Chem 135- weeks 3 and 4

Saturdated solution

A solution that contains the maximum amount of dissolved solute at a given temperature is said to be

A sample of water in a closed container is at equilibrium at room temperature. What will happen to the amount of water in the liquid phase, the amount of water in the gas phase, and the vapor pressure when the sample is placed in the refrigerator?

Before the sample is refrigerated, the rate of evaporation equals the rate of condensation. As the sample cools, though, the rate of vaporization will decrease compared with the rate of condensation. This will cause the amount of water in the gas phase to decrease, which will lower the vapor pressure. The amount of water in the liquid phase will increase. Eventually, a new equilibrium will be established at a lower vapor pressure.

Miscible

Describes two liquids that are soluble in each other infinitely. Liquids that have the same type of intermolecular forces between their molecules, such as water and ethanol, which both form hydrogen bonds, are usually miscible.

vapor-pressure lowering, ΔP,

. Thus, if you add a solid solute to the liquid, its vapor pressure will decrease. The vapor-pressure lowering, ΔP, depends on the concentration of the solute particles, but not on their identity. Substances that evaporate easily, and thus have a measurable vapor pressure, have relatively weak intermolecular forces and are said to be volatile (Chapter 12). Most liquid solvents, such as water, are volatile. Solid solutes, on the other hand, are nonvolatile, meaning they do not easily vaporize and therefore do not contribute to the vapor pressure of the solution

capillary action

1. Cohesion is the attraction of atoms and molecules to like particles. Thus, water and mercury exhibit strong cohesion because they have strong intermolecular forces. 2. Adhesion, the attraction to different particles, is also possible, provided the other particle can form similar intermolecular forces. Water exhibits adhesion to other hydrogen bonding materials, for example, which is why paper towels work so well at cleaning up spilled water. Paper is composed of cellulose, which contains many, many O-H bonds capable of hydrogen bonding with water molecules.

Identify the phase change described by the following equations. C18H38(s) → C18H38(l) CO2(g) → CO2(s) NH3(l) → NH3(g)

1.The transition from a solid to a liquid is called melting or fusion. 2.The transition from a gas directly to a solid is called deposition. 3.The transition from a liquid to a gas is called vaporization to form gases.

How do we know genetic information can be transmitted between two strains of bacteria

1928 Fredrick Griffith mice pneumonia experiment. Mixing dead virulent bacteria with live non viral wny bacteria transmitted the dead dna to the live bacteria and killed the mouse. Leading us to their second experiment when unveiled the genetic information is stored in the Rnase

The enthalpy of fusion of water

6.01 kJ/mol and the enthalpy of vaporization of water is 40.7 kJ/mol. When the enthalpies of fusion, vaporization, and sublimation are given in kilojoules per mole, the product of the enthalpy, ∆H, and the amount of substance in moles, n, gives the heat change, q, in kilojoules: q=N(deltaH)

unsaturated solution

If the solution contains less than the maximum amount of solute, it is

recrystallization

If you have a saturated solution of a solid solute at a high temperature and you lower the temperature of the solution, the solvent will be unable to hold that much solute in solution, and the excess solute will normally crystallize from the solution as the temperature is lowered. At 100°C, for example, the solubility of H3BO3 in water is 27.53 g per 100 g of water. If a solution containing 27.53 g of H3BO3 in 100 g of water at 100°C is cooled to 30°C, then only 6.35 g of the H3BO3 will continue to be soluble, and 21.18 g of H3BO3 will crystallize from the solution. This type of process, called

examples of phase

Solid in solid -Brass, a mixture of zinc and copper (Figure 13.1) Solid in liquid -Sugar water Liquid in solid-Mercury in silver (dental amalgam) Liquid in liquid- Gasoline (a mixture of hydrocarbons) Gas in solid -Hydrogen in platinum Gas in liquid -Carbonated soft drinks (CO2 in water) Gas in gas- Air (O2 in N2)

Sublimation

Solids that enter the gas state directly do so by. opposite is deposition.

phase changes

Substances change phases by adding or subtracting energy

meniscus forms

The forces of cohesion and adhesion explain the formation of a meniscus when liquid is poured into narrow-diameter containers such as graduated cylinders. Liquids such as water that are attracted to the glass or plastic of the cylinder and have a high surface tension exhibit a concave meniscus (Figure 12.13a), while liquids such as mercury that have no cohesion to the cylinder but high surface tension exhibit a convex meniscus (Figure 12.13b). Liquids with low surface tension appear to have a flat surface in a graduated cylinder.

vapor pressure lowering

The lowering of vapor pressure of a solvent by the addition of a nonvolatile solute to the solvent.

