MCQ 511 Mark
What does natural gas contain?
- ✓
Methane, ethane, propane.
- B
Butane, propane and ethane.
- C
Pentene, methane and ethylene.
- D
Hexane, butane and ethane.
AnswerCorrect option: A. Methane, ethane, propane.
Natural gas consists of methane, ethane, propane etc, of which methane forms major composition of about $95\%$.
View full question & answer→MCQ 521 Mark
The suspended particles released by combustion of coal in air may lead to a health disease. Select the correct option.
AnswerSuspended particulate matter $(SPM)$ refers to microscopic solid or liquid matter suspended in the Earth's atmosphere. Air pollutants consist of gaseous pollutants, odours, and $SPM$, (suspended particulate matter) such as dust, fumes, mist, and smoke. The high concentration of these in and near urban areas causes severe pollution to the surroundings. High amount of $SPM$ in air leads to respiratory problems and lung related diseases like asthma.
View full question & answer→MCQ 531 Mark
The amount of heat energy produced on complete combustion of _______ fuel is called its calorific value.
- A
$1$ litre
- ✓
$1$Kg
- C
$1$ milli litre
- D
$1$ gram
View full question & answer→MCQ 541 Mark
‘Firework’ is an example of:
MCQ 551 Mark
Which gas is used in fire extinguishers?
AnswerCorrect option: C. $CO_2$
$CO_2$is used in fire extinguishers for dousing fire as it cuts the oxygen supply to the fire.
View full question & answer→MCQ 561 Mark
If the temperature falls below its ignition temperature, then what happens to the burning substance?
AnswerA burning substance will be extinguished if the temperature falls below its ignition temperature.
View full question & answer→MCQ 571 Mark
Which of the following is an example of rapid combustion?
AnswerRapid 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.
View full question & answer→MCQ 581 Mark
Which among the following is considered as the cleanest fuel?
AnswerHydrogen gas is considered as cleanest fuel. Unlike carbon based fuels, hydrogen produces no harmful by-products on combustion. Only energy and clean water are produced.
View full question & answer→MCQ 591 Mark
Harish performed two different experiments $I$ and $II$. In experiment $I$, he provides a substance $'X$? with some heat. He found out that a sudden reaction takes place to form heat, light, and sound. In experiment $II$, he provides heat to a substance $'Y$?. He found out that when $Y$ bums, only heat and light are produced. Experiment $I$ represents an example of __$i$__, and experiment II represents an example of __$ii$___. The information in which alternative completes the given statement?
- ✓
$i$-Explosion, $ii$-Rapid combustion.
- B
$i$-Explosion, $ii$-Sportaneous combustion.
- C
$i$-Spontaneous combustion,$ii$-Explosion.
- D
$i$-Rapid combustion, $ii$-Spontaneous combustion.
AnswerCorrect option: A. $i$-Explosion, $ii$-Rapid combustion.
A substance when burns to produce huge amount of heat, light, and sound represents an example of explosion. On the other hand, when a substance burns rapidly to produce huge amount of heat and light represents an example of rapid combustion. Hence, experiment I represents an explosion, whereas experiment II represents a rapid combustion.
View full question & answer→MCQ 601 Mark
In the sun, light and heat are produced by:
MCQ 611 Mark
Rajiv took three substances $P, Q,$ and $R$ and burnt them one by one. He noted down his observations given below.
$I.$ Substance $P$ bums quickly producing heat and light.
$II.$ Substance $Q$ bums in room temperature on its own.
$III.$ Substance $R$ bums with the evolution of heat, light, and sound. Which of the following statements regarding the given information is correct?
- A
Substances $P$ and $Q$ are undergoing rapid combustion whereas $R$ is undergoing explosion.
- B
Substances $P$ and $R$ are undergoing spontaneous combustion whereas $Q$ is undergoing rapid combustion.
- ✓
Substance $P$ is undergoing rapid combustion, $Q$ is undergoing spontaneous combustion while $R$ is undergoing explosion.
- D
Substance $P$ is undergoing spontaneous combustion, $Q$ is undergoing rapid combustion while $R$ is undergoing explosion.
AnswerCorrect option: C. Substance $P$ is undergoing rapid combustion, $Q$ is undergoing spontaneous combustion while $R$ is undergoing explosion.
Substances which burn rapidly and produce heat and light are said to undergo rapid combustion. The substances that burn on their own at room temperature are said to undergo spontaneous combustion. The substances which burn with the evolution of heat, light, and sound are said to undergo explosion.
