Chemistry Semester 2 Chapter 15 Test

-Reverse Osmosis Desalinization Steps:

1. Seawater supply: Seawater moves from the ocean to the desalination plant through large pipes 2. Pretreatment system: Incoming water is treated and filtered to remove debris, sediment, and other microscopic particles 3. Reverse osmosis process: during a process called reverse osmosis, high pressure is used to force the seawater through semi-permeable membranes. These membranes only allow water to pass through, leaving salts and contaminants behind in a concentrated seawater solution, called brine. The brine is then released back into the ocean 4. Post treatment system: the treated water goes through more filters.In addition, chemical disinfectants are usually added 5. Drinking water storage: the treated drinking water is transferred to a tank and stored until needed 6. Drinking water supply: the tap water you drink may have originally come for the sea!!!!

What saying sums up the observation that, as a rule, polar solvents dissolve ionic compounds and polar molecules, but nonpolar solvents dissolve nonpolar compounds?

"like dissolves like"

percent mass of H2O=

(mass of water/mass of hydrate)(100%)

*effloresce:

(of a substance) lose moisture and turn to a fine powder upon exposure to air

Water in the solid state(3):

-hard; does not flow; colorless -hydrogen bonds in hexagons -less dense

Water in the liquid state(3):

-liquid; flows; colorless -hydrogen bonds are irregular -more dense

Vapor pressure is a ...

...measure of the force exerted by the gas above a liquid in a container

Properties of Water(Polar):

1. Universal solvent(can dissolve ionic/ molecular compounds etc.) 2. High surface tension 3. High boiling point 4. Low Vapor pressure 5. At 4C, water is it's most dense and then at OC in the solid phase it is the least dense

Approximately what fraction of Earth's surface is covered in water?

3/4

If enough solvent is present, what will eventually happen to the ionic solid depicted at the bottom of the diagram?

All of the ions will become surrounded by solvent molecules and the ionic solid will disappear into the solution

-A ______ system can be destroyed or coagulated by the addition of electrolytes

Colloidal

*What distinguishes a colloid from a suspension and a solution?

Colloids have particles smaller than those in suspension and larger than those is solutions

How do the properties of colloids differ form those of suspensions and solutions?

Colloids: cloudy or milky in appearance when that are concentrated

What happens to the density of most substances as they cool and solidify?

Density usually increases as a substance cools

*Desiccant(another name for hydroscopic substance):

Desiccants are substances which draw in moisture from their surrounding environment -a dry agent/ a hygroscopic substance used as a drying agent Ex: rice

Why is ice less dense than liquid water?

Ice molecules are arranged in an open, rigid framework. When ice melts, the framework collapses, and the molecules pack closer together.

-Vapor pressure:

Low vapor pressure: hydrogen bonding between water molecules explains this Vapor pressure: the result of molecules escaping from the surface of the liquid and entering the vapor phase

*What factor causes the high surface tension, low vapor pressure, and high boiling point of water?

Many unique and important properties of water-including its high surface tension, low vapor pressure, and high boiling point—result in hydrogen bonding

What does "5H2O" mean when included in a chemical formula

The compound contains five water molecules per formula unit

Will ice float on liquid water?

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. Yes

*Why do hydrates easily lose and regain water?

The forces holding the water molecules in hydrates are not very strong, so the water is easily lost and regained

-How do the polarities of the two 0—H affect the polarity of the molecule?

The shape of the molecule is the determining factor

What happens to dry sodium hydroxide pellets that are exposed to normally moist air? What kind of compound exhibits this behavior?

The sodium hydroxide pellets remove enough water from the air to dissolve completely and form a solution. Sodium hydroxide is an example of a deliquescent compound.

*How can you describe the structure of ice?

The structure of ice is a regular open framework of water molecules in a hexagonal arrangement

The scattering of light in all directions by colloidal particles is known as the ____ _____

Tyndall effect

*Hygroscopic:

a compound that absorbs moisture from the air-out of the atmosphere(not enough to forma solution) Ex: Sodium Chloride

-Hydrate:

a compound that has a specific number of water molecules bound to each formula unit

hydrate:

a compound, typically a crystalline one, in which water molecules are chemically bound(to each formula unit) to another compound or an element.

