In this week we will
1 Revise the material needed for HW and AMS Sunday For previous week 9
Last week Ch.6: 6.2.1 – 6.2.3 6.3.3 – 6.3.6, 6.3.9
2 Study the material needed to go through week 10 material
Continue Studying for Chapter 6
AMS MATERIAL
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What is meant by ideal gas?
An ideal gas is a gas that does not liquefy
The molecules of an ideal gas have negligible volume
The molecules of an ideal gas exert no forces of attraction between them
Open end Manometer
- measure the difference between the pressure of a gas in a container and the atmosphere. The pressure of the gas in the container is measured by the difference in height of mercury between the two arms of the manometer.
- If the level of the mercury in the open-end side is higher than the level on side in contact with the gas, then the pressure of the gas is more than atmospheric by the difference of the levels.
- If the gas pressure in the container is equal to atmospheric pressure, the level of mercury on both sides of the tube is the same
Changing Celsius To Kelvin Temperature measurement and vice versa
Change 373 K to °C. T = t°C + 273 ,
Change 27°C to Kelvin. T = t°C + 273
Relationship of molar volume with atomicity
molar volume tends to decrease with increasing atomicity
Temperature and Pressure relationship
According to the kinetic theory, at a higher temperature a gas exerts a higher pressure because
its particles collide with the walls of the container more frequently
its particles collide with the walls of the container more strongly
move more rapidly
Average kinetic energy and temperature relationship
According to the kinetic theory, the molecules of the oxygen gas have, at the same temperature the same average kinetic energy as hydrogen molecules
Absolute zero temperature
pressure exerted by any gas become zero
T = 0 (as the pressure of an ideal gas is directly proportional to the absolute temperature)
when the volume of the gas becomes practically zero
at -273.16°C
magnitude of kelvin and Celsius
The size of the kelvin is the same size as the Celsius degree: 1K = 1°C.
Relationship between molar mass and FP BP
the higher the molar mass the higher is the FP and BP.
Definition of partial pressure
The partial pressure of a gas in a mixture of gases placed in a vessel is The pressure a gas would exert if it were alone in the vessel.
Relationship between molar volume and molar mass
the molar volume tends to decrease with increasing molar mass
Behavior of real gases
real gases liquefy at high pressures and low temperatures
only approximately obey P×V = const.
Equation state of ideal gas
PV = nRT
The barometer
The barometer is used to measure the atmospheric pressure.
The atmosphere unit definition
The atmosphere is the pressure that
can support a column of mercury 760 mm high at 0°C
can support a column of mercury 76 cm high at 0°C.
Volume of one more of gas
What is the volume of one mole of gas at STP 22.4 dm³
Chemical formula
- In the case of molecular compounds it is also known as the molecular formula.
- It gives the number and the kind of atoms of each element in a molecule of that compound.
- It can be used to obtain the simplest ratio of atoms in the molecular compound.
A simplest formula
In the case of molecular compounds it gives the simplest ratio in which the atoms are found
together.
In the case of salt it gives the simplest ratio in which the ions are found together.
CLH18-WRCC
pure substance?
a) carbon dioxide gas
b) ammonia gas
c) sea water
d) copper sulfate crystals
e) copper sulfate solution
f) solid iron
g) Air
h) nitrogen gas
i) liquid mercury
Statements describing a liquid
a) The particles of a substance are the far apart from each other.
b) The free space between the particles allows the sample to change its volume.
c) The particles move with respect to each other which causes changes in the shape of the sample.
d) The limited space between the particles does not allow the sample to be compressed.
Define a mole of particles
How many moles are present in 8.0 g of oxygen gas, O2
How many moles are there in 3.0 × 1023 molecules of H2S??
What is the mass of 2.0 mol of CH4, in grams?
How many molecules are contained in a sample of 1120 cm3 of methane, CH4, at STP?
Find the number of molecules of carbon dioxide CO2 present in 0.360 dm3 at RTP.
Given: Molar volume at RTP = 24.0 dm3, NA = 6.00×1023
A compound has a molar mass of 78.0 g/mol. If its simplest formula is CH, find its molecular formula.
Given the equation: 4NH3 + 7O2 → 6H2O + 4NO2
What is the mass reacting ratios for the above equation? [N = 14; O = 16; H = 1]
In the balanced equation below, at STP, write the reacting ratio by volume of reactants and products.
