Gases
What does Boyle's Law state about the relationship between pressure and volume of a gas at constant temperature?
Pressure and volume are inversely proportional (P₁V = P₂V2). If pressure increases, volume decreases.
What is the main difference between a homogeneous mixture and a heterogeneous mixture?
A homogeneous
mixture has a uniform composition throughout (like salt water), while a heterogeneous mixture has visibly different substances or phases (like sand in water).
What is the difference between an exothermic process and an endothermic process in terms of heat flow?
An exothermic
process releases heat into its surroundings (feels hot), while an endothermic process absorbs heat from its surroundings (feels cold).
According to the Collision Theory, what two key requirements must a collision between reactant molecules meet for a reaction to actually occur?
The reactant molecules must collide with the correct orientation and with sufficient energy (equal to or greater than the activation energy).
According to the Bronsted-Lowry definition, what is an acid and what is a base?
An acid is a proton donor, and a base is a proton acceptor.
According to Charles' Law, what happens to the volume of a gas if its absolute temperature is doubled while pressure is kept constant?
The volume will also double, because volume and temperature are directly proportional (V/T₁ = V₂/T2).
What is the molarity of a solution made by dissolving 0.5 moles of NaCI in enough water to make 2.0 liters of solution?
0.25 M (Molarity equals moles of solute divided by liters of solution, so 0.5 moles divided by 2.0 liters equals 0.25 M).
State the Law of Conservation of Energy
Energy cannot be created or destroyed in a chemical reaction or physical process; it can only be converted from one form to another.
What is activation energy?
The minimum amount of energy required to initiate a chemical reaction by transforming reactants into an activated complex.
What are the typical products of a neutralization reaction between a strong Arrhenius acid and a strong Arrhenius base?
Water and a salt (an ionic compound).
What is the volume occupied by 2.0 moles of an ideal gas at Standard Temperature and Pressure (STP)?
44.8 liters (Since 1 mole = 22.4 liters at STP, 2.0 moles times 22.4 liters equals 44.8 liters).
If you have 100 mL of a 6.0 M HCI stock solution, how much water must you add to dilute it to a concentration of 1.5 M
You need to add 300 mL of water. To dilute the concentration to one-fourth of its original strength, the total volume must become four times larger (400 mL). The added water is 400 mL minus the original 100 mL, which equals 300 mL.
How much heat energy (in Joules) is required to raise the temperature of 50 grams of water by 10 degrees Celsius? (The specific heat of water is 4.18 J/gC).
2090 Joules. Heat equals mass times specific heat times the change in temperature (50 grams times 4.18 times 10 degrees equals 2090 Joules)
Name three distinct factors that can be adjusted to increase the rate of a chemical reaction.
Increasing the temperature, increasing the concentration of reactants, increasing the surface area (by crushing a solid), or adding a catalyst.
What is the pH of a solution that has a hydrogen ion concentration of 1.0 x 10^-4 M, and is it acidic, basic, or neutral?
The pH is 4, and the solution is acidic (since pH is less than 7).
A gas sample has a volume of 3.0 liters at a pressure of 1.0 atm and a temperature of 300 K. If the volume is decreased to 1.5 liters and the temperature is increased to 600 K, what is the new pressure?
4.0 atm. Based on the combined gas law, reducing the volume by half doubles the pressure to 2.0 atm, and doubling the temperature doubles the pressure again, resulting in 4.0 atm.
Calculate the percent by mass of a solution created by dissolving 25 grams of sugar into 100 grams of water.
20 percent. Percent by mass equals mass of solute divided by total mass of solution times 100. So 25 grams divided by 125 total grams equals 0.2, which is 20 percent.
Look at a typical heating curve of water starting from ice to steam. Why does the temperature remain constant at O degrees Celsius and 100 degrees Celsius even though heat is continuously being added?
At those plateaus, a phase change is occurring (melting at 0 degrees and boiling at 100 degrees). The added heat energy is being used to break or weaken the intermolecular forces holding the molecules together in that phase, rather than increasing the kinetic energy (temperature) of the
molecules
How does adding a catalyst speed up a chemical reaction? Describe its effect on a reaction energy diagram.
A catalyst speeds up a reaction by providing an alternative reaction pathway with a lower activation energy. On a diagram, it lowers the peak of the curve representing the transition state, but leaves the energy of reactants and products unchanged.
Identify the conjugate acid-base pairs in the following chemical equation: NH3 + H2O <-> NH4+ + OH-
NH3 (base) and NH4+ (conjugate acid). Pair 2: H2O (acid) and OH- (conjugate base).
Explain how Gay-Lussac's Law applies to a rigid, sealed container (like a pressure cooker or aerosol can) when it is heated, and why this can be dangerous.
Gay-Lussac's Law states that pressure and absolute temperature are directly proportional at constant volume. In a rigid container, the volume cannot expand; as temperature increases, the kinetic energy of the gas molecules increases, causing more frequent and forceful collisions with the walls. This rapidly raises the internal pressure, which can exceed the container's strength and cause an explosion
Using the concept of intermolecular forces, explain the chemical reason behind the phrase "like dissolves like" when describing why oil will not dissolve in water.
Water is a highly polar molecule that forms strong hydrogen bonds with other water molecules. Oil consists of nonpolar hydrocarbon chains held together by weak dispersion forces. Oil cannot dissolve in water because the weak interactions between oil and water molecules cannot overcome the strong intermolecular hydrogen bonds holding the water molecules together.
Calculate the total heat required to completely melt 36.0 grams of ice at 0 degrees Celsius. (The molar heat of fusion for ice is 6.01 kJ/ mol, and the molar mass of water is 18.0 grams/mol)
12.02 kJ. First, convert grams to moles: 36.0 grams divided by 18.0 grams/mol equals 2.0 moles. Then calculate heat: 2.0 moles times 6.01 kJ/mol equals 12.02 kJ
Explain on a molecular level using Collision Theory why increasing the temperature of a reaction drastically increases the reaction rate.
Increasing the temperature increases the average kinetic energy of the molecules, causing them to move faster and collide more frequently. More importantly, it significantly increases the total number of molecules that possess enough energy to overcome the activation energy barrier during a collision, leading to a much higher percentage of successful collisions.
During a titration experiment, a student finds that 25.0 mL of an unknown concentration of HCI requires exactly 20.0 mL of 0.50 M NaOH to reach the equivalence point. What is the molarity of the acid?
0.40 M. Since it is a 1:1 reaction between HCI and NaOH, the moles of acid equal the moles of base. Multiplying 0.50 M by 20.0 mL gives 10 millimoles of base. Dividing 10 millimoles by 25.0 mL gives 0.40 M for the acid.