Water and Aqueous Systems Chapter 15 Chemistry

The Tyndall effect refers to the scattering of light in all directions by colloidal particles. This phenomenon occurs when light passes through a heterogeneous mixture, such as a colloidal solution, and gets scattered by the particles present in it. The scattering of light is more pronounced in colloidal systems compared to true solutions, where the particles are much smaller and do not scatter light significantly. Therefore, the correct answer is Tyndall effect.

The saying "like dissolves like" summarizes the observation that polar solvents tend to dissolve ionic compounds and polar molecules, while nonpolar solvents dissolve nonpolar compounds. This means that substances with similar polarity or solubility characteristics tend to dissolve each other. Polar solvents have a partial positive and negative charge, allowing them to interact with ions and polar molecules. Nonpolar solvents lack these charges and are better suited for dissolving nonpolar compounds. Therefore, the saying highlights the importance of matching the polarity of solvents and solutes for effective dissolution.

A solution is a homogeneous mixture in which particles of a solute are evenly distributed and dissolved in a solvent. This means that the solute particles are uniformly spread throughout the solvent, resulting in a uniform composition and appearance. The solute is the substance that is being dissolved, while the solvent is the medium in which the solute is dissolved. Therefore, a solution is a correct answer as it accurately describes the characteristics of a homogeneous mixture of particles in a dissolving medium.

Desiccants are substances that have the ability to remove water from the air. They are commonly used as drying agents in various applications. Copper sulfate pentahydrate is an example of a desiccant. It has a strong affinity for water molecules and can effectively absorb moisture from the surrounding environment. Therefore, desiccants like copper sulfate pentahydrate are used to keep products dry and prevent moisture-related damage.

Colloids are heterogeneous mixtures in which particles are of intermediate size between those of true solutions and suspensions. In colloids, the particles are larger than those in a solution but smaller than those in a suspension. These particles do not settle down over time and remain dispersed throughout the mixture. Examples of colloids include milk, fog, and gelatin.

Water is the unique molecular compound that is the foundation of all life on Earth. It is essential for various biological processes and is a universal solvent, allowing for the transportation of nutrients and waste in living organisms. Water also has unique properties such as high specific heat, which helps regulate temperature in organisms, and its ability to exist in all three states (solid, liquid, and gas) at Earth's temperature range, making it crucial for sustaining life.

The notation ".5H2O" in a chemical formula indicates that there are five water molecules per formula unit of the compound.

The high specific heat capacity of water is due to the hydrogen bonding. Hydrogen bonding occurs when the positive hydrogen atom of one water molecule is attracted to the negative oxygen atom of another water molecule. This bonding creates strong intermolecular forces, resulting in a high amount of energy required to change the temperature of water. As a result, water can absorb and store a large amount of heat without experiencing a significant temperature change, making it an excellent regulator of temperature in various environments.

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The water molecule has an H-O-H bond angle of 105°, which is less than the ideal tetrahedral angle of 109.5°. This distortion in the bond angle causes an uneven distribution of electron density in the molecule, resulting in a polar molecule. The oxygen atom attracts the shared electrons more strongly than the hydrogen atoms, creating a partial negative charge on the oxygen and partial positive charges on the hydrogen atoms. This polarity allows water molecules to form hydrogen bonds with each other and other polar molecules, giving water its unique properties such as high boiling point, surface tension, and solvent capabilities.

Electrolytes are compounds that can carry an electric current in the molten state or in aqueous solution. This is because electrolytes dissociate into ions when dissolved in water or melted, allowing the movement of charged particles. Water itself is a solvent that can facilitate the dissociation of electrolytes, but it is not an electrolyte on its own.

Nonelectrolytes are compounds that do not conduct an electric current in either aqueous solution or the molten state. This means that they do not dissociate into ions when dissolved in water or melted. Unlike electrolytes, which dissociate into ions and allow for the flow of electric current, nonelectrolytes do not contain charged particles and therefore cannot conduct electricity.

