After reading the chapter and understanding the concepts of topics, it becomes necessary to solve questions on topics of chapter. Therefore, We are giving some "Solved Short Questions on S-Block Elements" to practice and to know your Grasping capacity of concepts for this chapter.
Q.1. Why the elements of second raw (first short period) show a number of differences in properties from other members of their respective families.
Ans.1. The difference in the properties of the first member of a group from those of the other members is due to
(i) Smaller size of the atom
(ii) Presence of one inner shell of only two electrons and
(iii) Absence of d-Orbitals.
Q.2. What is diagonal relationship due to?
Ans.2. Elements having similar size of atoms or ions electronegativity or similar polarizing power show diagonal relationship.
For example, Li and Mg; Be and Al have many similar properties.
Q.3. What is the general name for elements of group 1?
Ans.3. Elements of group 1 are called “Alkali Metals” because their oxides dissolve in water to form hydroxides which are strong bases or alkalies.
Q.4. What are s- block elements?
Ans.4. S-block elements are those in which the last electron enters the outermost s-orbital.
As the s-orbital can accommodate only two electrons, two groups (1 & 2) belong to the s-block of the Periodic Table.
Q.5. Which elements of s- block are largely found in biological fluids & what is its importance?
Ans.5. Monovalent sodium and potassium ions and divalent magnesium and calcium ions are found in large proportions in biological fluids. These ions perform important biological functions such as maintenance of ion balance and nerve impulse conduction.
Q.6. Why alkali metals are highly electropositive & they are not found in free state ?
Ans.6. The loosely held s-electron in the outermost valence shell of these elements makes them the most electropositive metals. They readily lose electron to give monovalent M+ ions. Hence they are never found in free state in nature.
Q.7. Give reason for the colour imparted to the flame by alkali metals
Ans.7. The alkali metals and their salts impart characteristic colour to an oxidizing flame. This is because the heat from the flame excites the outermost orbital electron to a higher energy level. When the excited electron comes back to the ground state, there is emission of radiation in the visible region.
Q.8. What happens when alkali metals react with dihydrogen?
Ans.8. The alkali metals react with dihydrogen at about 673K (lithium at1073K) to form hydrides. All the alkali metal hydrides are ionic solids with high melting points.
2 M + H2 ===> 2M+H-
Q.9. Give reason for the low solubility of LiF & CsI in water.
Ans.9. The low solubility of LiF in water is due to its high lattice enthalpy whereas the low solubility of CsI is due to smaller hydration enthalpy of its two ions. Other halides of lithium are soluble in ethanol, acetone and ethyl acetate; LiCl is soluble in pyridine also.
Q.10. Write any four Uses of washing soda.
Ans.10. i) It is used in water softening, laundering and cleaning.
(ii) It is used in the manufacture of glass, soap, borax and caustic soda.
(iii) It is used in paper, paints and textile industries.
(iv) It is an important laboratory reagent both in qualitative and quantitative analysis.
Q.11. How does the atomic and Ionic Radii of alkaline earth metals vary in comparison to alkali metals
Ans.11. The atomic and ionic radii of the alkaline earth metals are smaller than those of the corresponding alkali metals in the same periods. This is due to the increased nuclear charge in these elements. Within the group, the atomic and ionic radii increase with increase in atomic number.
Q.12. Alkali and alkaline earth metals cannot be obtained by chemical reduction method. Explain.
Ans.12. Since they are themselves stronger reducing agents than majority of the common reducing agents used.
Q.13. Why cannot sodium and potassium be prepared by the electrolysis of their aqueous solutions?
Ans.13. The electrode potential, i.e., reduction potential of Na ( –2.71 V) or K (- 2.92) is much lower than that of H2O (-0.83 V), therefore, upon electrolysis, water gets reduced in preference of Na+ or K+ ions. In other words, sodium and potassium cannot be obtained by electrolytic reduction of Na+ or K+ ions in aqueous solutions.
Q.14. Give reason . the sulphate of Be & Mg are soluble in water .
Ans.14. The sulphates of the alkaline earth metals are all white solids and stable to heat. BeSO4, and MgSO4 are readily soluble in water; the solubility decreases from CaSO4 to BaSO4. The greater hydration enthalpies of Be2+ and Mg2+ ions overcome the lattice enthalpy factor and therefore their sulphates are soluble in water.
Ans.15. The alkaline earth metals readily react with acids liberating dihydrogen gas.
M + 2HCl → MCl2 + H2
This was the 1st part of "Solved Short Questions on S-Block Elements (Chapter 10)". Check out more post from below "Related Post" Section and other chapter's help on right hand side. Comment below for any other Query or Help related to Chemistry.
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