Chemistry Final Review

What does VSEPR stand for?

Valence-Shell Electron Pair Repulsion Theory

What shape do molecules with two atoms have?

Linear

What is the bond angle in a trigonal planar molecule?

120 degrees

What is the bond angle in a tetrahedral molecule?

109.5 degrees

What characterizes a trigonal pyramidal molecular shape?

One central atom with three atoms attached and a pair of unshared electrons.

What is a bent molecular shape?

A central atom with two atoms attached and two pairs of unshared electrons.

What is the bond angle in an octahedral molecule?

90 and 180 degrees

What is the definition of bond length?

The distance between bonded atoms; larger atoms have longer bond lengths.

What is a polar covalent bond?

An unequal sharing of electrons due to the presence of an electronegative atom.

What is the significance of diatomic elements?

They exist as pairs when alone (e.g., N2, O2, F2, etc.).

What is a chemical reaction?

A process where the physical and chemical properties of substances change as new substances are formed.

What are reactants in a chemical reaction?

Substances that enter into a chemical reaction.

What are products in a chemical reaction?

Substances that are produced by a chemical reaction.

What does the law of conservation of matter state?

The mass before and after a reaction must remain the same.

What is a chemical equation?

A representation of a chemical reaction using symbols and formulas.

What is the difference between a word equation and a formula equation?

A word equation uses names of substances, while a formula equation uses chemical symbols.

What is a direct combination reaction?

A reaction where two or more reactants combine to form a single product.

What is a decomposition reaction?

A reaction where a compound breaks down into smaller parts.

What is a single-replacement reaction?

A reaction where an uncombined element displaces an element in a compound.

What is a double-replacement reaction?

A reaction where atoms or ions from two different compounds exchange places.

What is a combustion reaction?

A reaction that occurs when a substance burns in the presence of oxygen.

What is Avogadro's number?

6.02 x 10^23, the number of particles in one mole.

What is the formula mass?

The sum of the atomic masses of all atoms in a compound.

What is the significance of hybrid orbitals?

They change shape during bonding depending on the shape of the molecule.

What is the bond angle in a square planar molecule?

90 degrees.

What is the general formula for a direct combination reaction?

A + B → AB

What is the general formula for a decomposition reaction?

AB → A + B

What is the general formula for a single-replacement reaction?

A + BX → AX + B

What is the general formula for a double-replacement reaction?

AX + BY → AY + BX

What is the general formula for a combustion reaction?

Fuel + O2 → CO2 + H2O

What is the number of atoms in 1 mole of an element?

6.02 x 10^23 atoms

How many molecules are in 1 mole of a covalently bonded molecule?

6.02 x 10^23 molecules

What is molar mass?

The mass in grams of 1 mole of a substance.

What is the relationship between moles and grams?

1 mole = _____ grams (depends on the substance).

What is the molar volume of a gas at STP?

1 mole = 22.4 L

What is the empirical formula?

The smallest ratio of elements in a compound.

How do you find the percent composition of an element?

Mass of the element divided by the molar mass, multiplied by 100%.

How do you find the molecular formula from the empirical formula?

Divide the molar mass by the empirical formula mass and multiply the subscripts.

What is stoichiometry?

The study of quantitative relationships in chemical formulas and reactions.

What is a mole-to-mole ratio?

The ratio of moles of one substance to moles of another in a balanced equation.

What is a limiting reactant?

The reactant that limits the amount of product formed in a reaction.

How do you calculate percent yield?

Percent Yield = (actual yield / expected yield) x 100

What is the expected yield in a chemical reaction?

The amount of product predicted by stoichiometric calculations.

What is the actual yield?

The amount of product actually produced in a lab experiment.

Can you ever get over 100% yield?

Yes, but it usually indicates human error.

How do you determine the limiting reactant?

Perform mass-to-mass calculations for each reactant to the same product and compare the results.

What is thermochemistry?

The study of changes in heat in chemical reactions.

What does 'thermo' mean?

Heat.

What type of reaction absorbs heat?

Endothermic reactions.

In an endothermic reaction, how is energy treated?

As a reactant.

What is an example of an endothermic reaction?

The dissolution of NH4NO3 in water.

What type of reaction releases heat?

Exothermic reactions.

In an exothermic reaction, how is energy treated?

