s-block elements Test - 1

• Castner Kellner cell is also called a mercury cathode cell.
• In this cell, Hg flows along the bottom of the cell and acts as a cathode in the left-hand compartment fitted with graphite anodes in brine (NaCl) solution, whereas the right-hand compartment is fitted with Fe cathodes dipped in very dilute NaOH solution and Hg acts as the anode in this compartment.
• Thus, Hg acts as an intermediate electrode by induction, cathode on LHS and anode in RHS.

Heating limestone at a temperature of 1070K we get quick lime i.e CaO.

CaCO₃ ⇌ CaO (s) + CO₂ (s)

Additional Information: Calcium oxide can be produced by the thermal decomposition of materials like limestone or seashells that contain calcium carbonate in a lime kiln.

On passing CO₂ gas, Ca(OH)₂ becomes CaCO₃ (milky white ppt.) which proves the presence of CO₂.

If CO₂ is passed through slaked lime(calcium hydroxide Ca(OH)₂), it gives out calcium carbonate (CaCO₃) also called marble/limestone.

CO₂ + Ca(OH)₂→ CaCO₃+ H₂O

• Teeth are composed of calcium, phosphorus, and other minerals. 
• Bones contain calcium, phosphorus, sodium and other minerals, but mostly consist of the protein collagen.

Additional Information: The hardest part of the human body, teeth mostly consist of a calcified tissue called dentin. The tooth's dentine tissue is covered in enamel, that hard, shiny layer that you brush.

In the Castner-Kellner method NaOH is prepared by the electrolysis of an aqueous solution of NaCl(Brine).

Additional Information: The Castner Kellner process is a method of electrolysis of sodium chloride solution to produce alkali hydroxide. It uses electrolytes of NaCl solution graphite anode and mercury cathode.

Slaked lime (milk of lime) reacts with chlorine gas to produce the bleaching agent calcium hypochlorite – a common form of 'swimming pool' chlorine.

• Sodium carbonate, Na₂CO₃, (washing soda) is the water-soluble sodium salt of carbonic acid, well-known domestically for its everyday use as a water softener.
• Pure sodium carbonate is a white, odorless powder that is hygroscopic (absorbs moisture from the air).
• It has a strongly alkaline taste and forms a moderately basic solution in water.

Crystallization: A chemical solid-liquid separation technique in which mass transfer of a solute from the liquid solution to a pure solid crystalline phase occurs.

Additional Information:

• Crude sodium chloride, generally obtained by the crystallization of brine solution, contains sodium sulphate, calcium sulphate, calcium chloride and magnesium chloride as impurities.
• To get pure sodium chloride first the crude sodium chloride is dissolved in a minimum amount of water and filtered to remove insoluble impurities.
• Now into the saturated solution of sodium chloride hydrogen chloride gas is passed.
• Then pure sodium chloride crystallizes.
• The other compounds which are present in small amounts such as MgCl2MgCl2 and CaCl2CaCl2 remain in solution.

Calcium hypochlorite is an inorganic compound with the formula Ca(OCl)₂. It is the main active ingredient of commercial products called bleaching powder.