Description : Why is yellow flame is an example of combustion?
Last Answer : fvfvfvffvf
Description : During combustion of unsaturated compounds a ______ is seen. (1) clean flame (2) blue flame (3) red flame (4) yellow flame
Last Answer : (4) yellow flame Explanation: When saturated compounds are burnt in air,they give a clear(blue) flame due to complete combustion. However the burning of unsaturated compounds (alkenes and alkynes) gives a sooty (yellowish) flame due to incomplete combustion.
Description : Bunsen burner is an example of a/an __________ burner. (A) Inside mixing/premix type (B) Outside mixing/diffusion flame/nozzle mix type (C) Rotary cup (D) Submerged combustion
Last Answer : (A) Inside mixing/premix type
Description : What kind of combustion is observed in alkanes? Why do air holes of a gas burner have to be adjusted when vessel being heated gets blackened by the flame? -Science
Last Answer : Alkanes are saturated hydrocarbons and generally burn in air with a blue, non-sooty flame. If the bottoms of the cooking vessels in our homes are getting blackened, it shows that the air holes of the gas stove are getting blocked and the fuel is not burning completely.
Description : In case of liquid petrofuels, momentary combustion is observed at its (A) Flash point (B) Preheating temperature corresponding to viscosity of 25 centistokes (C) Flame temperature (D) Fire point
Last Answer : (A) Flash point
Description : Oxygen enrichment of combustion air does not result in increase of the (A) Flame temperature (B) Oxygen in the flue gas (C) Stack loss (D) Heat transfer rate in the furnace
Last Answer : (B) Oxygen in the flue gas
Description : Advantages of use of preheated combustion air are (A) Saving in fuel consumption (B) Reduction in scale losses (C) Increase in flame temperature (D) All (A), (B) and (C)
Last Answer : (D) All (A), (B) and (C)
Description : Combustion of fuel in a furnace with oxygen enriched air results in higher (A) Flue gas volume (B) Flame temperature (C) Fuel consumption (D) Stack loss
Last Answer : (B) Flame temperature
Description : Which of the following advantages is not associated with the use of preheated air for combustion of a fuel in the furnace? (A) Increase in calorific value of the fuel (B) Increase in flame temperature (C) Reduction in scale losses (D) Saving in fuel consumption
Last Answer : (A) Increase in calorific value of the fuel
Description : Pick out the wrong statement. (A) Theoretical flame temperature is the temperature attained by the products of combustion, when the fuel is burned without loss or gain of heat (B) ... flame temperature (D) Adiabatic flame temperatures of actual combustions are always less than the maximum values
Last Answer : (C) Burning the fuel with excess pure oxygen results in maximum theoretical flame temperature
Description : A coal having high amount of volatile matter (A) Would require smaller combustion chamber (B) Produces very little of tar and gas on carbonisation (C) Ignites easily and burns with long smoky flame (D) All (A), (B) and (C)
Description : During combustion of gaseous fuels, deficiency of air (A) Lengthens the flame (B) Tends to shorten the flame (C) Does not affect the flame length (D) Increases the flame temperature
Last Answer : (A) Lengthens the flame
Description : Deficiency of combustion air during combustion of a gaseous fuel (A) Lengthens the flame (B) Causes heat loss of fuel by its partial combustion (C) Both (A) & (B) (D) Shortens the flame
Last Answer : (C) Both (A) & (B)
Description : Preheating of combustion air is done to (A) Increase the adiabatic flame temperature (B) Increase the calorific value of the fuel (C) Complete the combustion of fuel (D) Reduce its requirement for effecting the complete combustion
Last Answer : (A) Increase the adiabatic flame temperature
Description : Actual flame temperature is always lower than the adiabatic flame temperature, because there is (A) No possibility of obtaining complete combustion at high temperature (B) Always loss of heat from the flame (C) Both (A) and (B) (D) Neither (A) nor (B)
Last Answer : (C) Both (A) and (B)
Description : Combustion of pulverised coal as compared to that of lump coal (A) Develops a non-luminous flame (B) Develops a low temperature flame (C) Can be done with less excess air (D) Provides a lower rate of heat release
Last Answer : (C) Can be done with less excess ai
Description : Use of excess of combustion air in the combustion of fuels results in (A) Heat losses (B) Long flame (C) Condensation of water vapour from the fuel gas (D) None of these
Last Answer : (A) Heat losses
Description : During combustion of a gaseous fuel, the presence of a non-luminous flame is an indication of the (A) Incomplete combustion (B) Complete combustion (C) High oxygen in flue gas (D) None of these
Last Answer : (B) Complete combustion
Description : With increase in calorific value of fuels, their adiabatic flame temperatures (A) Increase (B) Decrease (C) Remain unchanged (D) May increase or decrease; depends on the quantity of products of combustion
Last Answer : (D) May increase or decrease; depends on the quantity of products of combustion
Description : Coke oven gas is a better fuel than blast furnace gas, because of its higher (A) Calorific value, cleanliness and relatively low distribution cost (due to its low specific gravity) (B) Adiabatic flame temperature ... release rate (thus requiring smaller combustion chamber) (D) All (A), (B) and (C)
