AEPA Chemistry NT306 flashcards
AEPA Chemistry NT306 · Build recall with a focused review session.
33 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Independent variable
- The factor deliberately changed or manipulated by the experimenter in a controlled investigation; its effect on the measured dependent variable is what the experiment tests.
- Accuracy versus precision
- Accuracy describes how close a measurement is to the true value, while precision describes how closely repeated measurements agree with one another.
- Scientific theory
- A broad, well-supported explanation of natural phenomena built from many tested hypotheses and consistent evidence, not a mere guess or speculation.
- Percent error formula
- Percent error equals the absolute difference between experimental and accepted values divided by the accepted value, multiplied by one hundred.
- Significant figures rules
- Count all nonzero digits and interior zeros; leading zeros never count; trailing zeros count only when a decimal point is present in the number.
- Falsifiability
- A property of a scientific hypothesis meaning it makes a specific prediction that could be contradicted by observable evidence if the claim were wrong.
- Homogeneous versus heterogeneous
- A homogeneous mixture has uniform composition and a single visible phase, while a heterogeneous mixture has nonuniform composition with distinguishable parts or phases.
- Intensive versus extensive properties
- Intensive properties such as density and boiling point do not depend on sample size; extensive properties such as mass and volume do depend on amount.
- Density relationship
- Density equals mass divided by volume; an object floats in a fluid denser than itself and sinks in a fluid less dense than itself.
- Distillation separation
- A separation technique that boils a liquid mixture and condenses the vapor, exploiting differences in boiling points to isolate components.
- Diatomic elements list
- The seven elements that exist as diatomic molecules under standard conditions: hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine.
- Molar mass
- The mass in grams of one mole of a substance, numerically equal to the sum of atomic masses in its formula expressed in grams per mole.
- Percent composition by mass
- The mass of a given element in one mole of a compound divided by the compound's molar mass, multiplied by one hundred.
- Balancing chemical equations
- Adjust coefficients only, never subscripts, so the number of atoms of each element is identical on reactant and product sides.
- Net ionic equation
- A chemical equation showing only the ions and molecules that actually change during a reaction, with spectator ions omitted from both sides.
- Solubility rule for chlorides
- Most chloride salts dissolve in water, but chlorides of silver, lead, and mercury are insoluble exceptions commonly tested.
- pH and pOH relation
- pH equals the negative logarithm of hydrogen ion concentration; pH plus pOH equals fourteen in aqueous solution at twenty-five degrees Celsius.
- Oxidation and reduction
- Oxidation is loss of electrons and an increase in oxidation number; reduction is gain of electrons and a decrease in oxidation number.
- Limiting reactant
- The reactant completely consumed first in a reaction; its amount determines the maximum quantity of product that can form.
- Percent yield
- The actual measured product mass divided by the theoretical maximum product mass predicted from stoichiometry, multiplied by one hundred.
- First law of thermodynamics
- Energy cannot be created or destroyed; the change in internal energy equals heat added plus work done on the system.
- Hess's law
- The overall enthalpy change of a reaction equals the sum of enthalpy changes for any sequence of steps leading from reactants to products.
- Exothermic versus endothermic
- Exothermic reactions release heat and have negative enthalpy change; endothermic reactions absorb heat and have positive enthalpy change.
- Calorimetry equation
- Heat transferred equals mass times specific heat capacity times temperature change, written q equals mc delta T for a substance being heated or cooled.
- Gibbs free energy criterion
- A reaction is spontaneous when the change in Gibbs free energy is negative, calculated as enthalpy change minus temperature times entropy change.
- Catalyst effect
- A catalyst lowers activation energy and increases reaction rate for both forward and reverse directions without being consumed or changing enthalpy.
- Le Chatelier's principle
- When a stress such as concentration, pressure, or temperature change is applied to a system at equilibrium, the system shifts to partially offset that stress.
- Atomic number and mass number
- Atomic number counts protons and identifies the element; mass number counts protons plus neutrons and distinguishes isotopes of that element.
- Hund's rule
- Within a subshell, electrons fill degenerate orbitals singly with parallel spins before any orbital receives a second electron.
- Periodic atomic radius trend
- Atomic radius generally decreases left to right across a period as nuclear charge grows, and increases top to bottom down a group as shells are added.
- VSEPR theory
- Electron pairs around a central atom repel and arrange to maximize separation; lone pairs repel more strongly, compressing bond angles below ideal values.
- Hydrogen bonding
- An unusually strong dipole attraction occurring when hydrogen bonded to nitrogen, oxygen, or fluorine interacts with a lone pair on another electronegative atom.
- Molecular polarity
- A molecule is polar when bond dipoles do not cancel; symmetric geometry with identical bonds can cancel dipoles and produce a nonpolar molecule.