View full question & answer→MCQ 621 Mark
What is the principle of soda fire extinguisher?
- ✓
Carbon dioxide produced cuts off the supply of oxygen by covering the fire like a blanket.
- B
Water produced cuts off the supply of oxygen by covering the fire.
- C
Acid present in the container reacts with fire.
- D
Nitrogen gas produced cuts off the supply of oxygen by covering the fire.
AnswerCorrect option: A. Carbon dioxide produced cuts off the supply of oxygen by covering the fire like a blanket.
Carbon dioxide being heavier than oxygen, covers the fire like a blanket. Since the contact between the fuel and oxygen is cut off, the fire is controlled.
View full question & answer→MCQ 631 Mark
The calorific value of a fuel is $40000kJ/ kg$. This fuel is most likely to be:
AnswerBiogas has calorific value of $40000Kj/Kg$.
View full question & answer→MCQ 641 Mark
The given table lists the ignition temperatures of four fuels $W, X, Y,$ and $Z$ respectively.
|
Fuel Ignition
|
Temperature
|
|
$W$
|
$38^\circ C$
|
|
$X$
|
$42^\circ C$ |
|
$Y$
|
$53^\circ C$ |
At $50^\circ C$, which of the given fuels is likely to undergo combustion? - ✓
$Y$ and $Z$
- B
$X$ and $Y$
- C
$W$ and $X$
- D
$Z$ and $W$
AnswerCorrect option: A. $Y$ and $Z$
The ignition temperature of a substance is the lowest temperature at which that substance starts burning. Both fuels, $W$ and $X$,have their ignition temperatures below $50^\circ C$. Hence, they will attain their ignition temperatures and undergo combustion.
View full question & answer→MCQ 651 Mark
On placing an inverted tumbler over a burning candle, the flame extinguishes after some time. This is because of nonavailability of
AnswerThe flame extinguishes because of non-availability of oxygen. Air or oxygen is necessary for combustion.
View full question & answer→MCQ 661 Mark
In which of the following types of combustion are heat, light and sound produced?
AnswerThe combustion in which heat, light and sound are produced is known as explosive combustion.
View full question & answer→MCQ 671 Mark
When wood is used as a fuel in chullahs, gaps are left in between logs of wood. Why is it done so?
- ✓
To facilitate movement of air.
- B
To prevent more consumption of wood.
- C
- D
AnswerCorrect option: A. To facilitate movement of air.
Gaps are left in between logs of wood placed in chullahs to allow free movement of air, which helps in combustion.
View full question & answer→MCQ 681 Mark
Colours of flame produced by kerosene lamp, candle and Bunsen burner are respectively?
- A
- ✓
- C
- D
Yellow, orange and yellow.
AnswerKerosene lamp - yellow flame Candle - yellow flame Bunsen burner - Blue flame.
View full question & answer→MCQ 691 Mark
View full question & answer→MCQ 701 Mark
A lot of dry powder of one of the following chemicals can be released over a fire to extinguish it. This chemical is:
AnswerTo obtain carbon dioxide for extinguishing a fire is to release a lot of dry powder of chemicals like sodium bicarbonate (baking soda) or potassium bicarbonate over the fire.
View full question & answer→MCQ 711 Mark
Substances which have very low ignition temperature and can catch fire easily are called:
MCQ 721 Mark
The substance that catches fire spontaneously in presence of air, at room temperature, is:
AnswerHere, the student is required to identify the chemical which glows in presence of oxygen at room temperature. White phosphorous burns in the presence of air and gives bright light and smoke.
View full question & answer→MCQ 731 Mark
Mark the correct statements among the following.
$i.$ Water is a very good fire extinguisher as it cools down the fuels such as wood below its ignition temperature.
$ii.$ Water is a very good fire extinguisher for burning oils and electrical equipment.
$iii.$ Sand and soil may act as a good fire extinguisher for burning oils.
- A
$I$ only
- B
$II$ only
- ✓
$III$ only
- D
$I$ and $III$ only
AnswerCorrect option: C. $III$ only
Water works as a fire extinguisher by taking out the heat from the fire. It is never used in laboratories and electrical stores and in case of burning of oils because it will worsen the fire. Only the fire of paper, wood, or other ordinary materials can be extinguished by water. Sand can be used in laboratories fire, electrical fire and in burning of oils as it cuts off the oxygen supply.