-Electrolyte:

a compounds that conducts an electric current when it is in an aqueous solution or in the molten state; all ionic compounds are electrolytes, but most covalent compounds are not

-Nonelectrolyte:

a compounds that does not conducts current in aqueous solution or in the molten state Ex: Compounds of carbon-table sugar(sucrose) and the alcohol in rubbing alcohol(2-propanol), are nonelectrolytes

A compound that contains water as an integral part of its crystal structure is called ________

a hydrate

*anhydrous:

a hydrate that no longer contains water Ex: Cobalt II Chloride

-Desiccant:

a hydroscopic substance used a drying agent Ex: Calcium sulfate-solid

-Suspension(heterogenous):

a mixture from which some of the particles settle out slowly upon standing -exhibit the Tyndall effect

-Colloid:

a mixture whose particles are intermediate in size between those is a suspension and a solution Ex: paint/ aerosol sprays/ smoke/ milk

-Solvation:

a process that occurs when an ionic solute dissolves; in solution, solvent molecules surround the positive and negative ions Ex: ionic compounds cannot be solvated-????

-Strong electrolyte:

a solution in which large portion of the solute exists as ions Ex: soluble salts, inorganic acids, and organic bases

-Weak electrolyte:

a solution that conducts electricity poorly because only a fraction of the solute exists as ions Ex: organic acids and bases

-Hygroscopic:

a term describing salts and other compounds that remove moisture form the air Ex:calcium chloride monohydrate

-Surface tension:

an inward force that tends to minimize the surface area of a liquid; it causes the surface to behave as if it were thin skin Ex: water tends to form beads on the surface of a newly waxed car

-Surfactant:

any substance that interferes with the hydrogen boding between water molecules and thereby reduces surface tension; soaps are surfactants Ex: soaps and detergents

Water samples containing dissolved substances are called _______ _________

aqueous solutions

Heterogeneous mixtures in which particles are of intermediate size between those of true solutions and suspensions are called _____

colloids

___________contain particles smaller than those in suspensions but larger than those in solutions

colloids

electrolyte:

conduct nerve impulses

-Anhydrous:

describes a substance that does not contain water

-Deliquescent(adj):

describes a substance that removes sufficient water from the air to form a solution; the solution formed has a lower vapor pressure than that of the wate rin the air Ex: pellets of sodium hydroxide

Hygroscopic substances that remove water from the air are used as drying agents called ______

dessicants

*dissociate:

disappear/ disconnect or separate

-Solute:

dissolved particles in a solution

If a hydrate has a vapor pressure greater than that of the water in the surrounding air, the hydrate will lose water to the air, or ______

effloresce

Because all ionic compounds form ions, all ionic compounds are _________

electrolytes

What types of compounds can carry an electric current in the molten state or in aqueous solution?

electrolytes

t/f: After sodium chloride dissolves in a container of water, the sodium chloride will eventually settle to the bottom of the container if the solution remains undisturbed at a constant temperature

false

t/f: When a suspension of clay particles in water is filtered, both clay and water will pass through the filter paper

false

Solvents and solutes my be ____, _____, or ____

gases, liquids, or solids

Both liquid water and solid water have hydrogen bonds, but in solid water, they form a(n) _______ arrangement

hexagonal

-Aqueous solutions:

homogenous mixtures

The water molecules in _____ are easily gained or lost because they are held in place by weak bonds

hydrates

Many of the unique properties of water result from the ______ bonding between water molecules.

hydrogen

-What factor causes the high surface tension, low vapor pressure, and high boiling point of water?

hydrogen bonds

similar?

hydrogen bonds; colorless

When a compound cannot be solvated to any significant extent, it is called _____

insoluble

_______ compounds and polar covalent compounds dissolve most readily in water

ionic

*What types of substances dissolve most readily in water?

ionic compounds and polar covalent compounds.

Bonds:

ionic, covalent, metallic

-Colloidal particles tend to stay suspended because they become charged by absorbing ____ form the dispersing medium onto their surface

ions

ice

less dense than the liquid phase

-Molecular compounds of ____ molar mass are usually gases or liquids with ___ boiling points at normal atmospheric pressure

low...low -Ammonia has molar mass of 17.0 g/mol and boils at about -33C -Water has a molar mass of 18.0 g/mol, but it has a boiling point of 100C

-Adsorption:

means to adhere to a surface

Do liquids that have higher surface tension produce drops that are flatter or more nearly spherical than liquids with lower surface tension?

nearly spherical

Compounds that do not conduct an electric current in either aqueous solution or the molten state are called _________

nonelectrolytes

Tyndall effect:

scattering of light by particles in a colloid or suspension, which causes a beam of light to become visible-suspensions also exhibit the Tyndall effect, solution do not because particles in solutions are too small to scatter

dissolved particles:

solute

A solvent dissolves the _____, and the ____ becomes dispersed in the _____.

solute... solute...solvent

homogeneous mixture of particles in a dissolving medium:

solution

largest to smallest: colloid, solution, suspension?

solution, colloid, suspension???

