Survey of Chem Exam 3

What is molar mass?

The mass of one mole of a substance, measured in grams per mole (g/mol).

How do you calculate molar mass?

Add the atomic masses of all atoms in the chemical formula, multiplying each atomic mass by its subscript.

What is a mole?

A unit of measurement representing 6.022 × 10²³ particles of a substance.

What is Avogadro's number?

6.022 × 10²³ particles per mole.

How do you convert moles to particles?

Multiply moles by Avogadro's number (6.022 × 10²³).

How do you convert particles to moles?

Divide the number of particles by Avogadro's number (6.022 × 10²³).

How do you calculate moles from mass?

Divide mass in grams by molar mass (g/mol).

How do you calculate mass from moles?

Multiply moles by molar mass (g/mol).

What is the difference between coefficients and subscripts?

Coefficients represent the number of molecules or formula units; subscripts represent the number of atoms of an element in a formula.

What are reactants?

The starting substances in a chemical reaction; written on the left side of an equation.

What are products?

The substances formed during a chemical reaction; written on the right side of an equation.

What is a balanced chemical equation?

An equation with equal numbers of each type of atom on both sides.

How do you balance a chemical equation?

Adjust coefficients until each element has the same number of atoms on both sides. Never change subscripts.

What are the five common types of chemical reactions?

Synthesis, decomposition, single replacement, double replacement, and combustion.

What is a synthesis reaction?

Two or more substances combine to form one product. A + B → AB.

What is a decomposition reaction?

One compound breaks down into two or more simpler substances. AB → A + B.

What is a single replacement reaction?

One element replaces another element in a compound. A + BC → AC + B.

What is a double replacement reaction?

Two compounds exchange ions to form two new compounds. AB + CD → AD + CB.

What is a combustion reaction?

A substance reacts with oxygen, releasing energy. Hydrocarbon combustion typically produces carbon dioxide and water.

What is oxidation?

The loss of electrons; oxidation number increases.

What is reduction?

The gain of electrons; oxidation number decreases.

What is actual yield?

The amount of product actually obtained from a chemical reaction.

What is theoretical yield?

The maximum amount of product that can be produced based on the limiting reactant.

What is percent yield?

The percentage of theoretical yield that was actually obtained.

What is the formula for percent yield?

Percent yield = (Actual yield ÷ Theoretical yield) × 100%.

How do you determine theoretical yield?

Use a balanced chemical equation and mole ratios to calculate the maximum amount of product.

How do you obtain quantitative information from a balanced chemical equation?

Use the coefficients as mole ratios to calculate the amounts of reactants consumed and products produced.

What is stoichiometry?

The calculation of quantitative relationships between reactants and products in a balanced chemical equation.

What is thermodynamics?

The study of energy, heat, and their relationship to chemical and physical changes.

What is chemical kinetics?

The study of the rates of chemical reactions and the factors that affect those rates.

What is activation energy?

The minimum energy required for reactants to begin a chemical reaction.

What factors affect chemical reaction rates?

Temperature, concentration, surface area, catalysts, and the nature of the reactants.

What is the difference between calories and Calories?

A calorie (cal) is a small unit of energy. A Calorie (Cal) is a kilocalorie (kcal), equal to 1,000 calories.

How do you calculate the Calorie content of food?

Multiply carbohydrates and protein grams by 4 Cal/g and fat grams by 9 Cal/g, then add the results.

What are common units of energy measurement?

Joules (J), kilojoules (kJ), calories (cal), and kilocalories (kcal or Cal).

How do you convert between energy units?

1 kJ = 1,000 J; 1 cal = 4.184 J; 1 kcal = 1,000 cal = 1 Cal.

What is the first law of thermodynamics?

Energy cannot be created or destroyed; it can only be transferred or transformed.

What is an endothermic reaction?

A reaction that absorbs heat from its surroundings. ΔH is positive.

What is an exothermic reaction?

A reaction that releases heat into its surroundings. ΔH is negative.

What does an energy diagram show?

Energy changes during a chemical reaction, including reactant energy, product energy, activation energy, and enthalpy change (ΔH).

What is the equilibrium constant (K)?

A value representing the ratio of product concentrations to reactant concentrations at equilibrium, with concentrations raised to their coefficients.

What does a large equilibrium constant (K > 1) indicate?

Products are favored at equilibrium.

What does a small equilibrium constant (K < 1) indicate?

Reactants are favored at equilibrium.

What does an equilibrium constant near 1 indicate?

Neither reactants nor products are strongly favored.

What is chemical equilibrium?

A dynamic state in which forward and reverse reaction rates are equal and concentrations remain constant.

What is Le Châtelier's Principle?

When a system at equilibrium is disturbed, it shifts in the direction that counteracts the disturbance.

What happens when the concentration of a reactant increases at equilibrium?

Equilibrium shifts toward the products.

What happens when the concentration of a product increases at equilibrium?

Equilibrium shifts toward the reactants.

What happens when pressure increases in a gaseous equilibrium system?

Equilibrium shifts toward the side with fewer moles of gas.

How do intermolecular forces affect melting and boiling points?

Stronger intermolecular forces generally produce higher melting and boiling points because more energy is needed to separate particles.

What is pressure?

Force exerted per unit area.

What are common pressure units?

Atmospheres (atm), millimeters of mercury (mmHg), torr, kilopascals (kPa), and pounds per square inch (psi).

What are common pressure conversions?

