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ChemistryClass 10ICSE

• (a) What is the common name of the compound CaOCl2? (b) Name the raw material used for the preparation of plaster of Paris. (c) Which property of plaster of Paris is utilised in making casts for broken limbs in hospitals? Explain why chlorine is used for sterilising drinking water supply.

Solution: Bleaching powder Gypsum Plaster of Paris has the property of setting into hard mass after Chlorine is the best for sterilising drinking water supply because it kills all the bacteria and germs present in the water. It acts as a disinfectant

ChemistryClass 10ICSE

State two uses each of the following compounds: (a) Sodium hydroxide (b) Chlorine (c) Hydrogen (d) Hydrochloric acid.

Sodium hydroxide: Used for making soaps Manufacturing of paper Chlorine Used in the production of bleaching powder Used for sterilising drinking water Hydrogen Used as fuels in rockets Used in hydrogenation of oils Hydrochloric acid Used in medicines and cosmetics Textile dyeing and tanning industries

ChemistryClass 10ICSE

What is "baking powder"? How does it make the cake soft and spongy? (b) In addition to sodium hydrogencarbonate, baking powder contain a substance X. Name the substance. What is the role of substance X in the baking powder?

(a) Baking powder is a mixture of baking soda and tartaric acid when mixed with water the sodium hydrogen carbonate reacts with tartaric acid carbon dioxide gas is liberates and trapped in wet dough and bubbles out slowly making the cake soft and spongy. (b) Substance X is tartaric acid and it reacts with sodium carbonate formed and neutralise it otherwise cakes and breads will taste bitter.

ChemistryClass 10ICSE

What is gypsum ? What happens when gypsum is heated to 100℃ (373K)? (b) Name a sodium compound which is used for making borax and glass. (c) Name the compound which is used in hospitals for setting fractured bones. Which is the real bleaching powder agent in the bleaching powder?

Gypsum is calcium sulphate dehydrate (CaSO4.2H2O) and when heated to a temperature of 373K it loses three-fourth of its water of crystallization and forms plaster of Paris (CaSO4.1/2H2O) Sodium carbonate or washing soda is used to make borax and glass Plaster of Paris is used for setting fractured bones because on addition of water to this turns hard mass and if we mould a layer around the fractured part it solidifies and supports the damaged bone hence heal the fracture. Bleaching powder is also called calcium chlorohypochlorite because a little of mixture of hydrochloric acid and hypochlorous acid

ChemistryClass 10ICSE

Name a sodium compound used for softening hard water. (b) Which compound of calcium is used for disinfecting drinking water supply? (c) Name a metal compound which has detergent properties (cleansing properties). (d) Name one compound of calcium which is used for removing colour of a coloured cloth.State a peculiar (or remarkable) property of plaster of Paris. Name the substance obtained by the action of chlorine on solid (dry) slaked lime.

Sodium carbonate is used for softening hard Commonly called washing soda Bleaching powder is a calcium compound which is used for disinfecting drinking water Sodium carbonate is the metal compound which has detergent and cleansing property Bleaching powder or calcium oxychloride ( CaOCl2) is used for removing the colour Plaster of Paris has a property of setting into hard mass on addition of Bleaching powder or calcium oxychloride ( CaOCl2) is obtained by the action of chlorine on solid slaked lime

ChemistryClass 10ICSE

What is the chemical name of bleaching powder? (b) What is the chemical formula of bleaching powder? (c) What are the materials used for the preparation of bleaching powder? State one use of bleaching powder (other than bleaching).

Chemical name of bleaching powder is calcium oxychloride CaOCl2 Calcium hydroxide and Bleaching powder is used as a disinfectant in the drinking water which kills germs and

ChemistryClass 10ICSE

Name two constituents of baking powder. (b) How does baking powder differ from baking soda? (c) Explain the action of baking powder in the making of cake (or bread). Write equation of the reaction involved.

Sodium hydrogencarbonate and tartaric acid are the constituents of baking Baking powder is a mixture of baking soda and tartaric acid and baking soda is only sodium bicarbonate. They looks similar in appearance On mixing baking powder with water in the making of cake the sodium bicarbonate reacts with tartaric acid to evolve carbon dioxide gas and it gets into the wet dough and bubbles Thus the cake become soft and spongy NaHCO3(aq) + H+ → Na+(aq) + CO2(g) + H2O(l)

ChemistryClass 10ICSE

What happens when copper sulphate crystals are heated strongly? Explain with the help of an example. (b) What happens when a few drops of water are added to anhydrous copper sulphate? Explain with the help of an equation.

(a) Copper sulphate crystals when heated strong it loses the water and the blue colour will turn to white CuSO4.5H2O → CuSO4 + 5H2O (b) When water is added to anhydrous copper sulphate, it gets hydrated and turns blue. CuSO4 + 5H2O → CuSO4.5H2O

ChemistryClass 10ICSE

What will happen if heating is not controlled while preparing Plaster of Paris? (b) Write an equation to show the reaction between plaster of Paris and water.

(a) If heating is not controlled while preparing Plaster of Paris, then all the water of crystallisation of gypsum is eliminated and it turns into a dead burnt plaster. (b) CaSO4.1/2H2O + 1 1/2H2O → CaSO4.2H2O

ChemistryClass 10ICSE

What is the common name of sodium hydrogencarbonate?(b) What happens when a solution of sodium hydrogencarbonate is heated? Write the equation of the reaction involved. Explain why, sodium hydrogencarbonate is used as an antacid.

