumption of small quantities of dilute ethanol causes drunkenness.


When ethanol is heated at 443K with an excess of concentrated sulphuric acid, it gives an unsaturated hydrocarbon. The ethanol gets dehydrated to form ethane. The reaction is given as:


CH3—CH2OH + Hot conc. H2SO4→ CH2=CH2


Ethanol Ethene


The concentrated sulphuric acid can be regarded as a dehydrating agent which removes water from ethanol.


More from this chapter

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15

Two resistors, with resistances 5Ω and 10Ω respectively are to be connected to a battery of emf 6V so as to obtain:

Minimum current flowing


Maximum current flowing


i) How will you connect the resistances in each case?


ii) Calculate the strength of the total current in the circuit in the two cases.

 16

Account for the following:

i) Melting and boiling points of ionic compounds are high.


ii) Aluminium is more active than iron, yet there is less corrosion of aluminium when both are exposed to air.


iii) Solder is used for welding electrical wires together.


iv) A sulphide ore is converted into its oxide to extract the metal.


v) Tarnished copper vessels are cleaned with tamarind juice.

 18

i) Name the plant growth hormone which is synthesized at the shoot tip. Explain briefly why does a plant shoot bend towards light during its growth.

ii) With the help of a schematic diagram, trace the sequence of events occurring, when you step on a sharp object. Name this action.


OR


i) Compare and contrast nervous and hormonal mechanism for control and coordination in animals.


ii) a. Draw a diagram of the human brain.


b. The label on it cerebrum, cerebellum.


c. What is the role of the cerebellum?

 19

i) What is a magnetic field? How can the direction of magnetic field lines at a place be determined?

ii) State the rule for the direction of the magnetic field produced around a current carrying conductor. Sketch the pattern of field lines due to a current flowing through a straight conductor.


OR


i) What is a solenoid? Sketch the pattern of field lines of the magnetic field through and around a current carrying solenoid.


ii) Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the direction of the magnetic field inside and outside the loop.