View full question & answer→MCQ 741 Mark
Burning of charcoal in a closed room will produce.
MCQ 751 Mark
- A
The maximum temperature at which a substance catches fire.
- B
The minimum temperature at which a substance catches fire.
- C
The temperature of burning substance.
- ✓
The temperature in the substance when fire if put off.
AnswerCorrect option: D. The temperature in the substance when fire if put off.
The minimum temperature at which a substance catches fire.
View full question & answer→MCQ 761 Mark
Combustion of a substance releases heat and ______.
AnswerCombustion or burning is an exothermic chemical reaction (in the presence of oxygen) that releases a significant amount of heat and light. Light is either in the form of a glow or a flame. Not all substances have a flame when burned. Flame depends on whether or not combustible vapours are released by the fuel. An example of combustion without a flame is the burning of coal. An example of combustion with a flame is a burning candle.
View full question & answer→MCQ 771 Mark
One gram of which of these will give out the maximum amount of heat by complete combustion?
AnswerDiesel will give out maximum amount of heat by complete combustion when compared with wood, coal and biogas.
View full question & answer→MCQ 781 Mark
Consider the following statements and choose the correct one:
- A
The substance which have very low ignition temperature and can easily catch fire with a flame are called inflammable substance.
- B
The amount of heat energy produced on complete combustion of 1kg of a fuel is called its calorific value.
- C
Inflammable substance have very low ignition temperature.
- ✓
AnswerHere, all the statements are correct. Hence, your answer will be option $[d]$.
View full question & answer→MCQ 791 Mark
The substance expected to have the highest ignition temperature out of the following is:
AnswerCoal has the highest ignition temperature.
Note: The lowest temperature at which a substance catches fire and starts burning, is called its ignition temperature. Kerosene, petrol and alcohol have low ignition temperature.
View full question & answer→MCQ 801 Mark
A substance which reacts with oxygen giving heat is called a combustible substance. Which, one of the following is a combustible substance?
AnswerWood is a combustible substance. It is a solid fuel and produces smoke during combustion.
View full question & answer→MCQ 811 Mark
Four substances $P, Q, R,$ and $S$ were brought one by one near a lighted candle. It was observed that only substance $Q$ bums readily. Substances $P$ and $R$ burn after sustained heating and substance $S$ does not bum at all. Among all the substances given, which substance has the lowest ignition temperature?
AnswerIgnition temperature is the minimum temperature at which a substance starts burning. Substance $Q$ burns readily. Hence, it has the minimum ignition temperature. $P$ and $R$ burn, but only after sustained heating. Therefore, their ignition temperature is higher than that of $Q$. $S$ does not burn at all. Therefore, it has the maximum ignition temperature.
View full question & answer→MCQ 821 Mark
Magnesium ribbon on burning in air produces:
- A
Magnesium oxide, water and light.
- B
Magnesium oxide and heat.
- ✓
Magnesium oxide, heat and light.
- D
Magnesium oxide, water and heat.
AnswerCorrect option: C. Magnesium oxide, heat and light.
Magnesium ribbon on burning in air produces magnesium oxide, heat and light, Magnesium ribbon is a very reactive metal.
$\text{magnesium}+\text{Oxygen}\xrightarrow{\text{Combustion}}{\text{Megnesium oxide}}+\text{Heat}+\text{Light}\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ ^{(\text{From air})}$
View full question & answer→MCQ 831 Mark
Geeta took four combustible substances $I, II, II,$ and $IV.$ She found out that the ignition temperatures of $I, II, III,$ and $IV$ is $233^\circ C$, $473^\circ C$, $210^\circ C$, and $170^\circ C$, respectively. She heats all the substances to $190^\circ C$,. Among the given substances, which substance will catch fire when heat is supplied to it?
AnswerDifferent substances catch fire at different temperatures. The ignition temperature of a substance is the lowest temperature at which a substance catches fire or starts burning. A substance cannot catch fire as longs as its temperature is lower than its ignition temperature. When substances $I, II, III,$ and $IV$ are heated to$190^\circ C$by Geeta, only the ignition temperature of substance $IV$ is reached. Thus, only $IV$ will catch fire.
View full question & answer→MCQ 841 Mark
The substances which have very low ignition temperature will
- ✓
- B
- C
Catch fire after some time.
