Olympiad Science - Combustion and Pressure
Exam Duration: 45 Mins Total Questions : 30
What are the two main hydrocarbons present in L.P.G.?
- (a)
Butane + propane
- (b)
Butane + isobutane
- (c)
Propane + ethane
- (d)
Methane + ethane
L.P.G.is a mixture of hydrocarbons. It consists of butane, propane and ethane but butane and propane are the two major constituents of L.P.G.
Which of the following has the highest calorific value?
- (a)
Petrol
- (b)
Coke
- (c)
Natural gas
- (d)
Kerosene
Natural gas has the highest calorific
value of 50000 kJ/kg
Petrol has 45000 kJ/kg
Kerosene has 45000 kJ/kg and
Coke has 28000 kJ/kg
Which of the following has the characteristics of a good fuel?
- (a)
Coke
- (b)
Butane
- (c)
Coal
- (d)
Kerosene
All the given substances can act as fuels but butane is considered as a good fuel because of the following characteristics:
(i) Exists in gaseous state
(ii) Has high calorific value
(iii) Does not form poisonous products during combustion
What is burning of a substance in the presence of air with the evolution of heat called
- (a)
Distillation
- (b)
Carbonisation
- (c)
Combustion
- (d)
Refining
The process of a substance burning in the presence of air with evolution of heat is called combustion.
When methane burns in air, what are the products formed?
- (a)
CO2 + 2H2O + heat
- (b)
CO2 + H2
- (c)
CO + 02
- (d)
CO2+ 02 + heat
Fuels and hydrocarbons burn in oxygen and form CO2 , H2O and give out heat.
CH4 + 202 \(\longrightarrow \) CO2 + 2H2O + heat
What kind of reaction is combustion?
- (a)
Reduction
- (b)
Redox
- (c)
Substitution
- (d)
Oxidation
Combustion is an oxidation reaction accompanied by heat and light.
Which of the following is a combustible substance?
- (a)
Coke
- (b)
Coal
- (c)
Diamond
- (d)
Wood
Diamond is a non-combustible substance.
What is the lowest temperature at which a substance starts burning called?
- (a)
Minimum temperature
- (b)
Maximum temperature
- (c)
Boiling temperature
- (d)
Ignition temperature
The temperature at which a substance starts burning on heating is called ignition temperature. Highly inflammable substances have a low ignition temperature. Hence, they catch fire easily.
If the temperature falls below its ignition temperature, then what happens to the burning substance
- (a)
It gets extinguished.
- (b)
It burns brightly.
- (c)
It burns dimly.
- (d)
It burns with smoke
A burning substance will be extinguished-if the temperature falls below its ignition temperature
Which of the following is an example of rapid combustion
- (a)
Candle
- (b)
Cracker
- (c)
White phosphorus
- (d)
Sulphur
Rapid combustion is a form of combustion in which large amounts of heat and light energy are released. Candle shows rapid combustion, whereas cracker and white phosphorous come under explosion and spontaneous combustion respectively.
In which of the following types of combustion are heat, light and sound produced?
- (a)
Rapid
- (b)
Explosive
- (c)
Spontaneous
- (d)
All of the above
The combustion in which heat, light and sound are produced is known as explosive combustion.
Match the entries in Column-I with those in Column-II correctly
- (a)
a-l, b-2, c-3, d-4
- (b)
a-2,b-3,c-4,d-l
- (c)
a-3,b-4,c-2,d-l
- (d)
a-4,b-l,c-2,d-3
The correct combination is a - 3, b - 4, c - 2, d - 1
(i) Dark inner zone - Unburnt vapours of wax
(ii) Blue zone - Complete combustion
(iii) Luminous zone - Partial combustion
(iv) Non-luminous zone - Hottest part (no carbon)
What does the blue zone in an L.P.G. flame indicate?
- (a)
Unburnt vapours
- (b)
Partial decomposition
- (c)
Moderately hot
- (d)
Hottest zone of complete combustion
The blue zone in L.P.G.flame indicates the hottest zone where complete combustion takes place
What does natural gas contain?
- (a)
Methane, ethane, propane.
- (b)
Butane, propane and ethane.
- (c)
Pentene, methane and ethylene.
- (d)
Hexane, butane and ethane.
Natural gas consists of methane, ethane, propane etc., of which methane forms major composition of about 95%
How is synthetic petrol produced?
- (a)
From petroleum
- (b)
From wood
- (c)
From coal
- (d)
From L.P.G
The Bergius Process is a very simple process for converting brown coal completely into crude oil. It was invented by Dr. Friedrich Bergius. In this process, brown coal, also known as lignite is powdered and mixed with heavy oil and heated with hydrogen under high pressure of about 200-250 atm. and a temperature of about 748 K in the presence of iron oxide as catalyst The vapours on condensation give a liquid resembling crude oil. This is called synthetic petrol, which on fractional distillation gives petrol (gasoline).
Arrange the following fuels in the increasing order of their calorific value
- (a)
(i),(ii), (iii), (iv)
- (b)
(ii), (iii), (iv) and (i)
- (c)
(ii), (i), (iii) and (iv)
- (d)
(ii), (iii), (i) and (iv)
(i) Wood - 17000 to 22000 kJ/kg
(ii) Coal - 25000 to 33000 kJ/kg
(iii) Petrol - 45000 kJ/kg
(iv) Natural gas - 50000 kl/kq
The correct order of the increasing order of calorific values is : (ii),(iii),(i),(iv).