As a product.

What is the goal of every chemical reaction?

To become more stable and less energetic.

What is enthalpy (H)?

The heat absorbed or released in a reaction.

What does ΔH represent?

The change in enthalpy, calculated as H Products - H Reactants.

When is ΔH positive?

When the enthalpy of the products is higher than that of the reactants.

What does a positive ΔH indicate?

An endothermic reaction.

What does a negative ΔH indicate?

An exothermic reaction.

What is Hess's Law?

The principle that the total enthalpy change for a reaction is the sum of the enthalpy changes for each step.

What happens to ΔH when a reaction is reversed?

The sign of ΔH changes.

What is calorimetry?

The study of heat flow and heat measurements.

What does specific heat measure?

The heat capacity of 1 gram of a substance.

What is the unit for specific heat?

J/g ºC.

What is the equation for heat of the surroundings?

qsur = mCΔT.

What is the relationship between qrxn and qsur?

qrxn = - qsur.

What is the definition of heat?

The transfer of kinetic energy from a hotter object to a colder object.

What is the Kinetic Molecular Theory (KMT)?

A theory that describes the behavior of gases in terms of particles in constant motion.

What is Boyle's Law?

The relationship between pressure and volume of a gas at constant temperature, expressed as PV = K.

What does Charles's Law state?

Volume and temperature are directly related at constant pressure.

What is Avogadro's Law?

Equal volumes of gases at the same temperature and pressure contain the same number of particles.

What is the Ideal Gas Law?

PV = nRT, where R is the universal gas constant.

What is STP in terms of gases?

Standard Temperature and Pressure, defined as 1 atm and 273 K.

What does KMT stand for?

Kinetic Molecular Theory.

What are real gases?

Gases that do not perfectly follow the ideal gas law, especially at extreme temperatures and pressures.

What is the lifting power of gases in balloons and blimps attributed to?

The gases inside these objects being less dense than the air around them.

What is gas effusion?

The process of a gas traveling through a tiny hole one particle at a time.

What are condensed states of matter?

States that refer to solids and liquids, which have higher densities than gases.

What determines the state of a substance at room temperature?

The strength of the attractions between its particles (intermolecular forces).

What are the three types of intermolecular forces?

Hydrogen bonding, dipole-dipole interactions, and London dispersion forces.

What is hydrogen bonding?

A strong intermolecular force occurring when hydrogen is bonded to highly electronegative atoms like F, N, or O.

What are London dispersion forces?

The weakest intermolecular force caused by temporary shifts in electron clouds around molecules.

What is viscosity?

A measure of a liquid's resistance to flow, influenced by intermolecular forces.

What is surface tension?

The resistance of a liquid to increase its surface area, related to the strength of intermolecular forces.

What is a crystalline solid?

A solid with a highly regular arrangement of its atoms.

What are ionic solids?

Solids made up of ions held together by strong electrostatic forces.

What is the difference between molecular solids and atomic solids?

Molecular solids are made of molecules, while atomic solids consist of pure elements in solid form.

What is sublimation?

The phase change where a substance goes directly from a solid to a gas.

What is solvation?

The interaction between solute and solvent particles.

What is molarity?

A measure of concentration defined as moles of solute per liter of solution.

What is a saturated solution?

A solution containing the maximum possible amount of dissolved solute at equilibrium.

What are colligative properties?

Properties that depend on the amount of dissolved solute but not on its chemical identity.

What is vapor-pressure lowering?

A colligative property where the vapor pressure of a solution is lower than that of the pure solvent.

What is boiling-point elevation?

A colligative property that describes the increase in boiling point of a solution compared to the pure solvent.

What is freezing-point depression?

A colligative property that describes the decrease in freezing point of a solution compared to the pure solvent.

What is the van't Hoff factor?

A factor used in colligative property calculations that accounts for the number of particles a solute dissociates into.

What is the heat of vaporization?

The amount of energy needed to convert a liquid into a gas at its boiling point.

What is the heat of fusion?

The amount of energy needed to convert a solid into a liquid at its melting point.

What is hydration?

Solvation when the solvent is water.

What does 'like dissolves like' mean?

A principle stating that polar solvents dissolve polar solutes, and nonpolar solvents dissolve nonpolar solutes.