1 atm = 760 mmHg = 760 torr = 101.325 kPa = 14.7 psi.

What are the six changes of state?

Melting (solid to liquid), freezing (liquid to solid), vaporization (liquid to gas), condensation (gas to liquid), sublimation (solid to gas), and deposition (gas to solid).

What is a heating curve?

A graph showing how temperature changes as heat is added to a substance, including phase changes.

What do flat sections of a heating curve represent?

Phase changes during which temperature remains constant while energy is used to overcome intermolecular forces.

What is the formula for heat during a phase transition?

q = m × ΔH, where q is heat, m is mass, and ΔH is heat of fusion or vaporization.

How do you calculate heat during a temperature change?

q = m × c × ΔT, where m is mass, c is specific heat, and ΔT = final temperature − initial temperature.

What is the ideal gas law?

PV = nRT; relates pressure, volume, moles, and temperature.

What is the combined gas law?

P₁V₁/T₁ = P₂V₂/T₂; relates pressure, volume, and temperature when the amount of gas remains constant.

What is Boyle's Law?

Pressure and volume are inversely proportional when temperature and moles remain constant.

What is Charles's Law?

Volume and temperature are directly proportional when pressure and moles remain constant.

What is Gay-Lussac's Law?

Pressure and temperature are directly proportional when volume and moles remain constant.

What is Avogadro's Law?

Volume and number of moles are directly proportional when pressure and temperature remain constant.

What temperature must be used in gas law calculations?

Kelvin. K = °C + 273.15.

What are the properties of a gas at STP?

0°C (273.15 K) and 1 atm pressure. One mole of an ideal gas occupies approximately 22.4 L.

How do you calculate the density of a gas at STP?

Density = molar mass ÷ 22.4 L/mol, expressed in g/L.

What is Dalton's Law of Partial Pressures?

The total pressure of a gas mixture equals the sum of the individual partial pressures. Ptotal = P₁ + P₂ + P₃.

What is a homogeneous mixture?

A mixture with a uniform composition throughout; components are evenly distributed.

What is a heterogeneous mixture?

A mixture with a nonuniform composition in which different parts or phases can be distinguished.

What is a solute?

The substance that gets dissolved in a solution.

What is a solvent?

The substance that dissolves the solute, usually present in the greatest amount.

What are the three common types of solutions based on saturation?

Unsaturated: can dissolve more solute. Saturated: contains the maximum amount at a given temperature. Supersaturated: contains more dissolved solute than normally possible at that temperature.

What is solubility?

The ability of a substance to dissolve in a particular solvent.

What generally happens to the solubility of ionic compounds in water?

Many ionic compounds dissolve in water, but solubility depends on the specific ions.

What generally happens to the solubility of covalent compounds?

Polar covalent compounds tend to dissolve in polar solvents, while nonpolar covalent compounds tend to dissolve in nonpolar solvents.

What is the rule "like dissolves like"?

Polar substances dissolve in polar solvents, and nonpolar substances dissolve in nonpolar solvents.

What is an electrolyte?

A substance that produces ions when dissolved in water or melted and can conduct electricity.

What is a strong electrolyte?

A substance that completely dissociates or ionizes into ions in solution and conducts electricity strongly.

What is a weak electrolyte?

A substance that partially ionizes into ions in solution and conducts electricity weakly.

What is a nonelectrolyte?

A substance that dissolves without forming ions and does not conduct electricity.

What is a hydration equation?

A chemical equation showing an ionic compound separating into its ions in water.

How do you write a balanced hydration equation?

Write the ionic compound as separated aqueous ions, ensuring the number of each ion and total charge are balanced.

What is molarity (M)?

The number of moles of solute per liter of solution. M = moles of solute ÷ liters of solution.

What is mass percent concentration?

Mass of solute ÷ total mass of solution × 100%.

What is volume percent concentration?

Volume of solute ÷ total volume of solution × 100%.

What is mass/volume percent concentration?

Mass of solute in grams ÷ volume of solution in milliliters × 100%.

What is the formula for dilution calculations?

M₁V₁ = M₂V₂, where M₁ and V₁ are initial concentration and volume and M₂ and V₂ are final concentration and volume.

What happens to concentration during dilution?

Concentration decreases as solvent is added, but the amount of solute remains constant.

What is a dosage calculation?

A calculation used to determine the correct amount of medication or substance to administer based on a prescribed dose and available concentration.

How do you solve dosage calculations?

Amount to administer = Desired dose ÷ Dose available × Quantity available.

What is dimensional analysis?

A problem-solving method that uses conversion factors and unit cancellation to convert between different units.

What is a chemical change or chemical reaction?

The transformation of elements or compounds into different elements or compounds.

What happens during a chemical reaction?

Existing chemical bonds break and new chemical bonds form as reactants are converted into products.

What is the foundation of chemistry?

Chemical reactions, which involve the breaking of existing bonds and the formation of new bonds.

In what proportions do atoms, ions, and molecules undergo reactions?

Whole-number proportions.

How are the number of particles in a sample related to its mass?

The mass of a sample is related to the number of particles it contains because each particle has a measurable mass.

What is an atomic mass unit (amu)?

A unit used to report the mass of a single atom, molecule, or formula unit.

What is molecular mass?

The sum of the individual average atomic masses of all atoms in a molecule.

How do you calculate molecular mass?

Add the atomic masses of all atoms in the molecular formula, multiplying each atomic mass by its subscript.