- D
View full question & answer→MCQ 851 Mark
When sufficient oxygen is not available, combustion of methane produces ______ gas and water.
AnswerIncomplete combustion takes place when sufficient amount of oxygen is not present. Incomplete combustion of fuels containing carbon like wood, coal, methane, petroleum, etc releases carbon monoxide $(CO)$ gas which is a very poisonous gas.
View full question & answer→MCQ 861 Mark
Ravi takes three substances $X, Y,$ and $Z$. On heating these substances he observes that they bum at different temperatures. He finds out that $X$ catches fire on little heating, while $Y$ and $Z$ do not catch fire. On further heating of $Y$ and $Z$, he observes that $Y$ catches fire, while $Z$ does not. The correct arrangement of $X, Y,$ and $Z$ in order of their increasing ignition temperatures is:
AnswerThe ignition temperature of a substance is the minimum temperature at which a substance catches fire or starts burning. While $X$ burns on little heating, $Y$ and $Z$ do not burn. This shows that the ignition temperature of $X$ is lower than that of $Y$ and $Z$. On further heating of $Y$ and $Z$, it was found that $Y$ had caught fire at a temperature that was lower than $Z$ (as the latter does not start burning). Thus, it can be concluded that the ignition temperature of $Y$ is lower than that of $Z$. Hence, the correct arrangement of the substances $(X, Y,$ and $Z)$ in order of their increasing ignition temperatures is $X$
View full question & answer→MCQ 871 Mark
Lowest temperature at which a substance catches fire is known as:
MCQ 881 Mark
Different methods of extinguishing a fire involve the following:
$i.$ Removing the combustible substance.
$ii.$ Cooling the substance to a temperature below its ignition temperature.
$iii.$ Cutting off the supply of air.
Which of the following statements is correct?
- A
Method $I$ is suitable in case of a building on fire.
- ✓
Method $II$ involves water which works when wood or paper are on fire.
- C
Method $III$ involves carbon dioxide gas which is lighter than oxygen and forms a blanket around the air.
- D
AnswerCorrect option: B. Method $II$ involves water which works when wood or paper are on fire.
Method $I$ is not possible in case of a building on fire as the entire building is the combustible substance. Method $III$ involves carbon dioxide which is heavier than oxygen and forms a blanket around the fire.
View full question & answer→MCQ 891 Mark
The substance that undergoes combustion is said to be:
MCQ 901 Mark
View full question & answer→MCQ 911 Mark
Sujit took four different beakers $I, II, III,$ and $IV$ each containing $1$ litre water. Also, he took four fuels $W, X, Y,$ and $Z$. Then, he started heating the water in beakers $I, II, III,$ and $IV$ using $1kg$ of each $W, X, Y,$ and $Z$ respectively.He found out that the heat produced by complete combustion of $2kg$ of $W, 4kg$ of $X, 1.2kg$ of $Y,$ and $3.2kg$ of $Z$ is $110000\ kJ, 100000\ kJ, 72000\ kJ,$ and $12800\ kJ$ respectively. Assume that all the heat released by burning the fuel is absorbed by water. In which beaker does the maximum evaporation take place?
AnswerThe higher the calorific value of fuel, the higher is the amount of heat energy released on its combustion. The calorific value of fuel is the amount of heat energy produced by complete combustion of $1kg$ of fuel.
For fuel W: $2kg$ of $W$ produces $110000kJ$ of heat. $1kg$ of $W$ will produce $\frac{110000}{2}\text{kJ}$ of heat.
$= 55000kJ$ of heat
Hence, the calorific value of $W$ is $55000kJ/ kg$.
For fuel X: $4kg$ of $X$ produces $100000kJ$ of heat. $1kg$ of $X$ will produce $\frac{100000}{4}\text{kJ}$ of heat.
$=25000kJ$ of heat
Hence, the calorific value of $X$ is $25000kJ/ kg$.
For fuel Y: $1.2kg$ of $Y$ produces $72000kJ$ of heat. $1kg$ of $Y$ will produce $\frac{72000}{1.2}\text{kJ}$ of heat.
$= 60000kJ$ of heat
Hence, the calorific value of $Y$ is $60000kJ/ kg$.
For fuel Z:$ 3.2kg$ of $Z$ produces $12800kJ$ of heat. $1kg$ of $Z$ will produce $\frac{12800}{3.2}\text{kJ}$ of heat.