2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O(l)
0.10 mole of oxygen gas and 0.40 mole of nitrogen gas are placed in an empty container of volume 20
liters. The total pressure in the container is 0.50 atm. Find the volume of the oxygen gas.
A 6.0 dm3 flask is filled with dry air to 1,000 mmHg pressure. Air is 20 percent O2 and 80 percent N2 by
volume (this means by mole ratio). What is the partial pressure of each gas?
Balance the equations.
a) Na + Cl2 → NaCl
b) Na + O2 → Na2O2
c) Al + Cl2→AlCl3
d) P4 + O2→ P4O6
e) NH3 → H2 + N2
f) NH3 + O2 → H2O + NO2
g) C5H12 + O2 → H2O + CO2
h) C2H5OH + O2 → H2O + CO2
http://www.kanayatichemistry.com/courses/sabis-chemistry-grade-10-level-l-full
pure substance?
a) carbon dioxide gas
b) ammonia gas
c) sea water
d) copper sulfate crystals
e) copper sulfate solution
f) solid iron
g) Air
h) nitrogen gas
i) liquid mercury
Statements describing a liquid
a) The particles of a substance are the far apart from each other.
b) The free space between the particles allows the sample to change its volume.
c) The particles move with respect to each other which causes changes in the shape of the sample.
d) The limited space between the particles does not allow the sample to be compressed.
Define a mole of particles
How many moles are present in 8.0 g of oxygen gas, O2
How many moles are there in 3.0 × 1023 molecules of H2S??
What is the mass of 2.0 mol of CH4, in grams?
How many molecules are contained in a sample of 1120 cm3 of methane, CH4, at STP?
Find the number of molecules of carbon dioxide CO2 present in 0.360 dm3 at RTP.
Given: Molar volume at RTP = 24.0 dm3, NA = 6.00×1023
A compound has a molar mass of 78.0 g/mol. If its simplest formula is CH, find its molecular formula.
Given the equation: 4NH3 + 7O2 → 6H2O + 4NO2
What is the mass reacting ratios for the above equation? [N = 14; O = 16; H = 1]
In the balanced equation below, at STP, write the reacting ratio by volume of reactants and products.
2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O(l)
0.10 mole of oxygen gas and 0.40 mole of nitrogen gas are placed in an empty container of volume 20
liters. The total pressure in the container is 0.50 atm. Find the volume of the oxygen gas.
A 6.0 dm3 flask is filled with dry air to 1,000 mmHg pressure. Air is 20 percent O2 and 80 percent N2 by
volume (this means by mole ratio). What is the partial pressure of each gas?
Balance the equations.
a) Na + Cl2 → NaCl
b) Na + O2 → Na2O2
c) Al + Cl2→AlCl3
d) P4 + O2→ P4O6
e) NH3 → H2 + N2
f) NH3 + O2 → H2O + NO2
g) C5H12 + O2 → H2O + CO2
h) C2H5OH + O2 → H2O + CO2
Condensed phases of matter are solid and liquid
Gaseous elements (under room conditions) are found at the top right hand side of the
Periodic Table.
Examples of element that are found as gases are:
Hydrogen, H2 Helium, He Radon, Rn
Nitrogen, N2 Neon, Ne
Oxygen, O2 Argon, Ar
Fluorine, F2 Krypton, Kr
Chlorine, Cl2 Xenon, Xe
One gram of steam, H2O (g) causes more severe burns than one gram of water, H2O(l) at
100oC. At the same temperature, both have the same average kinetic energy but steam has a higher potential energy than water.
A volatile liquid is a liquid that evaporates at room temperature. A liquid with a low
boiling point is easy to vaporize.
Vapor pressure of a liquid: is the pressure of the gas above the liquid with which it is at
equilibrium (Both liquid and gas exist indefinitely).
Vapor pressure of a liquid in a sealed container depends on temperature of the flask. As
the temperature increases the vapor pressure of a liquid increases.
At the boiling point, the temperature of a pure substance stays constant as the liquid is
being heated until all the liquid changes into gas. The heat given to the liquid causes more liquid to change into gas.
Molar heat of vaporization is the minimum energy required to change one mole of a
substance from liquid to gas at the same temperature.
General equation for Molar heat of vaporization: X (l) + heat ⇌ X (g)
General equation for Molar heat of condensation: X (g) ⇌ X (l) + heat
In general, a substance that has a higher boiling point is expected to have a higher molar
heat of vaporization.