A compound that contains water as an integral part of its crystal structure is called a hydrate. This means that water molecules are chemically bonded to the compound, forming a stable structure. Hydrates are often formed when a compound crystallizes from a solution containing water. The water molecules can be removed from the hydrate through heating, resulting in a dehydrated compound. Therefore, the correct answer is a hydrate.

In a solution, the solute refers to the substance that is dissolved in the solvent. The solute can be a solid, liquid, or gas, and it is the component that is present in a smaller amount. The solvent, on the other hand, is the substance in which the solute is dissolved, and it is usually present in a larger amount. Therefore, in the given context, "dissolved particles" can be referred to as solute because they are the substances that are dissolved in a solution.

A surfactant is an agent that has the ability to reduce surface tension. Surface tension is the force that holds the molecules of a liquid together and causes it to form droplets. Surfactants work by disrupting the cohesive forces between the liquid molecules, allowing it to spread more easily on a surface or mix with other substances. Detergents are a common example of surfactants, as they are used to remove dirt and grease by reducing the surface tension of water and allowing it to penetrate and lift away the contaminants.

Solvation is the process that occurs when solute ions become surrounded by solvent molecules. Solvation involves the attraction between the solute particles and the solvent particles, resulting in the solute particles being dispersed and surrounded by the solvent molecules. This process is important in dissolving solutes in a solvent and forming a homogeneous solution.

The given sentences describe the results of the surface tension of water. Surface tension is the property of water that allows it to form a "bulge" over the rim of a glass and form nearly spherical drops. The ability of a water strider to walk on water is also a result of surface tension. Detergent molecules can strengthen hydrogen bonding between water molecules, which affects the surface tension.

The term "dissolving medium" refers to the substance in which another substance is dissolved. In this context, the correct answer is "solvent" because a solvent is a substance that has the ability to dissolve other substances, forming a solution. Therefore, the solvent is the dissolving medium in a solution.

Oil spills cause environmental problems because the insoluble oil spreads out across the water. As it spreads, it can come into contact with plants and animals. Oil clogs pores and does other damage to the life cycle of living organisms.

Approximately three-fourths or 3/4 of Earth's surface is covered in water. This is a well-known fact supported by scientific research and observations. The Earth's surface is predominantly covered by oceans, seas, lakes, and rivers, which contribute to a significant portion of the planet's overall surface area. This answer is widely accepted and acknowledged in the field of geography and earth sciences.

Water samples containing dissolved substances are called aqueous solutions because the term "aqueous" refers to a solution in which water is the solvent. In this case, water is the solvent and the dissolved substances are the solute. Aqueous solutions are commonly encountered in various fields such as chemistry, biology, and environmental science. They play a crucial role in many chemical reactions, biological processes, and natural phenomena.

In a water molecule, the less electronegative hydrogen atoms acquire a slight positive charge and the oxygen atom acquires a slight negative charge. This is due to the unequal sharing of electrons between the oxygen and hydrogen atoms in the water molecule. The oxygen atom is more electronegative than the hydrogen atoms, causing it to attract the shared electrons more strongly. As a result, the oxygen atom becomes slightly negative, while the hydrogen atoms become slightly positive. This polarity of the water molecule allows it to form hydrogen bonds with other water molecules, giving water its unique properties.

As most substances cool and solidify, the molecules within them slow down and come closer together. This results in an increase in the density of the substance. Therefore, density usually increases as a substance cools.

The given correct answer for the question is 1.000 g/cm3. This is the density of liquid water at 4 °C. Density is defined as the mass per unit volume of a substance. The density of water is highest at 4 °C, which means that 1 cm3 of water at this temperature has a mass of 1.000 grams.

Hydrated compounds are compounds that contain water molecules within their crystal structure. The given statement is true for hydrated compounds because the crystals of copper sulfate pentahydrate always contain five molecules of water for each copper and sulfate ion pair. When these crystals are heated above 100°C, the water of hydration is driven off, resulting in a white anhydrous powder. Additionally, it is possible to regenerate copper sulfate pentahydrate by treating anhydrous copper sulfate with water. Therefore, the statement holds true for hydrated compounds.