$= 4000kJ$ of heat
Hence, the calorific value of $Z$ is $4000kJ/ kg$.
Since the calorific value of $Y$ is the highest $(60000kJ/ kg)$, the water in beaker III will evaporate quickly.
Hence, maximum evaporation takes place in beaker $III$.
View full question & answer→MCQ 921 Mark
Which of the following statement is not correct about carbon dioxide acting as a fire extinguisher for electrical fires?
- A
- ✓
- C
- D
It does not support combustion.
AnswerCarbon dioxide is lighter than air and forms a layer around the burning substance. It covers the fire like a blanket due to which fresh air cannot reach the burning substance.
View full question & answer→MCQ 931 Mark
View full question & answer→MCQ 941 Mark
Consider the following statements, choose the incorrect one:
- A
The forest fires occur during the hottest summer day.
- ✓
It is very difficult to burn a heap of dry leaves.
- C
The head of matchstick contains only antimony tri-sulphide and potassium chlorate.
- D
AnswerCorrect option: B. It is very difficult to burn a heap of dry leaves.
It is very easy to burn a heap of dry leaves. We know that it is difficult to burn a heap of green leaves. The green leaves contain a lot of water. This water does not allow the green leaves to get heated to their ignition temperature easily and makes the burning of green leaves difficult. On the other hand, dry leaves do not contain water, they get heated to their ignition temperature easily and hence can catch fire easily.
View full question & answer→MCQ 951 Mark
Two friends Gaurav and Samik took two glass plates and two lighted candles. Gaurav held the glass plate inside the flame of the candle and Samik held it slightly above the candle flame. Which of the following statements is correct?
- A
Both Gaurav's and Samik's glass plates will get blackish soot deposition.
- B
Neither Samik's nor Gaurav's glass plate will have blackish soot deposition.
- ✓
Gaurav's glass plate will have blackish soot deposition but Samik's glass plate will not.
- D
Samik's glass plate will have blackish soot deposition but Gaurav's glass plate will not.
AnswerCorrect option: C. Gaurav's glass plate will have blackish soot deposition but Samik's glass plate will not.
Gaurav held the glass plate inside the flame. Therefore, he held the plate in the luminous zone. This zone is the zone of incomplete combustion. Therefore, a circular blackish ring will be obtained on his glass plate. Samik held the glass plate slightly above the flame i.e., in the non-luminous zone. As this zone is the zone of complete combustion, no soot deposit will take place in this case.
View full question & answer→MCQ 961 Mark
Why is it never advised to sleep in a room with burning coal fire?
- ✓
Incomplete combustion of coal produces carbon monoxide, which is poisonous.
- B
Incomplete combustion of coal produces carbon dioxide, which is poisonous.
- C
Burning of coal produces oxides of nitrogen, the fumes of which are very toxic.
- D
Burning of coal produces oxides of nitrogen that combine with moisture present in air to form acids.
AnswerCorrect option: A. Incomplete combustion of coal produces carbon monoxide, which is poisonous.
Incomplete combustion of fuels such as coal produces carbon monoxide $(CO)$ gas. Carbon monoxide is a poisonous gas and can even result in death, if inhaled in large quantities. Hence, it is dangerous to burn coal in a closed room while sleeping.
View full question & answer→MCQ 971 Mark
Shyam was cooking potato curry on a chulha. To his surprise he observed that the copper vessel was getting blackened from outside. It may be due to:
- A
Proper combustion of fuel.
- B
Improper cooking of potato curry.
- ✓
Improper combustion of the fuel.
- D
Burning of copper vessel.
AnswerCorrect option: C. Improper combustion of the fuel.
Due to incomplete combustion of fuel, copper vessel was getting blackened from outside.
View full question & answer→MCQ 981 Mark
What is the disadvantage of incomplete combustion of a fuel?
- A
Unburnt carbon gets released.
- B
- C
Respiratory problems arise.
- ✓
AnswerIncomplete combustion of a fuel results in the formation of unburnt carbon and some poisonous gases like $′CO′$ and oxides of nitrogen which cause air pollution leading to many respiratory problems.
View full question & answer→MCQ 991 Mark
The combustion reaction which occurs on its own, without any external supply of heat is called as:
AnswerThe type of combustion in which a material suddenly bursts into flames, without any external heat supply is called spontaneous combustion. For example, substances like phosphorus and sodium burn when kept open at room temperature.
View full question & answer→MCQ 1001 Mark
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