Acids, Bases and Salts _ Part 5

Acids, Bases and Salts _ Part 5

by utkersh bora

​What is common salt and How is it obtained?

​Sodium chloride (NaCl) is also known as Common or Table Salt. It is formed after the reaction between sodium hydroxide and hydrochloric acid.

NaOH + HCl—–> NaCl + water​

​On a large scale sodium chloride can be obtained as:

a. Common salt from sea water.

b. Common salt from underground deposits.

Multiple Choice

Why is the colour of Rock Salt Brown?

• Due to all the impurities present in the salt along with sodium chloride.

• Due to the charred NaCl molecules.

• Due to weathering conditions.

• None of the above

Multiple Choice

Which of the following is not a use of Common Salt (NaCl):

• It is used as a raw material for making sodium hydroxide, sodium carbonate, baking soda etc.

• It is used as a preservative in pickles.

• It is used in the manufacture of soaps as a raw material.

• It is used in the preparation of Plaster of Paris.

​What is Caustic Soda?

​Sodium Hydroxide is commonly known as Caustic Soda. The formula of sodium hydroxide is NaOH.

​​It is produced by electrolysis of a concentrated aqueous solution of sodium chloride (which is called brine solution). When electricity is passed through an aqueous solution of sodium chloride (called brine), it decomposes to form sodium hydroxide.

The process is called the chlor-alkali process because of the products formed– chlor for chlorine and alkali for sodium hydroxide.

2NaCl(aq) + 2H₂O(l) → 2NaOH(aq) + Cl₂ (g) + H₂ (g)

Multiple Choice

Identify the correct representation of reaction occurring during the chlor-alkali process.

• 2NaCl(l)+2H₂O(l)→2NaOH(l)+Cl₂(g)+H₂(g)

• 2NaCl(s)+2H₂O(aq)→2NaOH(aq)+Cl₂(g)+H₂(g)

• 2NaCl(aq)+2H₂O(l)→2NaOH(aq)+Cl₂(aq)+H₂(aq)

• 2NaCl(aq)+2H₂O(l)→2NaOH(aq)+Cl₂(g) + H₂(g)

Multiple Choice

Name the gases obtained at the Anode and Cathode respectively during the Chlor-Alkali Process.

• Cl₂, H₂

• H₂, Cl₂

• Cl₂, O₂

• H₂, O₂

​What is bleaching powder?

​Bleaching Powder is calcium oxychloride. It is also called as the chloride of lime. The chemical formula of bleaching powder is CaOCl₂.

Bleaching powder is produced by the action of chlorine on dry slaked lime [Ca(OH)_2].

​

Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O

Multiple Choice

What is the chemical formula for Bleaching Powder/ chloride of lime?

• Ca (OH)₂

• CaOCl₂

• CaCl₂

• None of the above

Multiple Choice

Which of the following are the uses of Bleaching Powder?

• For bleaching cotton and linen in the textile industry, for bleaching wood pulp in paper factories and for bleaching washed clothes in laundry

• As an oxidising agent in many chemical industries;

• To make drinking water free from germs.

• All of the above.

Multiple Choice

Bleaching powder (also known as calcium oxychloride ) is commercially produced by the action of chlorine on ____________________?

• Slaked lime

• Soda lime

• Calcium perchlorate

• None of these

​What is Baking Soda?

​The baking soda is commonly used in the kitchen for making tasty crispy pakoras, etc. Sometimes it is added for faster cooking. The chemical name of the compound is sodium hydrogencarbonate (NaHCO₃).

It is produced using sodium chloride as one of the raw materials.

NaCl + H₂O + CO₂ + NH₃ → NH₄Cl + NaHCO₃

Multiple Choice

Which of the following are the uses of Baking Soda?

• For making baking powder, which is a mixture of baking soda and a mild edible acid such as tartaric acid.

• Sodium hydrogencarbonate is also an ingredient in antacids. Being alkaline, it neutralises excess acid in the stomach and provides relief.

• It is used in soda-acid fire extinguishers

• All of the Above

Multiple Choice

The Chemical Formula for Baking Soda is:

• NH₄Cl

• NaHCO₃

• Na₂CO₃

• NaCl

​What is Washing Soda?