Baking soda is the common name of sodium hydrogencarbonate When a solution of sodium hydrogencarbonate is heated, then it decomposes to give sodium carbonate with an evolution of carbon dioxide gas 2NaHCO3 → Na2CO3 + CO2 + H2O Sodium hydrogencarbonate is used as an antacid because the function of antacid is neutralizing the excess acid present in the stomach and helps to get relief from indigestion

ChemistryClass 10ICSE

What is meant by "water of crystallisation" in a substance? Explain with an example. (b) How would you show that blue copper sulphate crystals contain water of crystallisation? (c) Explain how anhydrous copper sulphate can be used to detect the presence of moisture (water) in a liquid.

Water of crystallisation is that the water molecules that form part of the structure of a crystal of a For example the washing soda crystals contains 10 molecules of water of crystallisation and represented as Na2CO3.10H2O Copper sulphate crystals are blue in colour CuSO4.5H2O and when is heated it loses water and will become white in colour. Thus we can conclude that the blue colour is due to water of crystallization Take a drop of the liquid which to be tested and add to white anhydrous copper sulphate The blue colour indicates the presence of moisture or water

ChemistryClass 10ICSE

What happens when a cold and concentrated solution of sodium chloride reacts with ammonia and carbon dioxide? Write the chemical equation of the reaction which takes place.

When a cold and concentrated solution of sodium chloride reacts with ammonia and carbon dioxide 2 products are formed sodium hydrogen carbonate and ammonium chloride → NaHCO3 + NH4Cl NaCl + NH3 + H2O + CO2

ChemistryClass 10ICSE

Describe how sodium hydrogen carbonate (baking soda) is produced on a large scale. Write equation of the reactions involved.

Baking soda is produced in large scale by reacting a cold and concentrated solution of sodium chloride called brine with ammonia and carbon dioxide → NaHCO3 + NH4Cl NaCl + NH3 + H2O + CO2

ChemistryClass 10ICSE

What is baking soda? Write the chemical name of baking soda. Give the important uses of baking soda. How does baking soda differ chemically from washing soda?

Baking soda is a substance which is added to the food stuff to cook fast. It is a sodium salt. The chemical name of baking soda is sodium hydrogencarbonate which is also called sodium bicarbonate. Baking soda is used in fire extinguishers and also used in preparing baking powder and also in baking cakes etc. Washing soda and baking soda is different. Washing soda consist of two sodium atoms attached to carbonate group and baking soda have one atom of sodium and one hydrogen. Both differs in one hydrogen atom

ChemistryClass 10ICSE

Write the chemical formula of ammonium chloride. Explain why an aqueous solution of ammonium chloride is acidic in nature? Illustrate your answer with the help of a chemical equation.

The chemical formula of ammonium chloride is NH4Cl. It is formed from a weak base, ammonium hydroxide and a strong acid. Ammonium chloride when dissolved in water it hydrolyses to form ammonium hydroxide and hydrochloric acid NH4Cl + H2O → NH4OH + HCl The formed hydrochloric acid is strong acid and it ionizes to give H+ ions whereas ammonium hydroxide is weak base and give small amount of OH- ions on dissociation.

ChemistryClass 10ICSE

Write the formulae of sodium chloride and sodium carbonate. Explain why an aqueous solution of sodium chloride is neutral but an aqueous solution of sodium carbonate is basic (or alkaline). Write chemical equations of the reactions involved.

Sodium chloride - NaCl. Sodium carbonate - Na2CO3. Aqueous solution of sodium chloride is neutral because it is formed from strong acid and strong base. The aqueous solution of sodium carbonate is alkaline because it is prepared fromm the reaction of weak acid and a strong base. Na2CO3(s) + 2H2O(l) → 2NaOH(aq) + H2CO3(aq)

ChemistryClass 10ICSE

What is washing soda? State two properties and two uses of washing soda.

Washing soda is sodium carbonate decahydrate It is a white crystalline solid and soluble in water It is highly alkaline substance having property of removing dirt Washing soda is used in soap, glass, and paper industries It is used in the manufacture of sodium compounds such as borax.

ChemistryClass 10ICSE

Complete and balance the following equations: (a) NaCl(aq) + H2O(l) → (b) 2NaHCO3 → (c) NaCl + NH3 + H2O + CO2 → (d) Ca(OH)2 + Cl2 →

NaCl(aq) + H2O(l) → 2NaOH(aq) + Cl2(g) + H2(g) 2NaHCO3 → Na2CO3 + CO2 + H2O NaCl + NH3 + H2O + CO2 → NaHCO3 + NH4Cl Ca(OH)2 + Cl2 → CaOCl2 + H2O

ChemistryClass 10ICSE

Fill in the following blanks: (a) Common salt is obtained from sear water by the process of ……. (b) Rock salt is mined just like ……. (c) Chemical formula of washing soda is …… (d) Sodium hydrogencarbonate is ………… soda whereas sodium carbonate is …. Soda The chemical formula of plaster of Paris is ……

Evaporation Coal Na2CO10H2O Baking soda; washing soda CaSO1/2H2O

ChemistryClass 10ICSE

During electrolysis of a saturated solution of sodium chloride, where is : (a) Chlorine formed? (b) Hydrogen formed? Sodium hydroxide formed?

During the electrolysis of a saturated solution of sodium chloride, chlorine gas is produced at the anode which is positive chloride Hydrogen gas is produced at the cathode that is negative Sodium hydroxide is formed near the

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