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All questions of Water for Class 9 Exam
What is the effect of pressure on the solubility of gases in liquids?- a)Gas solubility only depends on temperature
- b)Higher pressure increases gas solubility
- c)Higher pressure decreases gas solubility
- d)Pressure has no effect on gas solubility
Correct answer is option 'B'. Can you explain this answer?
What is the effect of pressure on the solubility of gases in liquids?
a)
Gas solubility only depends on temperature
b)
Higher pressure increases gas solubility
c)
Higher pressure decreases gas solubility
d)
Pressure has no effect on gas solubility
 | Mariam Al Saadi answered |
Effect of Pressure on Gas Solubility
The solubility of gases in liquids is significantly influenced by pressure. Here's a detailed explanation of how pressure affects gas solubility:
Henry's Law
- According to Henry's Law, the amount of gas dissolved in a liquid at a given temperature is directly proportional to the partial pressure of that gas above the liquid.
- This means that as you increase the pressure of the gas, more gas molecules are pushed into the liquid, increasing solubility.
Higher Pressure Increases Gas Solubility
- When the pressure above a liquid increases, the gas molecules collide more frequently with the liquid surface.
- This increased interaction leads to more gas molecules entering the liquid, enhancing solubility.
- For example, carbonated beverages are bottled under high pressure. When opened, the pressure decreases, allowing gas to escape, resulting in fizz.
Practical Applications
- This principle is crucial in various industries, including beverage production and scuba diving.
- In scuba diving, as divers descend, the pressure increases, allowing more nitrogen to dissolve in their blood. Upon ascent, if the pressure decreases too quickly, nitrogen can come out of solution, forming bubbles that may cause decompression sickness.
Conclusion
- In summary, option 'B' is correct: higher pressure indeed increases gas solubility. Understanding this principle is essential for both scientific applications and practical scenarios like cooking, beverage production, and diving safety.
The solubility of gases in liquids is significantly influenced by pressure. Here's a detailed explanation of how pressure affects gas solubility:
Henry's Law
- According to Henry's Law, the amount of gas dissolved in a liquid at a given temperature is directly proportional to the partial pressure of that gas above the liquid.
- This means that as you increase the pressure of the gas, more gas molecules are pushed into the liquid, increasing solubility.
Higher Pressure Increases Gas Solubility
- When the pressure above a liquid increases, the gas molecules collide more frequently with the liquid surface.
- This increased interaction leads to more gas molecules entering the liquid, enhancing solubility.
- For example, carbonated beverages are bottled under high pressure. When opened, the pressure decreases, allowing gas to escape, resulting in fizz.
Practical Applications
- This principle is crucial in various industries, including beverage production and scuba diving.
- In scuba diving, as divers descend, the pressure increases, allowing more nitrogen to dissolve in their blood. Upon ascent, if the pressure decreases too quickly, nitrogen can come out of solution, forming bubbles that may cause decompression sickness.
Conclusion
- In summary, option 'B' is correct: higher pressure indeed increases gas solubility. Understanding this principle is essential for both scientific applications and practical scenarios like cooking, beverage production, and diving safety.
What effect does increasing pressure have on the boiling point of water?- a)No effect on the boiling point
- b)Causes water to freeze
- c)Increases the boiling point
- d)Decreases the boiling point
Correct answer is option 'C'. Can you explain this answer?
What effect does increasing pressure have on the boiling point of water?
a)
No effect on the boiling point
b)
Causes water to freeze
c)
Increases the boiling point
d)
Decreases the boiling point
 | Prepworks Coaching answered |
Increasing pressure raises the boiling point of water. This is why pressure cookers can cook food faster; they create a higher-pressure environment that allows water to boil at temperatures above 100°C, leading to quicker cooking times. Conversely, at high altitudes, like on Mount Everest, the lower atmospheric pressure causes water to boil at temperatures below 100°C.
What is an example of a temporary hardness in water?- a)Water with magnesium chloride
- b)Water with sodium carbonate
- c)Water with calcium sulfate
- d)Water with calcium bicarbonate
Correct answer is option 'D'. Can you explain this answer?