Vaporization

The process of changing a liquid to a gas is called. opposite is called condensation.

mole fraction

The ratio of the moles of solute in solution to the total number of moles of both solvent and solute

N2, HF, and HBr can be liquids under the right conditions of temperature and pressure. Rank their surface tensions from lowest to highest.

The strength of the intermolecular forces determines the surface tension. Start by determining the predominant intermolecular force for each molecule: N2 is nonpolar and interacts with other N2 molecules via dispersion forces. HF is a strongly polar molecule that forms hydrogen bonds. HBr is polar and will interact with other HBr molecules via dipole-dipole forces but not hydrogen bonds. Since dispersion is the weakest intermolecular force, N2 will have low surface tension as a liquid. Since hydrogen bonding is the strongest of the intermolecular forces in these examples, HF will have high surface tension as a liquid. The ranking is N2 < HBr < HF.

fusion

The transition from the solid phase to the liquid phase, commonly called melting, is also referred to as. opposite is freezing.

Weak intermolecular forces what vapor pressure trend?

The weaker the intermolecular forces the higher potential for a higher vapor pressure at a temperature.

Origin of Surface Tension in a Liquid

Particles in the middle of a liquid experience intermolecular attractions in all directions, resulting in no net attraction in any direction. Particles at the surface experience a net downward or net inward attraction, causing liquids to minimize their surface area.

electron sea model

Proposes that all metal atoms in a metallic solid contribute their valence electrons to form a "sea" of electrons, and can explain properties of metallic solids such as malleability, conduction, and ductility.more complete model, called band theory, describes the valence electrons as existing in delocalized, overlapping orbitals (Section 7.5) that extend throughout the metal solid.

There are four types of crystalline solids

determined by the type of particle and bonding between the particles: molecular, ionic, covalent-network, and metallic.

molarity and molality

differ in two ways: For molality, (1) mass is used in the denominator instead of volume and (2) the amount of solvent is measured, rather than the total amount of solution

Volatile substances can be separated from a liquid-phase mixture using

distillation.

The energy change for the vaporization of 1 mole of a liquid is referred to as the

enthalpy of vaporization, ∆Hvap. Similarly, the enthalpy of fusion, ∆Hfus, and enthalpy of sublimation, ∆Hsub, refer to the energy changes associated with the melting and sublimation, respectively, of one mole of a substance. These enthalpy changes (Section 10.7) are sometimes referred to as heats of vaporization, fusion, and sublimation.

Percent by mass is also the number of

grams of solute in exactly 100 g of solution. Unlike molarity (Section 9.5), the denominator of this ratio is a mass, not a volume.

In order from strongest to weakest, the intermolecular forces

ion-dipole, hydrogen bonding, dipole-dipole, and Van der Waals forces.

Step 3 in the dissolution process (solvation)

is exothermic—it releases energy, E, as indicated by the downward-pointing arrow. If the energy released in the solvation step is greater than the sum of the energies absorbed in steps 1 and 2, then the overall enthalpy of solution, ∆Hsol, will be exothermic. If the energy released in the solvation step is less than the sum of the two endothermic steps, however, then the enthalpy of solution will be endothermic. Figure 13.3 shows the case where ∆Hsol is exothermic. Note that when the solvent is water, the heat of solution is called the hydration energy, also known as the enthalpy of hydration.

lattice energy

lattice energy, ∆HL, of an ionic solid is the amount of energy given off when the solid compound forms from ions in the gas phase (Section 10.10). To dissolve an ionic compound, an amount of energy equal to the lattice energy must be added to the system to overcome the ionic attractions and separate the ions in solution.

at the same temperature, substances with stronger intermolecular forces are

less volatile than are substances with weaker intermolecular forces. As a result, substances with stronger intermolecular forces have lower vapor pressures because fewer molecules are in the gas phase above the liquid.

Immiscible

liquids that are not soluble in each other. when two liquids have very different intermolecular forces between their particles and do not dissolve in one another, such as nonpolar oil and highly polar water, the two liquids are said to b

Clausius-Clapeyron equation

ln(p1/p2)=(-ΔHvap/R)(1/T2-1/T1) relationship between vapor pressure and temperature is exponential.

percent by mass

mass of solute/mass of solution x 100

density

mass/volume but also molar mass if grams mass over moles. M=m/n therefore D=PM/RT

solvation

means the same thing as hydration, but it applies to any solvent, not just water. For a solution to form, three processes must occur: (1) the intermolecular forces between solute particles must be broken, (2) the intermolecular forces between solvent particles must be broken, and (3) new intermolecular forces must form between the solute and solvent particles during solvation. The overall energy change, known as enthalpy of solution, ∆Hsol (Section 10.5), is the sum of these three steps, Steps 1 and 2 are endothermic—they require an input of energy, E, as indicated by the upward-pointing arrows.