​Washing soda is sodium carbonate containing 10 molecules of water of crystallisation. It is called as sodium carbonate decahydrate. The formula of washing soda is Na₂CO₃ . 10H₂O.

​

Sodium carbonate which does not contain any water of crystallisation is called anhydrous sodium carbonate or soda ash. The formula is Na₂CO₃.

​Preparation of Washing Soda

It is prepared by Solvay’s process.

(1) Sodium hydrogen carbonate (baking Soda) is heated to form sodium carbonate (Soda ash).

​2NaHCO₃ → Na₂CO₃ + H₂O + CO₂

​(2) Anhydrous sodium carbonate is dissolved in water and recrystallised to get washing soda crystals containing 10 molecules of water of crystallisation.

​Na₂CO₃ + 10H₂O → Na₂CO₃. 10H₂O

​Properties of Washing Soda

(1) It is a white transparent crystalline solid.

(2) It is soluble in water.

(3) The solution of washing soda in water is alkaline which turns red litmus to blue.

(4) It has cleansing properties.

​

Uses of Washing Soda

(1) It is used to remove permanent hardness of water.

(2) It is used in the manufacture of glass,soap,paper.

(3) It is used for washing clothes.

(4) It is used in the manufacture of borax.

Multiple Choice

What is the Chemical Formula for Soda Ash?

• Na₂CO₃

• NaHCO₃

• Na₂CO₃.10H₂O

• None of the above

Multiple Choice

What is the Chemical Formula for Washing Soda?

• Na₂CO₃

• NaHCO₃

• Na₂CO₃.10H₂O

• None of the above

Multiple Choice

Solvay's Process is used in the preparation of:

• Common Salt

• Slaked Lime

• Washing Soda

• Bleaching Powder

Multiple Choice

Which Chemical Compound is added to remove the permanent hardness of water?

• Baking Powder

• Common Salt

• Caustic Soda

• Washing Soda

​What is Plaster of Paris?

​Plaster of paris (P.O.P.) has the chemical name calcium sulphate hemihydrate. The chemical formula of Plaster of paris is CaSO₄ ·½H₂O.

Here, half a water molecule is shown to be attached as water of crystallisation. It is written in this form because two formula units of CaSO₄ share one molecule of water.

​

​Preparation:

On heating Gypsum (CaSO₄ .2H₂O) at 373 K, it loses water molecules and becomes plaster of paris (CaSO₄ ·½H2O)

​CaSO₄ .2H₂O→ CaSO₄ ·½H₂O + 1½ H₂O

​Properties of Plaster of Paris

(1) It is a white powder.

(2) It has a very remarkable property of setting into a hard mass on wetting with water, and so P.O.P. should be stored in a moisture proof container.

​

Uses of Plaster of Paris

(1) It is used in hospitals for setting fractured bones in the right position to ensure correct healing.

(2) It is used in making toys, decorative materials, cheap ornaments, cosmetics, blackboard and casts for statues.

(3) It is used in chemistry laboratories for sealing air gaps in apparatus where air-tight arrangement is required.

(4) It is used for making surfaces smooth before painting.

Multiple Choice

Plaster of Paris is:

• CaSO₄.½H₂O

• Used for setting of broken bones

• Both A and B

• Same as Gypsum

Multiple Choice

Plaster of Paris is obtained by heating:

• Gypsum

• Limestone

• Sodium Carbonate

• Calcium Sulphate

​What is the water of Crystallization?

​Water of crystallisation is a fixed number of water molecules present in one formula unit of a salt. One formula unit of copper sulphate contains five water molecules (5H₂O). The water molecules which form part of the structure of a crystal are called water of crystallisation. When hydrated salts are heated strongly, they lose their water of crystallisation.

​

On strong heating, blue copper sulphate crystals turn white grey (due to the loss of water of crystallisation).

​

​CuSO₄.5H₂O → CuSO₄ + 5H₂O

Multiple Choice

What is the color of anhydrous copper sulphate?

• Blue

• White grey

• Blue grey

• Greenish

Multiple Choice

What is the color of hydrated copper sulphate?

• Blue

• White grey

• Red grey

• Greenish

Multiple Choice

What is called water of crystallization?

• Salt water

• Water consumed while crystallization of salts

• Water molecules present in salt crystals

• Minimum amount of water which is required for crystallization of salts