What is an example of a temporary hardness in water?
a)
Water with magnesium chloride
b)
Water with sodium carbonate
c)
Water with calcium sulfate
d)
Water with calcium bicarbonate
| | Prepworks Coaching answered |
Temporary hardness is primarily caused by the presence of calcium and magnesium bicarbonates in water. This type of hardness can be removed by boiling, which precipitates the bicarbonates as insoluble carbonates, making the water softer for use.
What happens to water when it undergoes efflorescence?- a)It forms crystals
- b)It absorbs moisture
- c)It loses water and crumbles to powder
- d)It dissolves completely
Correct answer is option 'C'. Can you explain this answer?
What happens to water when it undergoes efflorescence?
a)
It forms crystals
b)
It absorbs moisture
c)
It loses water and crumbles to powder
d)
It dissolves completely
| | Prepworks Coaching answered |
Efflorescence is the phenomenon where hydrated crystals lose their water to the environment, causing them to crumble into a powder. This occurs when the vapor pressure inside the crystals exceeds that of the surrounding air, leading to a dry, powdery residue.
What process involves the conversion of solid water (ice) directly into water vapor without passing through the liquid phase?- a)Freezing
- b)Evaporation
- c)Condensation
- d)Sublimation
Correct answer is option 'D'. Can you explain this answer?
What process involves the conversion of solid water (ice) directly into water vapor without passing through the liquid phase?
a)
Freezing
b)
Evaporation
c)
Condensation
d)
Sublimation
| | Prepworks Coaching answered |
Sublimation is the process where solid water (ice) converts directly into water vapor without first becoming liquid. This phenomenon occurs under specific conditions of pressure and temperature and is commonly observed in nature, such as in snow that seems to disappear on sunny days without melting. Understanding sublimation is important in various fields, including meteorology and physical chemistry.
What is the primary component that contributes to the temporary hardness of water?- a)Calcium bicarbonate
- b)Calcium sulfate
- c)Magnesium chloride
- d)Sodium chloride
Correct answer is option 'A'. Can you explain this answer?
What is the primary component that contributes to the temporary hardness of water?
a)
Calcium bicarbonate
b)
Calcium sulfate
c)
Magnesium chloride
d)
Sodium chloride
| | Prepworks Coaching answered |
The primary component contributing to the temporary hardness of water is calcium bicarbonate. This type of hardness can be removed by boiling, which converts bicarbonates to insoluble carbonates that precipitate out of solution, making the water softer for everyday use.
What is the latent heat of vaporization for water at 100°C?- a)540 cal/g
- b)2268 J/g
- c)1000 J/g
- d)336 J/g
Correct answer is option 'B'. Can you explain this answer?
What is the latent heat of vaporization for water at 100°C?
a)
540 cal/g
b)
2268 J/g
c)
1000 J/g
d)
336 J/g
| | Prepworks Coaching answered |
The latent heat of vaporization for water at 100°C is 2268 J/g (or 540 cal/g). This is the amount of energy required to convert water at its boiling point into steam without changing its temperature. This high energy requirement is why steam burns can be more severe than boiling water burns.
Which of the following statements regarding hard water is true?- a)It is better for washing with soap.
- b)It contains no dissolved minerals.
- c)It can contain bicarbonates, sulfates, or chlorides of calcium and magnesium.
- d)It is the same as distilled water.
Correct answer is option 'C'. Can you explain this answer?
Which of the following statements regarding hard water is true?
a)
It is better for washing with soap.
b)
It contains no dissolved minerals.
c)
It can contain bicarbonates, sulfates, or chlorides of calcium and magnesium.
d)
It is the same as distilled water.
| | Prepworks Coaching answered |
Hard water contains dissolved minerals, specifically bicarbonates, sulfates, or chlorides of calcium and magnesium. These minerals can interfere with the ability of soap to lather, leading to soap curd formation, which is an inconvenience in household cleaning.