The heat of vaporization of a substance can be calculated from

measurements of vapor pressure at two different temperatures.

ionic compounds dissolve in water due to the formation of ion-dipole forces between the charged ions and the polar water molecules (Section 12.1). The solvent molecules generally

must be polar (Section 7.2) to be able to exert significant attractions on the charged ions in a way that solvents with nonpolar molecules cannot. In fact, nonpolar solvents are more apt to dissolve nonpolar solutes. The general rule is that "like dissolves like." That is, polar solvents are more likely to dissolve ionic and polar covalent solutes, whereas nonpolar solvents are more likely to dissolve nonpolar covalent solutes.

Transitions from gas to liquid (condensation), liquid to solid (freezing), and gas to solid (deposition) have

negative enthalpy values (they are exothermic).

Molality is the

number of moles of solute per kilogram of solvent, whereas molarity is the number of moles of solute per liter of solution.

An ionic substance is composed

of individual positive and negative ions that form a three-dimensional lattice. The attraction of one ion is not limited to any single other ion but extends to all the oppositely charged ions around it. Thus, the attractive forces throughout the lattice are strong, which makes the structure hard to break up. Ionic substances are solids at room temperature.

colligative properties

of solutions are properties that depend on the concentration of solute particles in the solution but do not depend on what those particles are. The four colligative properties covered in this chapter are vapor-pressure lowering, freezing-point depression, boiling-point elevation, and osmotic pressure.

When a salt dissolves in water, the H2O molecules

orient their dipoles around the cations and anions so that their oppositely charged ends are adjacent to each ion

The concentration of a gas dissolved in a liquid is directly proportional to the

partial pressure of the gas above the liquid (Henry's law, Equation 13.1). If a gas is supersaturated in a solution, the gas will slowly escape from the solution until its concentration reaches a point where Henry's law is satisfied.

Transitions from solid to liquid (fusion), liquid to gas (vaporization), and solid to gas (sublimation) have

positive enthalpy values (they are endothermic).

osmotic pressure

pressure that must be applied to prevent osmotic movement across a selectively permeable membrane

colligative properties

properties that depend on the concentration of solute particles but not on their identity. i.e. Vapor pressure lowering Freezing-point depression Boiling point elevation Osmotic pressure

When the enthalpies of fusion, vaporization, and sublimation are given in joules per gram, the product of the enthalpy and the mass of the substance, m, gives the heat change in joules:

q=M(deltaH)

normal boiling point

s the boiling point of a liquid at a pressure of 1.00 atm. For example, when liquid water at 100°C and 1.00 atm is heated, it boils.

Raoult's law

states that the vapor pressure of a volatile component of a solution is equal to the mole fraction of the component times its vapor pressure when it is a pure liquid. That is, for volatile component Z, Pz=XzPz A solution that follows Raoult's law exactly is called an ideal solution. In an ideal solution, the intermolecular attractions between any two particles are equally strong, whether they are two solute particles, a solute and solvent particle, or two solvent particles. Since like dissolves like, the strengths of the intermolecular attractions between the particles in many solutions are close enough to ideal that many solutions follow Raoult's law approximately.

crystalline solid

such as an ice cube or a sodium chloride crystal, have definite melting points, while amorphous solids, such as a chocolate bar or glass, get softer as the temperature is raised and gradually form a liquid. The structures of crystalline solids feature regularly repeating arrangements of the constituent particles, whereas the structure of amorphous solids is not regular. Instead, it is less organized and more like the structure of particles in liquids.

Metallic solids

such as iron or mercury, are composed of metal ions loosely held together by their valence electrons, so they have a broad range of melting points. it takes a great deal of energy to disrupt ionic or covalent bonds, which explains why ionic and covalent-network solids have melting points in the hundreds or thousands of degrees Celsius. Much less energy is needed to disrupt intermolecular forces, so molecular solids have melting points below about 200°C.

ionic solids

such as sodium chloride, are composed of ions interacting via ionic bonds, so they have quite high melting points.

molecular solids

such as water or carbon dioxide, are molecules, so they interact via intermolecular forces and melt at relatively low temperatures.

capillary action

the ability of a liquid to flow against gravity up a narrow tube. Molecules of a liquid such as water can form intermolecular forces with the material on the inner surface of the tube, causing the water to move into the tube. Because the molecules of a liquid are interconnected via intermolecular forces, this loose network climbs up the tube as the lead molecules continue to form attractions to the inner surface of the tube. adhesion and cohesion help to explain this phenomena

boiling point elevation

the difference in temperature between the boiling point of a solution and the boiling point of the pure solvent

freezing point depression

the difference in temperature between the freezing point of a solution and the freezing point of the pure solvent

surface tension

the force that acts on the surface of a liquid and that tends to minimize the area of the surface. also determined by the strength of the intermolecular forces. Molecules in the center of a liquid sample can interact via intermolecular forces with other molecules of the liquid in all directions (Figure 12.12), resulting in no net pull in any direction for any molecule.

