IX Practical Chemistry KBSE Experiment No. 7

To Prepare Carbon Dioxide and study its properties.

Viva Voce
Q.1. Who discovered Carbon Dioxide?

Ans. Von Hemont in 17th Century and Joseph Black in 1728 discovered Carbon Dioxide.


Q.2. What happens when wood or any other substance containing Carbon is heated in a free

supply of air?

Ans. Carbon Dioxide is formed.


Q.3. What happens when carbon is burnt in insufficient supply of air?

Ans. Cabon Monoxide is obtained.


Q.4. What happens when Carbonates are heated?

Ans. All carbonates except Na2Co3 and K2Co3 give out Carbon Dioxide on heating.

CaCO3 -------> CaO + CO2


Q.5. What happen if Bicarbonates are heated?

Ans. Bicarbonates also on heating give pure Carbon Dioxide.

2KHCO3 ------> K2CO3 + H2) + CO2


Q.6. How will you prepare Carbon Dioxide in the laboratory?

Ans. Carbon Dioxide is prepared in the laboratory by the action of dil HCl on marble chips

or limestone CaCO3

CaCO3 + 2HCl ------> CaCl2 + H2O + CO2


Q.7. What is the molecular weight of CO2?

Ans. 44.


Q.8. Write down the name of the apparatus which are used in the experiment?

Ans. Woulffe's Bottle, Delivery Tube, Gas Jars.


Q.9. Which size of the trough is used in this experiment?

Ans. No trough is required because CO2 is highly soluble in water.


Q.10. At what angle should the delivery tube be bent?

Ans. Delivery tube should be bent twice at Right angle.


Q.11. Whether the gas is heavier or lighter than air?

Ans. Gas is heavier than air.


Q.12. How many times Carbon Dioxide is heavier than air?

Ans. It is 1.5 times heavier than air.


Q.13. By which method should the gas be collected?

Ans. It should be collected by downward displacement of gas.


Q.14. In what position should the thistle funnel be kept?

Ans. It should be kept dipped in acid so that the gas may not escape.


Q.15. If you a given a choice of acid, which acid will you prefer from sulphuric acid and

Hydrochloric acid?

Ans. We will prefer Hydrochloric acid (HCl) because of the reason that H2SO4 produce Calcium

Sulphate (CaSO4) which forms a coating over marble and further reaction is prevented.

Moreover CaSO4 forms a hard mass on the vessel and it becomes difficult to clean it. In case

of HCl Soluble CaCl2 (Calcium Chloride) is formed and so no such difficulty arises.


Q.16. How will you know that the Jar is full with gas?

Ans. A burning match stick is brought near the mouth of the Jar it gets extinguished.

OR

A moist blue litmus paper brought near the mouth of the Jar becomes red.


Q.17. What is the colour of the Gas?

Ans. It is Colourless.


Q.18. Why is it so that smoke containing CO2 is coloured?

Ans. It contains unburnt Carbon particles which remain in colloidal state in Carbon Dioxide.


Q.19. What is the smell of the Gas?

Ans. It is odourless.


Q.20. What is the taste of the Gas?

Ans. It is acidic taste.


Q.21. Is it poisonous?

Ans. NO, it is not poisonous.


Q.22. Is Carbon Monoxide poisonous?

Ans. Yes it is poisonous.


Q.23. Can you pour Carbon Dioxide like water from one Jar to another Jar?

Ans. Yes it can be poured like water from one Jar to another Jar because it is 1 1/2 times

heavier than water.


Q.24. What is the effect of pressure on the solubility of CO2?

Ans. Its solubility increases with increase of pressure.


Q.25. What are necassary precautions in this experiment?

Ans.

1. The apparatus should be air tight.

2. Dry gas jars should be used to collect Carbon Dioxide as it is soluble in water.

3. The lower end of thistle funnel should be immersed in the liquid.


Q.26. What is the Chemical name and formula of Marble?

Ans. Marble is Calcium Carbonate and its Chemical formula is CaCO3.


Q.27. Why does lime water become milky when CO3 is passed through it.

Ans. Lime water becomes milky due to formation of insoluble Calcium Carbonate.

CO2 + Ca(OH)2 --------> CaCO3 + H2O.


Q.28. What happens when Carbon Dioxide is passed in excess through lime water?

Ans. When Carbon Dioxide is passed through lime water then Calcium Carbonate is formed which

is insoluble. Later on insoluble calcium Carbonate becomes soluble due to formation of

Calcium Bicarbonate.

CO2 + Ca(OH)2 -------> CaCO3 + H2O

CO2 + CaCO3 + H2O ---> Ca(HCO3)2.


Q.29. Why is it so that a burning match stick gets extinguished when introduced in a jar

of Carbon Dioxide?

Ans. Burning Match stick gets extinguished when introduced into Carbon Dioxide jar because

this gas's non-supporter of combustion.


Q.30. What is the effect of aqueous solution of Carbon Dioxide on blue litmus paper?

Ans. Blue litmus paper becomes red because aqueous solution of CO2 is acidic.


Q.31. What are some uses of Carbon Dioxide?

Ans.

1. It is used as Fire Extinguisher.

2. It is used in the manufacturer of aerated water.

3. It is used in the preparation of Sodium Carbonate.

4. Dry Ice (Solid form of CO2) is used in medicine.


Q.32. Does Carbon Dioxide support the combustion of burning magnesium wire?

Ans. Yes, it suppurts the combustion of burning magnesium wire

Mg + CO2 ---------> MgO + C


Q.33. What is the name of the compound which is formed after the ignition of Magnesium

Wire?

