GAS LAWS – SOLUTIONS – ACIDS & BASES
KINETIC MOLECULAR THEORY (KMT) (pp. 426-429)
1. The kinetic molecular theory was developed to help predict the behavior of gases. It describes the behavior of gases at the molecular level.
2. This theory is based on assumptions about a theoretical gas known as an ______.
3. The assumptions are:
a. Ideal gas particles are so small that the volume of the individual particles if they were at rest is essentially zero when compared with the total volume of the gas.
b. Ideal gas particles are in constant, rapid, random motion, moving in straight lines in all directions until they collide with other particles.
c. There are no attractive or repulsive forces between particles and collisions between particles are elastic.
d. The average kinetic energy of the particles is directly proportional to the absolute temperature (measured in Kelvins).
FOUR VARIABLES DESCRIBE A GAS
Temperature
1. The temperature of a gas determines the average kinetic energy of the particles.
2. While the average kinetic energy of a collection of gases at a given temperature will be same, the velocity at which they travel will not. This is because the mass values of the various gases are different.
3. Temperature is usually measured in either Celsius or Kelvin. Both are related to one another:
Volume
1. Gas volumes are expressed four different ways:
Pressure
1. Pressure is a measure of the total force exerted by the moving particles of a gas as they collide with the walls of the container.
2. Atmospheric pressure is measured in terms of:
Standard Temperature and Pressure (STP)
1. In order to study the effects of changing temperature and pressure on a gas, one must have a standard for comparison.
2. STP represents a pressure and temperature that are fairly easy to reproduce:
Particles
1. Gases with equal volumes under the same conditions of pressure and temperature have equal numbers of particles.
2. This is ______and it holds true only for gases.
3. The amount of gas is measured in ______.
4. The volume of one mole of gas at STP is known as the ______.
GAS LAWS (pp. 403-415)
1. The gas laws are a series of mathematical relationships that relate the following variables:
Charles’ Law
1. Relates volume and temperature.
2. As the temperature decreases, the volume of a gas decreases. As temperature increases, the volume of a gas increases.
3. The volume of a gas at constant pressure is directly proportional to the absolute temperature.
4. Charles’ Law helped prove the existence of absolute zero.
5. Mathematically this is:
***** A sample of gas occupies 24.0m3 at 100.0K. Determine its volume at 400.0K.
***** Gas in a balloon occupies 2.50L at 300.0K. At what temperature will the balloon expand to 7.50L?
Boyle’s Law
1. The volume of a gas at constant temperature is inversely proportional to the pressure.
2. Like Charles’ Law, we can write:
***** The gas in a balloon has a volume of 4.00L at 100.0kPa. The balloon is released into the atmosphere and the gas in it expands to a volume of 8.00L. Determine the pressure on the balloon at the new volume.
***** If the pressure of a 2.50m3 sample of gas is 1.50 atm, what volume will the gas occupy if the pressure is changed to 7.50 atm?
Gay-Lussac’s Law
1. The pressure of a given gas varies with the Kelvin temperature when the volume remains constant.
2. This is expressed as:
***** The pressure of a gas in a tank is 324.24kPa at 295.0K. Determine the gas pressure if the temperature is raised to 333.0K.
***** A gas in a sealed container has a pressure of 125.0kPa at 30.00C. Determine the temperature in the container if the pressure is increased to 201.0kPa.
Dalton’s Law (pp. 420 – 425)
1. The total pressure in a gas mixture is the sum of the partial pressures of the individual components.
2. The ______of a gas is the pressure of an individual gas in a gas mixture that contributes to the total pressure of the mixture.
3. This is expressed mathematically as:
4. Dalton’s law is often used to determine the pressure of a gas collected over water.
***** Hydrogen gas is collected over water at a total pressure of 95.0kPa. The volume of gas collected is 28.0mL at 25.00C. Determine the partial pressure of the hydrogen gas if the water vapor pressure is 3.17kPa.
***** A gas is collected over water at 50.00C and a barometric pressure of 105.00kPa. Determine the pressure of the gas if the water vapor pressure is 12.34kPa.
