The S-Block Elements (VSAQs)

Chemistry-1 | 9. The S-Block Elements – VSAQs:
Welcome to VSAQs in Chapter 9: The S-Block Elements. This page includes the important FAQs for Very Short Answer Questions. Answers are provided in simple English and follow the exam format. This approach helps in focusing on essential points and achieving top marks in your final exams.

VSAQ-1 : Describe the important uses of quick lime.

Important Uses of Quicklime:

  1. Manufacture of Cement: Quicklime is a fundamental component in the production of cement. It is heated with silica to form calcium silicate, a key ingredient in cement production.
  2. Dye Industry: Quicklime is used in the dye industry to manufacture certain dyes and dye intermediates.
  3. Production of Sodium Carbonate (Soda Ash): Quicklime plays a role in the production of sodium carbonate (soda ash) from caustic soda (sodium hydroxide).
  4. Purification of Sugar: Quicklime is employed in the purification of sugar. It helps in the removal of impurities from sugar cane juice during the sugar refining process.

VSAQ-2 : Describe the important uses of Caustic Soda (or) Sodium hydroxide.

Important Uses of Caustic Soda (Sodium Hydroxide):

  1. Soap and Paper Industries: Caustic soda is a key ingredient in soap production and is used in the pulp and paper industry for delignification and bleaching processes.
  2. Petroleum Refining: Sodium hydroxide is employed in petroleum refining to remove impurities and neutralize acidic components, facilitating the production of high-quality fuels.
  3. Mercerizing Cotton: It is used in the textile industry for mercerizing cotton, a process that enhances its strength, luster, and dye affinity.
  4. Laboratory Reagent: Sodium hydroxide is widely utilized in laboratory settings as a chemical reagent for various experiments and analytical procedures.

VSAQ-3 : Describe the important uses of sodium carbonate.

Important Uses of Sodium Carbonate (Na2CO3):

  1. Water Softening: Sodium carbonate is employed to remove water hardness caused by calcium and magnesium ions, making it valuable for water treatment.
  2. Glass Production: It is a crucial component in the manufacturing of glass, where it aids in lowering the melting point and improving the clarity of the glass.
  3. Laundry Detergent: Sodium carbonate is used as washing soda in laundry detergents to enhance the cleaning effectiveness by softening water and assisting in stain removal.
  4. Industrial Processes: Sodium carbonate finds applications in various industries, including paper manufacturing, where it regulates pH, and in the production of paints and petroleum products.

VSAQ-4 : Give the biological importance of Na+ and K+ ions.

Biological Importance of Na+ and K+ Ions:

Na+ (sodium) and K+ (potassium) ions are vital for

  1. Cell Membrane Potential: Establishing and maintaining the electrical potential difference (membrane potential) across cell membranes, essential for nerve impulses, muscle contractions, and cellular processes.
  2. Nerve and Muscle Function: Initiating nerve impulses and regulating muscle contractions.

VSAQ-5 : Mention the important uses of Mg metal.

Important Uses of Mg Metal:

  1. Alloys: Magnesium is used in the creation of strong and lightweight alloys when combined with metals like Aluminum (Al), Zinc (Zn), Manganese (Mn), and Tin (Sn).
  2. Flares and Signals: It plays a crucial role in the production of flash powders and bulbs, making it essential for flares, fireworks, and signal devices.
  3. Dental Care: Magnesium carbonate (MgCO3) is a vital component found in toothpaste, contributing to dental hygiene.

VSAQ-6 : What is the importance of Ca2+ in the functioning of cell?

Importance of Ca2+ in Cell Function:

  1. Bone and Teeth Support: Ca2+ is essential for the strength and structure of bones and teeth, providing a sturdy framework for the body.
  2. Heart Function: These ions play a crucial role in regulating the rhythm of the heartbeat, contributing to proper cardiovascular function.
  3. Blood Clotting: Ca2+ ions are necessary for the blood clotting process, preventing excessive bleeding when injuries occur.
  4. Muscle Contraction: They are essential for muscle contraction, enabling various physical movements and activities.

VSAQ-7 : What is Baking soda? Give its uses.

Baking Soda (Sodium Bicarbonate):

Baking soda, or Sodium bicarbonate (NaHCO3), is a white crystalline powder.

Uses of Baking Soda:

  1. Medicine: It serves as an antacid, helping to relieve indigestion and heartburn.
  2. Effervescent Drinks: Baking soda is used in effervescent drinks, creating a fizzy sensation when dissolved in water.
  3. Fire Extinguishers: It’s employed in fire extinguishers to release carbon dioxide (CO2), smothering fires by cutting off oxygen.
  4. Cooking: Baking soda acts as a leavening agent in cooking, making dough and batter rise, commonly used as baking powder.

VSAQ-8 : What is plaster of paris? Mention its uses.

Plaster of Paris

Plaster of Paris is a semi-hydrated form of Calcium sulfate (CaSO4, 1/2 H2O).