What process occurs when solute ions become surrounded by solvent molecules?

solvation

dissolving medium:

solvent

What is the name for an agent, such as a detergent, that has the ability to reduce surface tension?

surfactant

The particles in a(n) ______ are relatively large and will settle out over time

suspension

Heterogeneous mixtures in which particles settle out upon standing are called _____

suspensions

Brownian motion(Scottish botanist Robert Brown):

the chaotic movement of colloidal particles, causes by collision with particles of the solvent in which they are dispersed

Emulsion:

the colloidal dispersion of one liquid in another Ex: Mayonnaise is an example of a colloidal system called an emulsion Ex: oils and greases are not soluble in water but they readily from a colloidal dispersion of soap or detergent is added to the water

-Solvent:

the dissolving medium in a solution

*What is the difference between a suspension and a solution?

the particles of a suspension are much larger and do not stay suspended indefinitely

*Why are all ionic compounds electrolytes?

they dissociate into ions

-Effloresce:

to lose water of hydration; the process occurs when the hydrate has a vapor pressure higher than that of water vapor in the air Ex: copper(II) sulfate pentahydrate

t/f : Heterogeneous mixtures are not true solutions

true

t/f: All ionic compounds are electrolytes

true

The unique properties of water include its low _____ ______ and it high surface tension and boiling point

vapor pressure

What unique substance is essential to all life on Earth?

water

explain why a water drop has surface tension:

water molecules at the surface cannot form hydrogen bonds with air molecules, molecules on the surface are drawn into the body of liquid. The inward pull on the molecules is surface tension

-Water of hydration:

water molecules that are an integral part of a crystal structure

Water in a crystal that is an integral part of the crystal structure is called _____________

water of hydration

-Aqueous solution:

water that contains dissolved substance

*deliquescent:

will draw out so much water that it will become a solution Ex: solidum hydroxide

Polar molecules:

-attracted to one another by dipole interactions -Some polar peculiar compounds are nonelectrolytes in the pure state but because electrolytes when they dissolve in water Ex: neither ammonia nor hydrogen chloride is an electrolyte in the pure state.

Density of a. liquid water at _________ b. liquid water at __________ c. ice at ___________

-4°C1.000 g/cm3 -0°C 0.9998 g/cm3 - 0°C 0.9168 g/cm3

true about hydrated compounds(3):

-Crystals of copper sulfate pentahydrate always contain five molecules of water for each copper and sulfate ion pair -Heating blue crystals of copper sulfate pentahydrate above 100°C drives off the water of hydration, leaving a white anhydrous powder -It is possible to regenerate copper sulfate pentahydrate by treating anhydrous copper sulfate with water

Pros of Reverse Osmosis Desalinization:

-Expands drinking water resources -Low environmental impact-uses minimal chemicals -Low start-up costs

Cons of Reverse Osmosis Desalinization:

-High energy consumption -Low efficiency -Potentially harmful to sea life

Describes a result of the surface tension of water(3)

-In a full glass of water, the water surface seems to bulge over the rim of the glass -Water forms nearly spherical drops at the end of an eyedropper -An insect called a water strider is able to "walk" on water

True concerning water molecules(2):

-In a water molecule, the less electronegative hydrogen atoms acquire a partial positive charge and the oxygen atom acquires a partial negative charge. -Because the water molecule has an H—O—H bond angle of 105°, the molecule as a whole is polar

true about aqueous solutions(3):

-Solute particles can be either ionic or molecular, and their average diameters are usually less than 1 nanometer. -When a solution is filtered, both solute and solvent will pass through the filter paper. -Ionic compounds and substances containing polar covalent molecules readily dissolve in water

best explains why the ionic compounds barium sulfate (BaSO4) and calcium carbonate (CaCO3) are nearly insoluble in water

-The attractions between the ions in the crystals of these ionic compounds are stronger than the attractions between the ions and water molecules

-Water molecules(2):

-are in continuous motion because they have kinetic energy -are polar