COMBINED GAS LAW
1. The combined gas law states the relationship among pressure, volume and temperature of a fixed amount of gas:
2. The combined gas law allows one to work out problems involving more variables that change.
***** A gas at 110.0kPa and 30.00C fills a flexible container with an initial volume of 2.00L. If the temperature is raised to 80.00C and the pressure increased to 440.0kPa, what is the new volume?
***** At 0.000C and 1.00 atm pressure, a sample of gas occupies 30.0mL. If the temperature is increased to 30.00C and the entire gas sample is transferred to a 20.0mL container, what will be the gas pressure inside the container?
IDEAL GAS LAW (pp. 415-420)
1. The number of moles is the fourth variable that can be used along with pressure, volume and temperature to describe a gas.
2. The ideal gas law is:
3. If pressure is expressed in atmospheres, then:
4. If pressure is expressed in kPa, then:
***** Determine the number of moles of gas in a 3.00L container at 300.0K and a pressure of 1.50 atm.
***** Determine the Celsius temperature of 2.49 moles of gas contained in a 1.00L container at a pressure of 143kPa.
SOLUTIONS
WHAT ARE SOLUTIONS?
Characteristics of Solutions
1. Solutions are homogeneous mixtures containing two or more substances called the solute and the solvent.
2. The ______is the substance that dissolves.
3. The ______is the dissolving medium.
4. A solution may exist as a gas, liquid or solid depending on the state of its solvent.
5. Solutions can contain more than one solute.
6. Some combinations of substances can readily form solutions and others do not.
7. A substance that dissolves in a solvent is said to be ______in that solvent.
8. A substance that does not dissolve in a solvent is said to be ______in that solvent.
9. Two liquids that are not soluble in each other are said to be ______.
10. Two liquids that are soluble in each other are said to be ______.
Solvation in Aqueous Solutions
1. To form a solution, solute particles must separate from one another and the solute and solvent particles must mix.
2. Forces of attraction exist between the pure solute particles, between the pure solvent particles, and between the solute and solvent particles.
3. When a solid solute particle is placed in a solvent, the solvent particles completely surround the surface of the solid solute.
4. If the forces of attraction between the solvent and solvent particles are greater than the attractive forces holding the solute particles together, the solvent particles pull the solute particles apart and surround them.
5. These surrounded solute particles then move away from the solid solute out into the solution.
6. The process of surrounding solute particles with solvent particles to form a solution is called ______. When it occurs in water it is called ______.
7. ______is the general rule used to determine whether salvation will occur in a specific solvent.
8. Water will dissolve ionic compounds such as sodium chloride and polar compounds such as sucrose, but not nonpolar substances such as oil.
Factors That Affect Rate of Solvation
1. For salvation to occur the solute and solvent particles must come in contact with one another.
2. There are three ways to increase the collisions between solute and solvent particles which then increases the rate of solvation:
a.
b.
c.
Heat of Solution
1. Energy is needed to overcome the forces of attraction of the solute particles for each other and solvent particles for each other.
2. This process is ______.
3. When the solute and solvent particles mix, they are attracted to one another and energy is released. This process is ______.
4. The overall energy change that occurs during solution formation is called the ______.
Solubility
1. Only a limited amount of solute can dissolve in a solvent at a given set of conditions.
2. ______refers to the maximum amount of solute that will dissolve in a given amount of solvent at a specified temperature and pressure.
3. It is expressed in terms of:
4. When a solute dissolves, its particles mix in with the solvent particles. As time passes, the spaces available to the solute particles decrease and they collide with one another and the original crystal. Some of the solvated particles will re-attach themselves to the crystal.
5. As long as the rate of salvation remains greater than the rate of crystallization, salvation will continue.
6. Depending on the amount of solute present, the two rates may eventually equalize and no more solute appears to dissolve.
7. A state of dynamic equilibrium is reached. As one particle is solvated, another crystallizes. The overall amount of dissolved solute remains constant.
8. Such a solution is said to be a ______; it contains the maximum amount of dissolved solute for a given amount of solvent at a specific temperature and pressure.