Ans. White powder of Magnesium Oxide is formed.


Q.34. Why do you collect Carbon Dioxide by downward displacement of Gas?

Ans. It is due to the reason that Carbon Dioxide is heavier than air.


Q.35. Why should the apparatus be air tight?

Ans. Carbon Dioxide will escape into atmosphere, if the apparatus is not air tight.


Q.36. What are tess for Carbon Dioxide?

Ans. It extinguishes the burning match stick at once.


Q.37. What are the other methods of preparation of Carbon Dioxide ?

Ans. It may also be prepared by the following methods.

1. By the action of acids of Bicarbonate.

NaHCO3 + HCl ---------> NaCl + H2O + CO2

2. By heating Bicarbonates or Carbonates of heavy metals.

2NaHCO3 ----------> Na2CO3 + CO2 + H2O

ZnCO3 ------------> ZnO + CO2.

3. By burning carbon in air.

C + O2 -----------> CO2


Q.38. Why do you call Carbon Dioxide as "Carbonic Acid Gas"?

Ans. Carbon Dioxide is soluble in water forming Carbonic Acid which turns blue litmus red. A

Carbon Dioxide produces this acid by combining with water it is called Carbonic Acid Gas.


Q.39. Why burning Magnesium wire continues to burn in the jar of Carbon Dioxide?

Ans. Due to excessive heat of burning Magnesium Wire the Carbon Dioxide is decomposed into

Carbon and Oxygen. The oxygen combines with the magnesium forming white powder of Magnesium

Oxide and a black deposit of Carbon.

2Mg + CO2 ---------> 2MgO + C.


Q.40 What are the chemicals required in the preparation of Carbon Dioxide?

Ans. Calcium Carbonate (CaCO3) and Hydrochloric Acid (HCl) are required for the preparation

of Carbon Dioxide.


Q.41. What is Dry Ice?

Ans. Solid Carbon Dioxide is called "Dry Ice".


Q.42. Why should the lower end of the thistle funnel be immersed in the liquid?

Ans. If the lower end of the thistle funnel is not immersed in the liquid the gas will

escape through the thistle funnel and will not be collected in the gas jar.


Q.43. Which substance is obtained if Carbon Dioxide is dissolved in water?

Ans. Carbonic Acid (H2CO3) is obtained when Carbon Dioxide is dissolved in water.


Q.44. Why does the milkiness disappear when Carbon Dioxide is passed through lime water

is excess?

Ans. The milkiness disappears due to formation of soluble Calcium Bicarbonate.


Q.45. Is Carbon Dioxide an element or a Compound?

Ans. Carbon Dioxide is a Compound of Carbon and Oxygen and its formula is CO2.


Q.46. Can any other compound be used instead of CaCO2?

Ans. Yes we can use any other metallic carbonate e.g. Na2CO3. It is due to the fact that HCl

reacts with metallic carbonates and decomposes them into respective chlorides and Carbon

Dioxide.


Q.47. Show the reaction of HCl on Marble Chips?

Ans. CaCO3 + 2HCl --------> CaCl2 + H2O + CO2.


Q.48. If we bring a burning match stick near the mouth of the gas jar then it gets

extinguished. Which property of Carbon Dioxide is displayed by this fact.

Ans. Carbon Dioxide is not a supporter of Combustion.


Q.49. Generally Carbon Dioxide is non supporter of combustion but burning magnesium wire

continues to burn. Why is it so?

Ans. It is due to the reason that heat produced by burning magnesium wire decomposes CO2

into Carbon and Oxygen and the Oxygen obtained helps it in burning brilliantly.


Q.50. Which are other metals which continue burning in it?

Ans. Highly reactive metals like Sodium, Potassium continue to burning in it.


Q.51. Write down the formulae of the following. Slaked LIme, Milk of Lime, Lime water.

Ans. All these substances have got the same formula Ca(OH)2.


Q.52. What is the nature of the gas?

Ans. It is acidic in nature and turns moist blue litmus red.


Q.53. What is the action of quick lime on Carbon Dioxide?

Ans. Quick Lime is converted to CaCO3.


Q.54. Why is it not collected by downward displacement of water?

Ans. It is soluble in water.


Q.55. What is the formula of Slaked Lime?

Ans. Ca(OH)2.


Q.56. What happens if quick lime is exposed to air?

Ans. It absorbs CO2 from air and changes into CaCO3.


Q.57. What is the formula of Carbonic Acid?

Ans. H2CO3.


Q.58. What is the formula of Lime Water?

Ans. Ca(OH)2.


Q.59. What is the difference between Slaked Lime and Lime Water?

Ans. Slaked Lime is in powdered state and when if slightly dissolves in water forms lime

water.


Q.60. What is left behind in Woulffe's Bottle after preparing this gas?

Ans. Calcium Chloride and Water.


Q.61. Why is it called Acid Gas?

Ans. It is called Acid Gas because it turns blue litmus red and it is sour in taste.


Q.62. Why Co2 is used in aerated Water?

Ans. It is used in aerated water because it helps in digestion and provides taste.


Q.63. Why do we keep the thistle funnel dipped in the liquid?

Ans. The thistle funnel is kept dipped in liquid so that the gas may not escape.


Q.64. What happens when a small animal is placed in Carbon Dioxide Jar?

Ans. It dies due to suffocation but it is not poisonous.


Q.65. How can you prove that the apparatus is air tight?

Ans. We can prove it by blowing air from the outer end of the delivery tube. If water rises

in the thistle funnel then it is air tight.