Which property of water allows marine life to survive under ice in cold regions?- a)Universal solvent
- b)High specific heat
- c)High boiling point
- d)Densitiy anomaly
Correct answer is option 'D'. Can you explain this answer?
Which property of water allows marine life to survive under ice in cold regions?
a)
Universal solvent
b)
High specific heat
c)
High boiling point
d)
Densitiy anomaly
 | Aurora Institute answered |
The density anomaly of water allows it to be less dense when frozen, causing ice to float. This characteristic means that ice forms a layer on the surface of water bodies, insulating the liquid water beneath, which remains at a temperature that can support marine life even in cold conditions.
What is the characteristic of soft water?- a)Does not easily form lather with soap
- b)Contains high levels of calcium and magnesium
- c)Readily forms lather with soap
- d)Is always distilled water
Correct answer is option 'C'. Can you explain this answer?
What is the characteristic of soft water?
a)
Does not easily form lather with soap
b)
Contains high levels of calcium and magnesium
c)
Readily forms lather with soap
d)
Is always distilled water
| | Prepworks Coaching answered |
Soft water is characterized by its ability to readily form lather with soap. It typically contains low concentrations of calcium and magnesium ions, which are responsible for hardness in water. This property makes soft water preferable for washing and cleaning applications.
Which of the following is a method to obtain crystals from a saturated solution?- a)Heating a cold solution
- b)Adding more solute
- c)Cooling a hot saturated solution
- d)Mixing with a strong acid
Correct answer is option 'C'. Can you explain this answer?
Which of the following is a method to obtain crystals from a saturated solution?
a)
Heating a cold solution
b)
Adding more solute
c)
Cooling a hot saturated solution
d)
Mixing with a strong acid
| | Aurora Institute answered |
Cooling a hot saturated solution is a common method to obtain crystals. As the solution cools, its ability to hold solute decreases, leading to the formation of solid crystals as the solute precipitates out of solution. This principle is widely used in crystallization processes in chemistry.
What is the meaning of the term "deliquescence"?- a)Absorption of water vapor from the air
- b)Formation of crystals
- c)Loss of water from hydrated crystals
- d)Dissolving in a solvent
Correct answer is option 'A'. Can you explain this answer?
What is the meaning of the term "deliquescence"?
a)
Absorption of water vapor from the air
b)
Formation of crystals
c)
Loss of water from hydrated crystals
d)
Dissolving in a solvent
| | Aurora Institute answered |
Deliquescence refers to the ability of certain substances to absorb moisture from the air, resulting in the substance becoming wet and often dissolving into a solution. This property is observed in substances like calcium chloride, which can absorb enough moisture to form a liquid solution.
What is the primary role of the water cycle?- a)To increase water hardness
- b)To create ice
- c)To regulate temperature
- d)To illustrate the movement and transformation of water in nature
Correct answer is option 'D'. Can you explain this answer?
What is the primary role of the water cycle?
a)
To increase water hardness
b)
To create ice
c)
To regulate temperature
d)
To illustrate the movement and transformation of water in nature
| | Prepworks Coaching answered |
The primary role of the water cycle is to illustrate the continuous movement and transformation of water in nature. It encompasses processes such as evaporation, condensation, precipitation, and runoff, all of which are vital for maintaining ecosystems and supporting life on Earth.
At what temperature does pure water freeze under normal atmospheric pressure?- a)-10°C
- b)0°C
- c)100°C
- d)4°C
Correct answer is option 'B'. Can you explain this answer?
At what temperature does pure water freeze under normal atmospheric pressure?
a)
-10°C
b)
0°C
c)
100°C
d)
4°C
| | Prepworks Coaching answered |
Pure water freezes at 0°C under normal atmospheric pressure (1 atmosphere). This is a crucial temperature point in understanding water's phase changes and its role in the environment, as it influences weather patterns, aquatic life, and ecosystems.
What happens to solubility of most solids as temperature increases?- a)Solubility increases
- b)Solubility decreases
- c)Solubility remains unchanged
- d)Solubility fluctuates
Correct answer is option 'A'. Can you explain this answer?
