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Write the next homologue of each of the following:
i) C2H4
ii) C4H6
i) C2H4 is an alkene name is an ethene. Its next homologue is obtained by adding a -CH2- unit. Thus the name of next homologue is propene C3H6.
ii) C4H6 is an alkyne; the homologue name is butyne. Its next homologue is obtained by adding -CH2- unit and thus the name homologue next is pentyne
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What are the covalent compounds? why are they different from ionic compounds? List their three characteristic properties.
| Covalent Bonding | Ionic Bonding |
| A covalent compound is formed by the mutual sharing of electrons to complete the octet of the shell. For example, O2 is formed by the covalent bonding. |
In the ionic bonding, the transfer of electron takes place. In this bonding, one electron donor and one electron acceptor are required. For example NaCl. |
 |
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| i) They have low melting. | They have high melting. |
| ii) They do not conduct electricity | They conduct electricity |
| iii) They have definite shape | They do not have a definite shape. |
When ethanol reacts with ethanoic acid in the presence of conc. H2SO4, a substance with fruity smell is produced. Answer the following:
i) State the class of compounds to which the fruity smelling compounds belong. Write the chemical equation for the reaction and write the chemical name of the product formed.
ii) State the role of conc. H2SO4 in the reaction.
i) When ethanol and ethanoic acid react with each other in the presence of concentrated H2SO4 acid, an ester is formed with a fruity smell. The chemical equation for the reaction is given as:
ii) A carboxylic acid is a very weak proton, therefore, the H2SO4 is used to protonate it to be able to react with the acid. However, the reaction is reversible therefore H2SO4 is also used as drying agent to remove water and shift the equilibrium to favour the ester forming.
calcium is an element with atomic number20. Stating reason, answer each of the following questions:
i) Is calcium a metal or a non-metal?
ii) Will its atomic radius be larger or smaller than that of potassium with atomic number 19?
iii) Write the formula of its oxide.
i) The atomic number of calcium is 20. Its electronic configuration is 2,8,8,2. The valency of calcium is +2. Hence it is a metal belong to the group 2.
ii) The radius of calcium is smaller than potassium because both elements lie in the third period of the periodic table. Potassium lies to the left of calcium in the period, and atomic size decreases, going left to right due to increase in the force of attraction by the nucleus.
iii) The oxide of calcium is calcium oxide and its chemical formula is given as CaO.
An element 'M' with electronic configuration (2,8,2) combines separately with (NO3)-, (SO4)2-, and (PO4)3- radicals. Write the formula of the three compounds so formed. To which group and period of the Modern Periodic Table do the element 'M' belong? Will 'M' form covalent or ionic compounds ? Give a reason to justify your answer.
Electronic configuration of M= 2,8,2
Number of valence electron of M=2
valency of M = Number of valence electrons = 2
Valency of the nitrate ion (NO3)- = 1
Valency of the sulphate ion (SO4-2) =2
Valency of phosphate ion (PO4-3) =3
The formulae of nitrate ,sulphate and phosphate formed by M are M(NO3)2, MSO4, and M3(PO4)2 respectively.
Since the valency of M is 2 and the atomic number of M is 12 such as (2,8,2), this element belongs to the group 3 and period 3 of the periodic table.
This element will tend to form an ionic compound by losing two valence electrons to achieve a noble gas electronic configuration, that is a stable octet in the valence shell.
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Mock Test Series
