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The s-block Elements — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistryThe s-block Elements5 Marks
Question
  1. When alkali metals are heated in excess of air, what is the nature of oxides formed?
  2. How can you prepare baking soda?
  3. Which is having more reducing characteristics out of alkali metals and alkaline earth metals?
  4. Alkaline earth metals impart a characteristic colour to the flame but Be and Mg do not give. Why?
  5. Write balanced equations for the reactions between $Na_2O$ and $CO_2$.
✓

Answer

  1. The oxides formed are basic in nature. Lithium The oxid forms monoxide, sodium forms peroxide whereas K, Rb and Cs form superoxides.
  2. $\text{NH}_3+\text{CO}_2+\text{H}_2\text{O}\xrightarrow{\ \ \\ \ \ \ \ \ \ \ }(\text{NH}_4)\text{HCO}_3$
$\text{NH}_4\text{HCO}_3+\text{NaCl}\xrightarrow{\ \ \\ \ \ \ \ \ \ \ }\text{Na}\text{HCO}_3+\text{NH}_4\text{Cl}\\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{Baking soda}$
  1. Alkali metals are stronger reducing agents than alkaline earth metals due to lower ionization energy and low reduction potential.
  2. Be and Mg have high I.E., therefore, do not absorb light from visible region and do not radiate colour. Others have low I.E., they absorb light from visible region and radiate complementary colour.
  3. $\text{Na}_2\text{O}+\text{CO}_2\xrightarrow{ \ \ \ \ \ \ \ }\text{Na}_2\text{CO}_3$

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