When dry sodium hydroxide pellets are exposed to normally moist air, they absorb enough water from the air to dissolve completely and form a solution. This behavior is exhibited by deliquescent compounds, such as sodium hydroxide.

Solvents and solutes can indeed be gases, liquids, or solids. Solvents are substances capable of dissolving other substances, and they can exist in any of the three states of matter. Similarly, solutes are the substances that are dissolved in solvents, and they can also be in any of the three states of matter. Therefore, it is true that solvents and solutes may be gases, liquids, or solids.

Suspensions are heterogeneous mixtures in which particles settle out upon standing. This means that the particles in a suspension are not evenly distributed throughout the mixture and will eventually separate and settle at the bottom. Colloids, on the other hand, are also heterogeneous mixtures but the particles do not settle out upon standing. Therefore, suspensions fit the description given in the question.

The explanation for the correct answer is that the amount of heat given off during the condensation of one gram of water is equal to the amount of heat absorbed by one gram of water when it vaporizes. This is because the process of condensation involves the conversion of water vapor into liquid water, releasing heat in the process. Conversely, when water vaporizes, it absorbs heat from the surroundings to break the hydrogen bonds between water molecules and convert it into vapor. The extensive network of hydrogen bonds in liquid water is responsible for holding the molecules together, contributing to its high boiling point and heat absorption/release during vaporization/condensation.

The given statement "When a solution is filtered, both solute and solvent will pass through the filter paper" is false. When a solution is filtered, the solute particles are usually larger than the pores in the filter paper and therefore get trapped, while the smaller solvent particles pass through the filter paper. This is why the correct answer is "True about aqueous solutions."

When a solid crystal of sodium chloride is placed in water, water molecules collide with the crystal and attract its Na+ and Cl- ions. This is due to the polar nature of water molecules, with the oxygen atom being slightly negative and the hydrogen atoms being slightly positive. This polarity allows water molecules to form hydrogen bonds with the charged ions in the crystal, causing them to dissociate and become surrounded by water molecules in a process called hydration.

If a hydrate has a vapor pressure greater than that of the water in the surrounding air, it means that the hydrate has a higher tendency to release water molecules into the air. This process is known as efflorescence. Therefore, the correct answer is "effloresce".

Liquid water at 0°C has a density of 0.9998 g/cm3. Density is defined as the mass of a substance per unit volume. This means that for every cubic centimeter of liquid water at 0°C, it has a mass of 0.9998 grams.

Water molecules are held together by hydrogen bonds, which are relatively strong intermolecular forces. When water evaporates or vaporizes, these hydrogen bonds need to be broken, requiring energy in the form of heat. As a result, water absorbs a large amount of heat during the process of evaporation or vaporization. Therefore, the given statement is true.

A sphere has the smallest surface area for a given volume because it is a three-dimensional shape with the least amount of surface area compared to other shapes. The sphere's surface area is minimized due to its symmetrical nature, where every point on the surface is equidistant from the center. This results in a compact shape that encloses the maximum volume with the least amount of surface area, making it the most efficient shape in terms of minimizing surface area.

When a suspension of clay particles in water is filtered, the clay particles will not pass through the filter paper. The filter paper acts as a barrier that traps the clay particles and allows only the water to pass through, resulting in a filtrate that is free of clay particles. Therefore, the statement is false.

The correct answer explains that the attractions between the ions in the crystals of barium sulfate and calcium carbonate are stronger than the attractions between the ions and water molecules. This means that the ions in the crystals are tightly held together, making it difficult for them to separate and dissolve in water.

The evaporation and condensation of water play a crucial role in regulating regional temperatures on Earth. In the tropics, water absorbs heat while evaporating from the surfaces of surrounding oceans. This absorption of heat helps to cool down the surrounding areas, preventing temperatures from becoming too high. On the other hand, in polar regions, water releases heat while condensing out of the air. This release of heat helps to warm up the cold polar regions, preventing temperatures from becoming too low. Therefore, without the evaporation and condensation of water, temperatures in the tropics would be much higher, while temperatures in polar regions would be much lower.