What does the incomplete combustion of a fuel give?
- (a)
CO
- (b)
CO2
- (c)
S02
- (d)
Oxidesofnitrogen
When a fuel (carbon) undergoes incomplete combustion, carbon monoxide is formed. It is a poisonous gas and fatal, if inhaled.
What is combustion?
- (a)
An exothermic reaction
- (b)
An endothermic reaction
- (c)
A displacement reaction
- (d)
A reduction reaction
Combustion is burning of a substance in the presence of oxygen.During this process heat energy is released, it is therefore an oxidation and exothermic reaction.
Inspite of the danger involved with hydrogen, it is used for some applications. Where is it used?
- (a)
Rocket fuel
- (b)
Oxyhydrogen flame
- (c)
Car fuel
- (d)
All of the above
Though hydrogen is a highly combustible gas, because of its high calorific value, it is used as rocket fuel,for cutting and welding metals in the form of oxyhydrogen flame and as a car fuel under stringent safety conditions.
A family consumes 12 kg of L.P.G. in 30 days. Calculate the average energy consumed per day, if the calorific value of L.P.G.is 50 kJ kq-1.
- (a)
10,000 J per day
- (b)
15,000 J per day
- (c)
20,000 J per day
- (d)
25,000 J per day
Energy released by 12 kg of L.P.G.in 30 days
= No. of kg of gas utilised by a family in
30 daysx calorific value of gas.
\(\frac { 12 }{ 30 } \)\(\times \)50=20KJ/day
Therefore, energy consumed per day:
= 20,000 joules/day.
What ignition temperature does an inflammable substance have
- (a)
More than 100 °C
- (b)
Less than 100 °C
- (c)
More than 200 °C
- (d)
Between 200 °C to 350 °C
Inflammable substances have very low ignition temperatures, so they catch fire easily.
e.q. alcohol, ether, carbon disulphide, benzene, synthetic fibres etc.
What is the disadvantage of incomplete combustion of a fuel?
- (a)
Unburnt carbon gets released.
- (b)
Air gets polluted.
- (c)
Respiratory problems arise.
- (d)
All of the above
Incomplete combustion of a fuel results in the formation of unburnt carbon and some poisonous gaseslike'CO'and oxides of nitrogen which cause air pollution leading to many respiratory problems
Which of the following is the best extinguisher for inflammable materials?
- (a)
Water
- (b)
Sulphur dioxide
- (c)
Carbon dioxide
- (d)
Carbon monoxide
Carbon dioxide is the best extinguisher for inflammable materials like petrol, because it is heavier than oxygen, it covers fire like a blanket. Since, the contact between the fuel and oxygen is cut off, the fire is controlled, Secondly,it does not harm the electrical equipment It can also be used to put out fires involving electrical equipment.
On which of these factors does the flame produced by a fuel depend upon?
- (a)
Calorific value
- (b)
Amount of oxygen
- (c)
The chemical composition of a fuel
- (d)
All of the above
The type of fuel involved in the combustion determines the type of flame (colour and temperature of a flame varies with the chemical composition of the fuel).
Which of the following statements is NOT true?
- (a)
CO2 is the best fire extinguisher.
- (b)
Global warming can cause acid rain
- (c)
Burning of coal and diesel releases sulphur dioxide gas.
- (d)
L.P.G.has higher calorific value than biogas.
Global warming may cause glaciers to melt, which may lead to a rise in the sea level and thus submerge low lying areas
Hydrogen gas has the highest calorific value i.e., 150 kJ kg-1, yet it is not used as a fuel. Why?
- (a)
It is explosive in nature.
- (b)
It causes storage problem.
- (c)
It causes transportation problem.
- (d)
All of the above
The availability of hydrogen is less and also forms an explosive mixture with air or oxygen and causesexplosion if it leaks out Its storage and transport are difficult
For a spontaneous combustion to take place, which condition given below is necessary?
- (a)
Flame
- (b)
Low ignition temperature
- (c)
Rise in temperature
- (d)
Temperature below 30°C
For spontaneous combustion to take place, a substance should have low ignition temperature:
e.g., The ignition temperature of phosphorus is 35° C
An electric spark is struck between two electrodes placed near each other, inside a closed tank full of petrol. What will happen?
- (a)
Spontaneous combustion of petrol
- (b)
Explosion
- (c)
Slow combustion of petrol
- (d)
Nothing will happen
A tank filled with petrol implies there is no air/oxygen inside the tank. As there is no supporter of combustion, burning of petrol does not takes place though spark is brought nearer to it .
One gram of which of these will give out the maximum amount of heat by complete combustion?
- (a)
Wood
- (b)
Coal
- (c)
Diesel
- (d)
Biogas
Diesel will give out maximum amount of heat by complete combustion when compared with wood, coal and biogas.
Which of the following statements is NOT true?
- (a)
Spontaneous combustion takes place without any apparent cause.
- (b)
The luminous zone of a flame has high temperature.
- (c)
Carbon dioxide gas causes global warming.
- (d)
The calorific value of a fuel is expressed in kJ / kg -1
It is not the luminous zone but the nonluminous zone of the flame that has a very high temperature,