Combustion and flame Worksheet-5

Combustion and flame Worksheet-5

Multiple Choice Questions:

31. The products obtained on complete combustion are _____.

A. Carbon                                       B. CO

C. CO₂                                             D. None of these

32. Goldsmith uses ____ part of the flame for melting gold

A. Outermost                                B. Middle

C. Innermost                                 D. Middle & Innermost

33. Amount of heat energy produced on _____combustion of 1kg of fuel is Calorific value.

A. Incomplete                               B. Complete

C. Half                                            D. None of these

34. Element showing spontaneous combustion is _____.

A. Calcium                                     B. White Phosphorous

C. Lithium                                     D. Copper

35. Which of the following is/are carbon fuel

A. Wood                                          B. Coal

C. Petroleum                                 D. All of these

36. Combustion of most fuels releases _____.

A. CO₂                B. SO₂                 C. NO₂                D. Oxygen

37. Burning of coal and diesel releases ______.

A. NO₂                B. CO₂                C. SO₂                 D. CO

38. Petrol engine gives off gaseous oxides of _____.

A. Sulphur                                      B. Nitrogen

C. Phosphorous                            D. Carbon

39. Acid rain is caused by oxides of _____.

A. Sulphur, Nitrogen                   B. Sulphur, Carbon

C. Carbon, Nitrogen                    D. Phosphorous, Carbon

40. In the sun, heat and light are produced by_______.

A. Chemical reactions                 B. Nuclear reactions

C. Ionic reactions                         D. None of these

41. Coal and charcoal do not produce flame because:

A. They undergo complete combustion producing carbon dioxide and water

B. They do not vapourise during burning so do not produce flames.

C. They undergo incomplete combustion hence do not produce flame

D. None of these

42. When the match struck against rubbing surface, red phosphorous

A. Converts into white phosphorous

B. Reacts with potassium chlorate

C. Ignite antimony trisulphide

D. None of these

43. Best extinguisher for inflammable Materials is ______.

A. Water            B. SO₂                 C. CO₂                D. CO

44. CO₂ is stored as a liquid in cylinder at ______.

A. High pressure                          B. Low pressure

C. High temperature                   D. Low temperature

45. CO₂ is given off by chemicals like_______.

A. Sodium bicarbonate               B. Calcium sulphate

C. Sodium sulphate                     D. Sulphuric acid

46. Water is not suitable for fire involving

A. Oil                                               B. Petrol

C. Oil & Petrol                               D. None of these

Answer:

31. C

32. A

Explanation: Outermost part of the flame is hottest due to complete combustion of fuel.

33. B

34. C

35. D

36. A

37. C

38. B

39. A

40. B

41. B

42. A

43. C

Explanation: Carbon dioxide extinguishes fire by forming a blanket over fire thus cutting off the supply of oxygen. Carbon dioxide sprayed from the extinguisher is very cold hence it reduces the temperature of fuel also.

44. A

45. A

46. C