The correct answer is that the density of liquid water decreases from 4 °C to 0 °C, and ice at 0 °C is less dense than liquid water at 0 °C. This means that ice will float on liquid water.

This answer correctly describes a property of detergents. Detergents act as "wetting agents" by reducing the surface tension of water. This interference with the hydrogen bonding between water molecules allows the water to spread out instead of forming beads.

After sodium chloride dissolves in a container of water, the sodium and chloride ions separate and become evenly distributed throughout the solution. This process is called dissociation. The ions are surrounded by water molecules, forming a hydrated ion. Due to the random motion of water molecules, the ions are constantly moving and colliding with each other. This prevents the sodium chloride from settling to the bottom of the container. Therefore, the statement is false.

Water in a crystal that is an integral part of the crystal structure is called water of hydration. This means that the water molecules are incorporated into the crystal lattice, forming bonds with the other atoms or ions in the crystal. These water molecules are not easily separated from the crystal and are essential for maintaining the crystal's structure. This is different from ice crystals, which are formed when water freezes and the water molecules arrange themselves in a specific pattern. Water of hydration is also different from non conductive, as it can still conduct electricity due to the presence of ions in the crystal lattice.

The statement "Heterogeneous mixtures are not true solutions" is true. Heterogeneous mixtures are composed of different substances that are not uniformly distributed throughout the mixture. On the other hand, true solutions are homogeneous mixtures where the solute particles are evenly dispersed in the solvent particles. Therefore, heterogeneous mixtures cannot be considered true solutions.

Surface tension is a phenomenon that occurs due to the cohesive forces between the molecules of a liquid. In the case of water, these cohesive forces are primarily hydrogen bonds. The given answer correctly states that water molecules at the surface cannot form hydrogen bonds with air molecules. As a result, the molecules on the surface are drawn into the body of the liquid, creating an inward pull or tension. This cohesive force between water molecules at the surface is what we refer to as surface tension.

Water has a higher boiling point compared to other compounds due to hydrogen bonding. Hydrogen bonding occurs between the hydrogen atoms of one water molecule and the oxygen atom of another water molecule. These hydrogen bonds create strong attractions between water molecules, requiring more heat energy to break them and reach the boiling point.

When ice melts, the framework collapses, and the molecules pack closer together. This is because in the solid state, the water molecules in ice form a crystal lattice structure held together by hydrogen bonds. When heat is applied and the ice melts, the hydrogen bonds break and the water molecules become more mobile. As a result, the molecules can move closer together, increasing the density of the water.

Liquids with higher surface tension tend to minimize their surface area, causing them to form more nearly spherical drops. This is because surface tension is the force that causes the surface of a liquid to behave like a stretched elastic sheet. The molecules at the surface of the liquid are pulled inward, creating a tension that tries to minimize the surface area. As a result, the liquid droplets formed by liquids with higher surface tension are more nearly spherical in shape.

A large body of water moderates the temperature by keeping it cooler during the day and warmer at night. This is because water has a higher specific heat capacity than land, meaning it can absorb and store more heat energy. During the day, the water absorbs heat from the sun and keeps the surrounding air cooler. At night, the water releases the stored heat, keeping the air warmer. This moderating effect helps to create more stable and comfortable temperatures in areas near large bodies of water.

In the model of solvation, as more solvent is added, the solvent molecules surround the ions of the ionic solid. Eventually, all of the ions will become surrounded by solvent molecules as the surface of the ionic solid disappears into the solution.

Iron does not require nearly 10 times more heat than an equal mass of liquid water to produce the same temperature increase. This statement is false because the specific heat capacity of iron is actually lower than that of water. This means that iron requires less heat to produce the same temperature increase compared to an equal mass of liquid water.