Description : Presence of nitrogen in combustion air does not reduce the (A) Amount of heat liberated (B) Flame temperature (C) Flue gas temperature (D) Any of the above
Last Answer : (A) Amount of heat liberated
Description : Preheating of __________ the flame temperature. (A) The gaseous fuel before combustion decreases (B) Combustion air decreases (C) Either the fuel or the air or both, increases (D) Either the fuel or the air does not affect
Last Answer : (C) Either the fuel or the air or both, increases
Description : For the case of a fuel gas undergoing combustion with air, if the air/fuel ratio is increased, the adiabatic flame temperature will (A) Increase (B) Decrease (C) Increase or decrease depending on the fuel type (D) Not change
Last Answer : (B) Decrease
Description : Short/intense flame is produced during combustion of gaseous fuel by using (A) High amount/current of combustion air (B) Low amount/current of combustion air (C) Preheated secondary air (D) Very little excess air
Last Answer : (A) High amount/current of combustion air
Description : A fuel with high heat release rate will (A) Require smaller combustion chamber (B) Have high calorific value (C) Have high adiabatic flame temperature (D) None of these
Last Answer : (A) Require smaller combustion chamber
Description : A coal having high ratio of volatile matter to fixed carbon as compared to a coal having low ratio of volatile matter to fixed carbon (A) Is less liable to spontaneous combustion on storage (B) ... a shorter flame (C) Requires smaller combustion space and less secondary air (D) None of these
Last Answer : (D) None of these
Description : Use of preheated air for combustion of fuel in the furnace, increases the (A) Scale losses of the furnace stock (B) Calorific value of the fuel (C) Flame temperature (D) None of these
Last Answer : (C) Flame temperature
Description : Combustion of pulverised coal compared to the lumpy coal (A) Provides better control of furnace temperature (B) Facilitates combustion with lower excess air (C) Provides higher thermal efficiency & flame temperature (D) All (A), (B) & (C)
Last Answer : (D) All (A), (B) & (C)
Description : High excess air in combustion of fuels results in (A) Increased fuel consumption (B) Incomplete combustion (C) Smoky flame (D) None of these
Last Answer : (A) Increased fuel consumption
Description : If the specific heat of gaseous products of combustion of a fuel is high, the abiabatic flame temperature will be (A) Low (B) High (C) Very high, if the fuel is of low calorific value (D) None of these
Last Answer : (A) Low(A) Low
Description : Which of the following is not increased by using preheated combustion air in place of ordinary air at room temperature? (A) Calorific value of the fuel (B) Flame temperature achieved (C) Speed of combustion of fuel (D) Heat transfer rate to the stock in the furnace
Last Answer : (A) Calorific value of the fuel
Description : Pick out the wrong statement. (A) Strongly caking coal should not be used in the Lurgi gasifier (B) Acetylene gas cannot be used for illumination purpose (C) Water gas is called blue gas ... is burnt (D) Gaseous fuels require less percentage of excess air for combustion as compared to liquid fuels
Last Answer : (B) Acetylene gas cannot be used for illumination purpose
Description : Presence of moisture in fuel oil would (A) Keep the burner tips cool (B) Aid in proper combustion (C) Because sputtering, possibly extinguishing flame (D) Clean the nozzles
Last Answer : (D) Clean the nozzles
Description : Which metal burns to produce bright yellow flame ?
Last Answer : Burning sodium produces a bright yellow flame.
Description : Why should you turn a Bunsen burner to a yellow flame if you need to leave it?
Last Answer : The yellow flame is more visible - making it easier for othersto see. It's also a colder flame than the blue conical one.
Description : Give reason: Glass objects when held to flame acquires golden yellow colour.
Last Answer : The sodium content of sodium silicate present in glass makes the flame to acquire golden yellow colour to the flame.
Description : Anthracite coal (A) Contains more volatile matter than bituminous coal (B) Ignites more easily than bituminous coal (C) Is essentially a coking coal (D) Burns with short, bluish, yellow-tipped flame producing very little smoke
Last Answer : (D) Burns with short, bluish, yellow-tipped flame producing very little smoke
Description : The hottest part of the flame lies in its _________zone. (A) Non-luminous (B) Luminous (C) Yellow (D) Unburnt gases
Last Answer : (A) Non-luminous
Description : Bituminous coal (A) Ignites less easily than anthracite (B) Is generally coking (C) Burns with smoky yellow flame (D) Both (B) and (C)
Last Answer : (D) Both (B) and (C)
Description : What is an external combustion engine? Give example.
Last Answer : A heat engine in which combustion of fuel takes place outside the cylinder of the engine is called external combustion engine. Ex: Steam engine.
Description : The Classical example of redox reaction is Combustion of fossil fuel. During combustion of fossil fuels, the carbon compound in the fossil fuel reacts with oxygen in the presence of a heat source to ... to react with oxygen, so the energy used in portion of combustion is an endothermic reaction.
Last Answer : Combustion of fossil fuel