Uses of Plaster of Paris:

  1. Surgical Bandages: It’s used in making surgical bandages for immobilizing bone fractures and providing support during healing.
  2. Chalk Production: Plaster of Paris is a key ingredient in making white chalks, widely used in schools and offices.
  3. Casting: It’s utilized for creating casts in various applications, such as statues, architectural features, roofing, and toy production.

VSAQ-9 : Write the average composition of Portland cement.

Average Composition of Portland Cement

  1. CaO (Calcium Oxide): 50 – 60%
  2. SiO2 (Silicon Dioxide): 20 – 25%
  3. Al2O3 (Aluminum Oxide): 5 – 10%
  4. MgO (Magnesium Oxide): 2 – 3%
  5. SO3 (Sulfur Trioxide): 1 – 2%
  6. Fe2O3 (Iron Oxide): 1 – 2%

VSAQ-10 : Why are IA group elements called as “alkali metals”?

IA group elements, including Li (Lithium), Na (Sodium), K (Potassium), Rb (Rubidium), Cs (Cesium), and Fr (Francium), are referred to as “alkali metals” because of their characteristic reaction with water. When these metals come into contact with water, they undergo a vigorous chemical reaction, resulting in the formation of hydroxides (alkaline substances). These hydroxides are highly alkaline in nature, which means they have a high pH level, making the solution strongly basic or “alkaline.” Hence, these elements are named “alkali metals” due to their tendency to produce alkaline solutions when they react with water.

VSAQ-11 : Why gypsum is added to cement?

Gypsum is added to cement to control and extend the setting time. When gypsum is mixed with cement, it retards the setting process, making it slower. This is beneficial because it allows more time for the concrete or cement mixture to be worked with and placed before it starts to harden. As a result, the construction process becomes more manageable, and the cement can achieve the desired strength and durability as it gradually hardens over time.

VSAQ-12 : Why are alkali metals not found in the free state in nature?

Alkali metals are highly reactive due to their low ionization energy and one valence electron. They readily form compounds by reacting with substances like oxygen and water, which is why they are not found in a free state in nature.

VSAQ-13 : What happens when magnesium metal is burnt in air?

When magnesium metal is burnt in air, it produces a bright, dazzling light and forms magnesium oxide (MgO) due to its reaction with oxygen (O2). Additionally, some magnesium nitride (Mg3N2) can also be produced when magnesium reacts with nitrogen gas (N2).

VSAQ-14 : Lithium reacts with water less vigorously than sodium. Give your reasons.

Lithium reacts with water less vigorously than sodium because of its smaller size and higher hydration energy compared to sodium.

VSAQ-15 : Lithium salts are mostly hydrated. Why?

Lithium salts are predominantly hydrated because lithium, being the smallest among alkali metals, can more effectively polarize water molecules. This results in a higher degree of hydration for Li⁺ ions compared to other alkali metals. For instance, lithium chloride (LiCl) typically forms hydrates, such as LiCl•2H2O, due to this strong interaction with water molecules.

VSAQ-16 : Write completely the electronic configuration of K and Rb.

  1. Electronic Configuration of K (Potassium, Atomic Number 19): 1s2 2s2 2p6 3s2 3p6 4s1
  2. Electronic Configuration of Rb (Rubidium, Atomic Number 37): 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1

VSAQ-17 : Which of the alkali metals shows abnormal density? What is the order of the variation of density among the IA group elements?

The order of variation of density among the IA group (alkali metals) elements is as follows, starting from the lowest density to the highest:

  1. Lithium (Li): Abnormal density compared to the trend.
  2. Sodium (Na): Relatively higher density than lithium.
  3. Potassium (K): Higher density than sodium.
  4. Rubidium (Rb): Higher density than potassium.
  5. Cesium (Cs): Higher density than rubidium.
  6. Francium (Fr): Theoretical element, not commonly found, so its density is not well-established.

VSAQ-18 : Potassium carbonate cannot be prepared by Solvay process. Why?

Potassium carbonate (K2CO3) cannot be produced using the Solvay process because the Solvay process is not suitable for the manufacture of K2CO3. This limitation arises because potassium bicarbonate (KHCO3), which would be an intermediate compound, is more soluble in water compared to sodium bicarbonate (NaHCO3). As a result, KHCO3 cannot be easily isolated from the solution, making the Solvay process impractical for potassium carbonate production.

VSAQ-19 : Why does the solubility of alkaline earth metal hydroxides in water increases down the group?

The solubility of alkaline earth metal hydroxides increases down the group because, as you move down the group, the decrease in lattice enthalpy (energy required to break the ionic lattice) is more significant than the decrease in hydration enthalpy (energy released when ions are surrounded by water molecules). This means that as you go down the group, the ionic size increases, weakening the attraction between the metal cation and hydroxide ion in the solid lattice. As a result, the compounds become more soluble in water.