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Questions and Answers
Which of the following ions contributes to water hardness?
Which of the following ions contributes to water hardness?
Temporary hardness can be removed by boiling the water.
Temporary hardness can be removed by boiling the water.
True
What is the formula for calculating total hardness in water?
What is the formula for calculating total hardness in water?
CaCO3
Hard water can cause poor detergent performance, leading to residues known as ______.
Hard water can cause poor detergent performance, leading to residues known as ______.
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Match the type of water hardness with its cause:
Match the type of water hardness with its cause:
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What is the primary method for removing permanent hardness in water?
What is the primary method for removing permanent hardness in water?
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Calcium and magnesium chlorides are responsible for temporary hardness in water.
Calcium and magnesium chlorides are responsible for temporary hardness in water.
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What effect does hard water have on diesel engines?
What effect does hard water have on diesel engines?
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What is the main cause of corrosion in ship boilers due to hard water?
What is the main cause of corrosion in ship boilers due to hard water?
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Sea water is classified as soft water.
Sea water is classified as soft water.
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What is the preferred type of water for cooling diesel engines with permanent hardness?
What is the preferred type of water for cooling diesel engines with permanent hardness?
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The scale formed in boilers can reduce the ______ efficiency by impairing the flow of heat.
The scale formed in boilers can reduce the ______ efficiency by impairing the flow of heat.
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Match the water hardness classifications with their respective ranges:
Match the water hardness classifications with their respective ranges:
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Which of the following methods is NOT a water softening technique?
Which of the following methods is NOT a water softening technique?
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The soda-lime method uses lime and soda to remove hardness from water by precipitation.
The soda-lime method uses lime and soda to remove hardness from water by precipitation.
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What is the general measurement unit for determining water hardness?
What is the general measurement unit for determining water hardness?
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Which of the following correctly describes the polarity of water?
Which of the following correctly describes the polarity of water?
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Water has a neutral pH of 7.5.
Water has a neutral pH of 7.5.
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What is the significance of water's high specific heat?
What is the significance of water's high specific heat?
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Water contracts until _____ °C before it starts to expand upon freezing.
Water contracts until _____ °C before it starts to expand upon freezing.
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Match the following water properties with their effects:
Match the following water properties with their effects:
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Which of the following substances will increase the electrical conductivity of water?
Which of the following substances will increase the electrical conductivity of water?
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Water is the only natural substance that can exist in all three states of matter on Earth.
Water is the only natural substance that can exist in all three states of matter on Earth.
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What is the impact of ice forming on the surface of lakes?
What is the impact of ice forming on the surface of lakes?
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Study Notes
Water Properties
- Water is a polar molecule with hydrogen bonding, which leads to unique properties.
- It's a universal solvent.
- Water exhibits cohesion behaviour (high surface tension).
- It has a high heat of vaporization.
- Water's density is highest at 4°C (it expands upon freezing).
- It resists temperature changes.
- Water has a neutral pH (7-7.5).
- Water has a high specific heat (c (J/g.°C)).
- Water can dissolve many compounds due to its polarity.
- Biochemical reactions often take place in water by dissolving.
Seawater Properties
- Seawater is a significant substance on Earth.
- Oceans absorb and reflect sunlight.
- They store and transport heat and impact climate systems.
- Oceans are the primary source of atmospheric water vapor.
- Oceans exchange gases (e.g., CO2) with the atmosphere.
- Average seawater density at the surface is 1.027 g/mL (denser than pure water).
- Salinity of seawater is about 3.5% (35 g/L).
- Freezing point of seawater is approximately -2°C (decreases with rising salinity).
- Seawater has the highest surface tension among liquids.
- The color of the ocean is blue because it absorbs other colors and reflects blue light most.
Seawater Composition
- Contains more dissolved ions than other water types (2.5% salts).
- Contains dissolved gases (nitrogen, oxygen, carbon dioxide).
- Provides nutrients for marine life.
- Salinity is the saltiness or dissolved salt content in water.
- Salinity ranges between 3.1% and 3.8% but not uniformly.
- Variations in ocean salinity due to evaporation and precipitation.
Water Hardness
- Water hardness measures dissolved minerals (primarily calcium (Ca²⁺) and magnesium (Mg²⁺)).
- High mineral content indicates hard water.
- Limestone (CaCO₃) and gypsum (CaSO₄·2H₂O) are common sources of these minerals.
- Dissolved calcium and magnesium increase hardness.
- Hard water can be harmful in industrial applications.
- Hardness is measured in ppm (mg/L) of calcium carbonate.
Types of Hardness
- Temporary Hardness (Carbonate Hardness): Caused by dissolved bicarbonate minerals (HCO₃⁻). When heated, this hardness can be removed by boiling.
- Permanent Hardness (Noncarbonate Hardness): Caused by dissolved sulphates and chlorides of calcium and magnesium. This type of hardness cannot be removed by boiling.
Effects of Hard Water
- Hard water forms deposits called "scale".
- Scale can impede heat transfer in boilers, leading to overheating.
- Hard water can cause poor detergent/soap performance, forming residues.
- Can cause corrosion in boilers and other equipment, leading to reduced efficiency and potential damage.
Water Softening Methods
- Water softening removes or reduces calcium, magnesium, and other metal cations.
- Soda-lime method (precipitation process): Uses lime (Ca(OH)₂) and soda (Na₂CO₃) to precipitate out the hardness ions.
- Ion exchange resins: Use a resin to exchange the calcium and magnesium with sodium ions. This is a common method in households and industries.
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Description
Test your knowledge on the unique properties of water and seawater. This quiz covers topics such as water's molecular structure, its role as a solvent, and the significance of seawater in Earth's climate. Explore how these properties influence various biochemical reactions and environmental processes.