What happens to solubility of most solids as temperature increases?
a)
Solubility increases
b)
Solubility decreases
c)
Solubility remains unchanged
d)
Solubility fluctuates
| | Prepworks Coaching answered |
For most solids, solubility increases with an increase in temperature. This is important in various applications, including cooking and chemical processes, where higher temperatures can dissolve more solute, resulting in more concentrated solutions.
What is the term for a solution that contains the maximum amount of solute that can be dissolved at a given temperature?- a)Unsaturated solution
- b)Saturated solution
- c)Supersaturated solution
- d)Dilute solution
Correct answer is option 'B'. Can you explain this answer?
What is the term for a solution that contains the maximum amount of solute that can be dissolved at a given temperature?
a)
Unsaturated solution
b)
Saturated solution
c)
Supersaturated solution
d)
Dilute solution
| | Prepworks Coaching answered |
A saturated solution is one that contains the maximum amount of solute that can be dissolved in a solvent at a specific temperature. Any additional solute added will not dissolve and will remain as a precipitate. Understanding the concept of saturation is fundamental in chemistry and various applications like cooking and industrial processing.
What is the significance of water's high specific heat capacity?- a)It helps moderate climate and temperature.
- b)It makes water less effective as a solvent.
- c)It allows water to evaporate quickly.
- d)It increases the boiling point of water.
Correct answer is option 'A'. Can you explain this answer?
What is the significance of water's high specific heat capacity?
a)
It helps moderate climate and temperature.
b)
It makes water less effective as a solvent.
c)
It allows water to evaporate quickly.
d)
It increases the boiling point of water.
| | Prepworks Coaching answered |
Water’s high specific heat capacity means it can absorb a lot of heat without a significant change in temperature. This property helps moderate the climate of nearby land, making areas near large bodies of water experience milder temperatures. It also plays a critical role in regulating temperatures in living organisms.
What is a characteristic of a true solution?- a)Solute particles are large and visible
- b)Solute particles do not settle and cannot be seen
- c)Solute can be separated by filtration
- d)The solution is opaque
Correct answer is option 'B'. Can you explain this answer?
What is a characteristic of a true solution?
a)
Solute particles are large and visible
b)
Solute particles do not settle and cannot be seen
c)
Solute can be separated by filtration
d)
The solution is opaque
| | Aurora Institute answered |
A true solution is characterized by the solute particles being so small that they do not settle and cannot be seen. The solution appears clear and transparent, and light passes through without scattering. This is important in many applications, such as in beverages and pharmaceuticals.
What is the primary reason that water is often referred to as the "universal solvent"?- a)It can dissolve a wide range of substances.
- b)It is the most abundant liquid on Earth.
- c)It can dissolve only solids.
- d)It has a high boiling point.
Correct answer is option 'A'. Can you explain this answer?
What is the primary reason that water is often referred to as the "universal solvent"?
a)
It can dissolve a wide range of substances.
b)
It is the most abundant liquid on Earth.
c)
It can dissolve only solids.
d)
It has a high boiling point.
| | Prepworks Coaching answered |
Water is called the "universal solvent" because it can dissolve a wide variety of substances, including solids, gases, and other liquids. This property is mainly due to its high dielectric constant, which reduces the attraction between positive and negative ions, enabling it to interact with and separate various compounds. This makes water essential for biological processes, as many chemical reactions occur in aqueous solutions.
Which of the following describes the density behavior of water as it freezes?- a)Water contracts and becomes denser
- b)Water becomes more viscous
- c)Water remains the same density
- d)Water expands and becomes less dense
Correct answer is option 'D'. Can you explain this answer?
Which of the following describes the density behavior of water as it freezes?
a)
Water contracts and becomes denser
b)
Water becomes more viscous
c)
Water remains the same density
d)
Water expands and becomes less dense
| | Prepworks Coaching answered |
As water freezes, it expands and becomes less dense, which is why ice floats on water. This unique property of water is crucial for aquatic life during winter, as it allows a layer of ice to form on the surface, insulating the water below and maintaining a habitable environment.
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