NOTES:
1. Vapor pressure and temperature are proportional NOT directly proportional.
2. At the same temperature, the vapor pressure is the SAME.
3. For the same liquid, the only factor affecting the pressure of the liquid is the
temperature.
Minimum conditions for liquid molecules to vaporize:
1) Molecules are supposed to be on the surface.
2) Molecules are supposed to have an average kinetic energy greater than the energy
keeping the molecules in the liquid state.
Boiling point: is the temperature at which the liquid vaporizes anywhere in the solution.
At the boiling point:
a. Vapor pressure is equal to the surrounding pressure.
b. Bubbles of vapor can form anywhere within the liquid.
c. Molecules escape from the surface of the liquid to enter the gas phase as vapor (this also
happens at room temperature).
d. With increasing altitude, atmospheric pressure decreases and so does boiling point.
Normal boiling point: is the temperature at which the vapor pressure is exactly 1 atm or
760 mmHg.
Molar heat of fusion: is the energy required to change one mole of a substance from
solid to liquid at the same temperature and constant pressure.
X (s) + heat ⇌ X (l)
Molar heat of fusion is less than the molar heat of vaporization. Molar heat of
vaporization of water is 7 times molar heat of fusion of water.
In general, a pure substance that has a high melting point is expected to have a high molar heat of fusion.
Comparison between the energy of the molecules on the three states of matter.
Highest PE in gases and lowest PE in solids. The PE of liquid is less than in gases and more
than in solids.
Average KE is the same in all the states of matter at the same temperature.
During melting, the energy absorbed is stored as PE. This stored energy is used to change
state form solid to liquid and not to raise the temperature. Therefore, the temperature stays constant.
Heating curve:
As temperature increases: KE increases, PE stays the same
At constant temperature: KE stays the same, PE increases.
The average kinetic energy is directly proportional to absolute temperature. At constant
temperature, average kinetic energy remains the same.
212. If a molecule on the surface of a liquid is given a sufficient push from below, it may be able to escape and join the gaseous state.
213. The molecule that leaves the surface jumps out with a lot of kinetic energy, energy that is stored as potential energy.
214. The average kinetic energy of the remaining molecules decreases. The liquid cools down.
When a liquid evaporates its vapor pressure starts to rise. Eventually, molecules come
back and join the liquid at the same rate they are escaping it. The net amount of liquid molecules and gaseous molecules becomes constant. No more cooling takes place because the rate at which molecules leave and cool the liquid is equal to the rate at which the molecules come back and heat the liquid. Equilibrium is reached. It is this “maximum” or “equilibrium” pressure that is called the vapor pressure of the liquid at the given temperature
When we sweat on very humid days our bodies do not cool down
The vapor pressure increases with increasing temperature.
When the vapor pressure equals the atmospheric pressure, the liquid boils.
Sometime a liquid is heated to a temperature above its boiling point and it does not boil.
The liquid is said to be superheated. This is dangerous because any small agitation will cause the liquid to evaporate explosively spraying all with very hot liquid.
To prevent superheating in the laboratory, we add a few boiling chips to a liquid before
boiling it.
Source course revision questions
Chapter 1 Laboratory Skills
Section 1.2 Chemical Apparatus
Basic Questions
1. What is the use of each of the following pieces of apparatus?
a) Measuring cylinder
b) Beaker
c) Separating funnel
d) Test tube holder
e) Wire Gauze
2. What are the rules that should be followed when using a Bunsen burner?
3. What are the rules that should be followed when heating a test tube?
4. How do you read the volume of a liquid in a measuring cylinder? How many
readings of the cylinder must you make to determine the volume of the liquid in
it?
5. a) What is meant by each of the following terms: filter paper, filtrate, and residue?
b) How would you separate the sand from a mixture of sand and seawater?
6. Explain the steps involved in filling a pipette.
7. How many drops is 1.0 mL of liquid?
8. Explain the steps involved in filling a burette.
Grid Questions
^
1. Name the most suitable glassware to:
a) prepare a solution with a specific volume most accurately.
b) measure a specific volume of a liquid to the nearest 0.05 mL.
c) measure variable volumes of a liquid to the nearest 0.1 mL.
d) to mix liquids in it.
2. You are required to obtain some salt crystals from a salt solution. List in the
correct order the series of steps that have to be followed.
3. a) Which of the diagrams below represent the setup used for filtration?
b) Name the apparatus required to perform a filtration.
4. Name the most suitable technique to separate:
a) a soluble salt from an aqueous solution.
b) an insoluble solid from a mixture.
