CHEM 111 Lecture Notes - Lecture 1: 100 Metres, Vaporization, Distillation

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bronzellama300

15 Dec 2016

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All things that are physically real -- from the air we breathe to the ground we walk on -- are forms of matter. Matter is everything in the universe that has mass and occupies space. Chemistry is the study of the composition, structure and properties of matter. A solid has a definite volume and shape. A liquid has a definite volume but not a definite shape. A gas (or vapor) has neither a definite volume nor a definite shape. Or they may be groups of atoms called. Rather, it expands to occupy the entire volume and shape of its container. Instead, it takes the shape of the container it is in. molecules that are held together in a characteristic pattern and proportion by forces called chemical bonds. A tray of ice cubes stored in a frost-free freezer slowly disappears as solid ice becomes water vapor in a process called sublimation.

Related Questions

Dry ice is simply frozen carbon dioxide (carbon dioxide in the solid state) and is pretty cold with a temperature of -109.3 degrees F (-78.5 degrees C). For comparison, liquid nitrogen is MUCH colder at -321 degrees Fahrenheit (-196 degrees Celsius).The carbon dioxide in dry ice will also go directly from the solid state (frozen carbon dioxide) to the gaseous state. This process is called sublimation.

You have likely seen examples of sublimation in your own freezers on food items, such as meat, that are kept for long times in the freezer, and/or not well sealed from the air. This is often called âfreezer burnâ, and it is caused by the sublimation of water molecules from ice crystals present on the surface of meat into the dry freezer air.

You have 2.44 grams of dry ice in a 6.0 Liter container maintained at 31.2⁰C. What is the pressure in the container after ALL the dry ice has sublimated (transformed to the gaseous state)?

-You will use the Ideal Gas Law here, and you must determine which specific value to use for the constant âRâ

* Circle the intermolecular force(s) that is/are present in each of the following species. [Hint: there may be more than one correct answer.]

Ar (hydrogen bonding, dipole-dipole forces, dispersion forces)

CH4 (hydrogen bonding, dipole-dipole forces, dispersion forces)

HBr (hydrogen bonding, dipole-dipole forces, dispersion forces)

HF (hydrogen bonding, dipole-dipole forces, dispersion forces)

CHCl3 (hydrogen bonding, dipole-dipole forces, dispersion forces)

* For the following pairs of atoms/molecules, circle the species that has the higher boiling point.

Ne or Xe

Cl2 or F2

HBr or HF

HCl or HI

H2O or H2S

* Phase changes always associate with change of enthalpy. For the following situations, name the phase

transition and indicate whether the process is exothermic or endothermic.

(a) Dry ice (solid carbon dioxide) turns to gaseous carbon dioxide.

Answer:

(b) Water vapor turns to liquid water.

Answer:

(d) Iodine vapor turns to solid iodine.

Answer:

(e) Liquid helium turns to helium gas.

Answer:

* True or false

1. Intermolecular forces are stronger than ionic and covalent bonds. Answer:

2. For molecules with similar size and molar mass, those with higher polarity would have higher boiling

point. Answer:

3. Ion-dipole forces exist between ionic potassium bromide and polar water.

Answer:

4. Dispersion forces exist between argon and helium. Answer:

5. Instantaneous dipoles exist in all molecules and atoms. Answer:

6. The strength of dispersion forces depends on the molar mass but the shape of the molecules have no effect on dispersion forces. Answer:

7. Ice has a higher density than water because ice has an ordered cagelike structure. Answer:

8. Liquids with weaker intermolecular interactions have lower viscosity. Answer:

9. Viscosity decreases with increasing temperature. Answer:

10. For any molecules, the heat of vaporization is always lower than the heat of fusion because it takes more energy to make molecules to move past one another in a solid lattice. Answer:

1. Which characteristic below describes ONLY a solid (not liquid or gas)?
a) definite shape b) particles in contact c) definite volume d) completely fills container
2. When iron rusts, it forms a reddish-brown solid. This is:
a) a physical change b) a chemical change c) no change at all
3. What is the name of FeSO4?
a) iron (I) sulfate b) iron (II) sulfate c) iron sulfite d) iron sulfide
4. A bottle label states that the bottle contains âdrinking water with minerals added for flavor. This would be an example of:
a) an element b) a compound c) a heterogeneous mixture d) a homogeneous mixture
5. Which answer has the correct number of significant figures for: length = 2.0 m + 0.2100 m?
a) 2.2 b) 2.21 c) 2.210 d) 2.2100
Place the answer with the correct number of significant figures on the lines provided below.
6. To drive one kilometer, how many centimeters should you drive?
_______________cm
7. A 10.0 gram block of gold has a density of 19.32 g/cm3. What is its volume?
______________cm3
8. What is the formula of sodium sulfide?
_________________________
9. What is the name of H2S?
_______________mm
10. How many neutrons are in 35Cl?
_______________ neutrons
For problems 11 through 13, show your work to receive full credit and use the correct number of significant figures in your final answer.
11. The density of nickel is 8.91 g/cm3. Calculate the mass of a nickel ball with a radius of 0.50 mm in grams.
(Ï = 3.1416; Vsphere = 4Ïr3/3)
12. The recommended adult dose of Elixophyllin , a drug used to treat asthma, is 6.00 mg/kg of body mass. Calculate the dose in milligrams for a 134-lb person.
13. It is 273 K outside. Do you need a jacket? Why or why not? (show your work for full credit)
14) Element X has three naturally occurring isotopes. The masses (amu) and % abundances of the isotopes are given in the table below. What is the average atomic mass of the element in amu?

isotope38 abundance of 5.07,mass of 37.919

isotope39x,abundance of 15.35,mass of 39.017

isotope 42,abundance of 79.85,mass of 42.111

15. Classify each of the following elements as alkali, alkaline earth, halogen or a noble gas:
a) He ________________________
b) F ________________________
c) Na ________________________
d) Ca ________________________
e) Br ________________________

CHEM 111 Lecture Notes - Lecture 1: 100 Metres, Vaporization, Distillation

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