9. An ______is one that contains less dissolved solute for a given temperature and pressure.
Factors That Affect Solubility
1. Pressure affects the solubility of gases. The greater the pressure, the more gas that can be dissolved in a liquid.
2. Solubility also depends on the nature of the solute and the solvent.
3. Temperature affects the solubility of all substances. For most substances, increasing the temperature of the solvent increases the solubility of the solute.
4. A ______can be formed using temperature effects. This type of solution contains more dissolved solute than a saturated solution at the same temperature.
5. Pressure affects the solubility of a gas. The solubility of a gas in any solvent increases as its external pressure increases.
Solubility Curves
1. Solubility curves can be used to predict the mass of a solute that will dissolve in 100g of water at various temperatures.
***** Using the solubility curves provided, answer the following questions:
a. Determine the solubility of potassium nitrate (KNO3) at 600C.
b. Determine which salt, ammonium chloride (NH4Cl) or potassium chloride (KCl) has a greater solubility at 00C.
c. Determine which of the following salt’s solubility in water is most temperature dependent: sodium nitrate (NaNO3), potassium chloride (KCl) or sodium chloride (NaCl).
***** A saturated solution of NaNO3 in 100g of water at 600C is cooled to 100C. Determine the mass, in grams, of solute that will precipitate out of solution.
***** A solution of NH4Cl in 100g of water at 600C contains 52.0g of solute. This solution is ______.
***** A solution of HCl in 100g of water at 400C contains 61.0g of solute. This solution is ______.
***** A solution of KClO3 in 100g of water at 800C contains 45.0g of solute. This solution is ______.
SOLUTION CONCENTRATION
1. The ______of a solution is a measure of how much solute is dissolved in a specific amount of solvent or solution.
2. Concentration may be described qualitatively as either ______or ______, but these are not useful to a chemist.
Molarity
1. ______is the number of moles of solute dissolved per liter of solution.
2. ______is read as ______.
3. To calculate a solution’s molarity, one must know the volume of the solution and the amount of dissolved solute:
***** Determine the molarity of an aqueous solution containing 40.0g of glucose (C6H12O6) in 450.0 mL of solution.
***** A bleach solution of NaOCl has a concentration of 0.128M. Determine the mass of NaOCl in the solution if its volume is 1.00 L.
Preparing Molar Solutions
1. Many lab solutions are prepared by diluting stock solutions purchased from a supply company.
2. To determine the volume of stock solution that must be diluted use:
***** Determine the volume, in mL, of a 3.00M KI stock solution needed to make 0.300 L of a 1.25M KI solution.
***** Determine the molarity of a dilute solution made by starting with 20.0 mL of a 3.50M stock solution and diluting it to 100.0 mL.
COLLIGATIVE PROPERTIES OF SOLUTIONS
1. Solutes affect some of the physical properties of their solvents.
2. Most of these effects are caused by the number of particles in the solution rather than the type of particle in solution.
3. Physical properties of solutions that are affected by the number of particles, but not the identity of dissolved solute particles are called ______.
4. Colligative properties include:
Electrolytes and Colligative Properties
1. Ionic compounds are called electrolytes because they dissociate in water to form a solution that conducts an electric current.
2. Some molecular compounds also ionize in water.
3. Electrolytes that produce many ions are called strong electrolytes while those that produce only a few ions in solution are called weak electrolytes.
4. Compare the dissolution of 1 mole of NaCl and 1 mole of CaCl2 in water:
Vapor Pressure Lowering
1. Vapor pressure is he pressure exerted in a closed container by liquid particles that have escaped the liquid’s surface and entered the gaseous state.
2. Adding a nonvolatile solute (one that has little tendency to become a gas) to a solvent lowers the solvent’s vapor pressure.
3. This is because the solvent’s surface is now a combination of solvent particles and solute particles. There are fewer solvent particles available to escape from the surface so fewer particles enter the gaseous state and the vapor pressure is lowered.
4. Thus, ______is due to the number of solute particles in solution.