Chem test
Chem-272
Unit 3
Chemical Bonding & Gas Laws
Topics
3.1 Ionic Bonding
3.2 Covalent Bonding
3.3 Molecular Geometry
3.4 Polarity & Intermolecular Forces
3.5 Gas Laws
Key Terms
electron dot notation
chemical bond
ionic bond
covalent bond
metallic bond
network solid
single bond
double bond
triple bond
lone pair
bond axis
bond angle
octet rule
VSEPR Theory
molecular geometry
central atom
terminal atom
tetrahedral
pyramidal
bent angular bent
trigonal planar
linear
electronegativity
polar bond
non-polar bond
polar molecule
non-polar molecule
miscible
immiscible
intramolecular force
intermolecular force
Supplementary Questions
3.1 Ionic Bonding
1. What does an electron dot diagram show? the number of valence electrons
2. What is the role of valence electrons in the formation of bonds?
3. DRAW electron dot diagrams for the following:
a. Ca b. Br c. O2- d. Ga3+
4. What is an ionic bond? When a nonmetal and metal bond
5. How may a neutral atom become an ion with a charge of 2+?
6. What 2 types of elements typically form an ionic bond?
7. Which of the following are formed by ionic bonds?
a. MgCl2 b. H2O c. CO2 d. K3N
8. Name three properties of ionic compounds.
3.2 Covalent Bonding
9. What is a covalent bond? When two non-metals bond together that share electrons to obey the octet rule
10. What types of elements typically form covalent bonds? non-metals
11. Why do the atoms of a noble gas not combine to form molecules? because it only consists of non-metals
12. Which of the following are formed by covalent bonds?
a. MgCl2 b. H2O c. CO2 d. K3N
13. Name three properties of covalent compounds. low melting/boiling points due to weak intermolecular forces, poor electrical conductivity (as they are generally neutral molecules), and high directional specificity
3.3 Molecular Geometry and Structures
14. What is the minimum number of atoms that must be present in a molecule to form a bond angle? 2
15. What does the VSEPR stand for? Valence shell electron pair repulsion
16. How many shared pairs does a trigonal planar structure have? 3
17. Why does water form a bent structure? When electrons repel eachother the angle decreases.
3.4 Polarity & Intermolecular Forces
18. What does electronegativity have to do with bond polarity? because the higher the elctronegativity, the more they will repel eachother depicting the non-polar or polar bond.
19. When is a covalent bond considered to be polar?
20. How is it possible for a molecule to be nonpolar when its individual bonds are polar?
21. For the following molecules, DRAW their lewis structures, identify the molecular geometry, bonding:nonbonding ratio, bond angle, and polarity.
PI3
CO
CH4
CCl2F2
22. Design a molecule with the listed properties. Give both a formula and Lewis structure of the molecule:
i. Must have only ONE central atom.
ii. The molecule CANNOT have an odd number of electrons and CANNOT be an ion.
iii. The molecule must have 2 bonding domains.
iv. The molecule must be polar.
v. The exterior atom(s) must be halogens.
3.5 Gas Laws
23. How does gas exert pressure? When they collide with eachother, and give out the pressure.
24. How does changing the temperature affect the volume in a balloon? The higher the temperature, the higher the pressure.
25. If there is no temperature change, how can you increase the pressure in a balloon?
26. Why is it important to check tire pressure in the winter? Because it varies by season, the lower temp the lower pressure and vice versa.
27. What is the difference between Boyle’s Law, Charles’ Law, and Gay-Lussac’s Law? Discuss the changes in pressure, temperature, and volume.
28. A sample of gas has a volume of 500 mL at a pressure of 640 torr. What volume will the
gas occupy at the same temperature but at the standard atmospheric pressure of 760
Torr?
29. A 4.2 L sample of gas at 1.0 atm and 25°C is heated to 85°C. Calculate the gas volume
in liters at the higher temperature if the pressure remains constant.
30. 10.0 L of a gas is found to exert 97.0 kPa at 25.0°C. What would be the required
temperature (in Celsius) to change the pressure to standard pressure?
3.1 Ionic Bonding
An ionic bond occurs when one atom donates an electron to another atom, resulting in positively and negatively charged ions. This exchange of electrons typically happens between metals, which lose electrons, and nonmetals, which gain electrons. The strong electrostatic attraction between these oppositely charged ions results in the formation of ionic compounds.
Properties of Ionic Compounds:
- High melting and boiling points due to strong ionic bonds.
- Generally soluble in water and form electrolytes when dissolved.
- Conduct electricity in molten and aqueous states.
3.2 Covalent Bonding
Covalent bonding involves the sharing of electrons between two nonmetal atoms. This sharing allows each atom to achieve full outer electron shells, adhering to the octet rule. Covalent bonds can be single, double, or triple bonds, depending on the number of shared electron pairs.
Properties of Covalent Compounds:
- Lower melting and boiling points compared to ionic compounds due to weaker intermolecular forces.
- Poor electrical conductivity as most covalent compounds do not form ions.
- Many are volatile or gases at room temperature.
3.5 Gas Laws
Gas laws describe the behavior of gases in relation to pressure, temperature, and volume. Understanding these laws is crucial for predicting how gases respond to changes in their environment.
Boyle’s Law: At constant temperature, the pressure of a gas is inversely proportional to its volume. Mathematically expressed as:
Charles’ Law:
At constant pressure, the volume of a gas is directly proportional to its absolute temperature. Given as:Gay-Lussac’s Law:
At constant volume, the pressure of a gas is directly proportional to its absolute temperature:
These laws can help explain how and why gases expand, contract, and react under different conditions, allowing for calculations in chemistry and engineering.