The concentration unit of percent by mass

the mass of the solute divided by the mass of the solution, times 100%.

van't Hoff factor

the ratio of moles of particles in solution to moles of solute dissolved

The enthalpy of solution depend

the strength of the intermolecular forces in the solute, the solvent, and the solution.

normal boiling point for liquid is....

the temp and at which vapor pressure equals 1 ATM or 760mmHG. Hvap is always positive.

The melting point of a solid substance depends largely on

the type of bond that is holding the particles of the solid together. The general order is molecular solids < metallic solids < ionic and covalent-network solids.

The terms saturated, unsaturated, and supersaturated do not apply

to mixtures of gases or to miscible liquids or solid solutions because there is no upper limit of solubility in these cases. Instead, the substance present in the greater amount is defined as the solvent, and the other is the solute.

The Clausius-Clapeyron equation relates the

vapor pressure of a substance at a specific temperature and its heat of vaporization.

volatile

vol

Molarity

which is the number of moles of solute per liter of solution

boiling point elevation equation

ΔTb=Kbm

freezing point depression equation

ΔTf = Kfm

Viscosity

A liquid's resistance to flowing.is determined by the strength of the intermolecular attractions and, to a lesser extent, the length of the molecule. Substances with strong intermolecular forces are more viscous than are substances with weaker intermolecular forces. Gasoline, a nonpolar substance with only dispersion forces, flows more readily than does water, a polar substance that forms hydrogen bonds. and determined by temprature increasing also increases kinetic energy and decreases the viscosity allowing it to flow more freeely.

isotonic solution

A solution in which the concentration of solutes is essentially equal to that of the cell which resides in the solution

hypertonic solution

A solution in which the concentration of solutes is greater than that of the cell that resides in the solution

hypotonic solution

A solution in which the concentration of solutes is less than that of the cell that resides in the solution

equillibrium

As liquid molecules escape into the gas phase in a closed system at constant temperature, the pressure of the vapor builds up and condensation will occur (Figure 12.24). As the vapor pressure increases, the rate of condensation increases. At some point, the rate of evaporation of liquid molecules will be equal to the rate of condensation of gas molecules, forming.

Henry's law.

At any given temperature, the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the surface of the liquid. This statement is known as. Concentration of dissolved gas in a solution=kP where k is the Henry's law constant, which depends on temperature and is different for each combination of gas and solvent, and P is the partial pressure (Section 11.7) of the gas above the liquid.

properties of a liquid

At least half of the particles in a liquid are touching in a liquid and are able to move over each other and form irregular arrangement. However liquids are able due to this to move a bit at random and are more energetic then solids. In order to fully break down the particles energy must be provided in some way for this to happen.giving liquids properties such as viscosity, surface tension, and capillary action.

Calculate the energy required to change a 17.0 g sample of liquid water from 87.7°C to steam at 121.0°C and 1.00 atm

Calculate each segment separately. Segment 1: The water in the liquid phase is heated from 87.7°C to its boiling point, 100°C. Segment 2: It then boils, producing water vapor at 100°C. Segment 3: The water vapor is then heated to 121.0°C. Since the amount of water is given in grams, use the "per gram" values of enthalpy and specific heat from Table 12.3. Segment 1: Heating the liquid water involves the use of the specific heat of liquid water and Equation 10.8. Segment 2: To vaporize the water, use the enthalpy of vaporization and Equation 12.1. Segment 3: For heating the water vapor, use the specific heat of gaseous water and Equation 10.8. The last step is to add the energy values together.

phase diagram

a graph showing the conditions at which a substance exists as a solid, liquid, or vapor

covalent-network solids,

also known as macromolecular solids. They consist of atoms connected by covalent bonds throughout the solid, so they have extremely high melting points.

Solution

any homogeneous mixture, and homogeneous mixtures can be made up of almost any two phases of matter mixed together. In solutions, one substance is dissolved in another, where the dissolved substance is known as the solute and the substance it is dissolved in is the solvent.