Trends in Periodic Table
What is being described?
Across a period: Generally increases due to increasing nuclear charge.
Down a group: Generally decreases due to increasing atomic size.
Ionization energy / Electronegativity
These are the substances that are formed as a result of a chemical reaction. They are present at the end of the reaction and are produced from the reactants.
Products
How many particles are present in one mole of a substance?
6.022 x 1023 particles
What type of intermolecular force occurs between these polar molecules?
Hydrogen Chloride (HCl)
Dipole - Dipole Interaction
Analogy
adhesion < cohesion : _______ meniscus
adhesion > cohesion : _______ meniscus
Answer:
convex meniscus : concave meniscus
What is being described?
Across a period: Generally decreases due to increasing nuclear charge pulling the electrons closer.
Down a group: Generally increases due to the addition of energy levels.
Atomic Radius
What do you call the numbers written in front of chemical formulas in a balanced chemical equation?
HINT : They represent the relative amounts of reactants and products involved in the reaction.
Coefficients
What is the difference between a formula unit and a molecule in terms of the mole concept?
Formula unit refers to the simplest ratio of ions in an ionic compound
Molecule refers to a group of atoms bonded together covalently
Which type of intermolecular force is primarily responsible for the attraction between sodium ions (Na+) and chloride ions (Cl-) in solid sodium chloride (NaCl)?
Answer:
Ion-Ion Forces of Attraction
Which of the following substances would be the most soluble in water?
a. CH3CH2NH2 b. CH3CH2CH2CH2NH2
c. CH3CH2CH2Br d. CH3CH2CH2CH3
Answer:
a. CH3CH2NH2
Which group on the periodic table contains elements with the highest electronegativity?
Group 17 - The halogens
This law states that the total mass of substances does not change during a chemical reaction.
Law of Conservation of Mass
Problem:
Calculate the mass of 3 moles of carbon dioxide (CO2).
Answer:
132.03 grams of CO2
Which of the following substances has the highest strength of hydrogen bonding?
a. Water (H2O)
b. Ammonia (NH3)
c. Hydrogen fluoride (HF)
d. Hydrogen sulfide (H2S)
Answer:
c. Hydrogen Fluoride (HF)
This large electronegativity difference results in a strong dipole moment, with the hydrogen atom carrying a partial positive charge and the fluorine atom carrying a partial negative charge.
Vaporization occurs more readily with ______.
(Give at least two factors)
Answer:
1. Increased temperature
2. increased surface area of the liquid
3. decreased intermolecular forces of attraction
Which of the following elements is the most electronegative?
A. Titanium B. Gallium
C. Phosphorus D. Barium
C. Phosphorus
Balance this chemical equation:
Na + Cl2 = NaCl
Balanced chemical equation:
2Na + Cl2 = 2NaCl
Problem:
Convert 5.0 x 1024 atoms of oxygen (O) to moles.
Answer:
8.30 moles of Oxygen
Which of the following substances exhibits London dispersion forces as its primary intermolecular force?
a. Methane (CH4) b. Water (H2O)
c. Hydrogen chloride (HCl) d. Neon (Ne)
Answer:
a. Methane (CH4)
Methane (CH4) exhibits London dispersion forces as its primary intermolecular force because it is a nonpolar molecule.
For liquids, viscosity decreases with increasing temperature.
For gases, the viscosity increases with increasing temperature.
Describe their relationship.
Answer:
Liquids : inverse relationship.
Solids : direct relationship.
Why does the electronegativity increase across a period?
Increase in effective nuclear charge
Decrease in atomic radius
Balance this chemical equation:
C3H8 + O2 = CO2 + H2O
C3H8 + 5O2 = 3CO2 + 4H2O
Problem:
A scientist has 10 grams of water (H2O). How many molecules of oxygen (O) does the scientist have?
Answer:
≈ 3.34 x 1023 molecules of Oxygen
How does temperature relate to the kinetic energy of gas particles according to the kinetic molecular theory?
Temperature is directly proportional to the average kinetic energy of gas particles.
As temperature increases, the average kinetic energy of gas particles also increases.
Liquids with stronger intermolecular forces have more tendency to escape into gas.
True or False? Explain.
FALSE.
Liquids with stronger intermolecular forces have higher cohesive forces, which means they are more tightly held together in the liquid phase. As a result, these molecules have a lower tendency to escape into the gas phase compared to molecules with weaker intermolecular forces.