General Chemistry Unit 1 Study Guide

Flashcards covering general chemistry topics including measurement accuracy, uncertainty propagation, equilibrium constants, thermodynamics, and acid-base chemistry.

Significant Figures

Indicate the accuracy (degree of reliability) of a given scientific measurement; rules include all nonzero digits are significant and zeroes between nonzero digits are significant.

Precision

Describes the reproducibility of a result, or how closely measurements of the same quantity agree with one another.

Accuracy

Describes how close a measured value is to the "true" value or a known standard.

Systematic Error

Also called determinate error, it arises from a flaw in equipment or experimental design and is fundamentally reproducible and correctable.

Random Error

Also called indeterminate error, it arises from uncontrolled variables and has an equal chance of being positive or negative; it cannot be completely eliminated.

Absolute Uncertainty

Expresses the margin of uncertainty associated with a measurement, such as $\pm 0.02\,mL$.

Relative Uncertainty

Compares the size of the absolute uncertainty with the size of its associated measurement; defined as $\frac{\text{absolute uncertainty}}{\text{magnitude of measurement}}$.

Arithmetic Mean ($\bar{x}$)

The sum of measured values divided by $n$, the number of measurements.

Standard Deviation ($s$)

A measure of how closely data are clustered about the mean; defined by the formula $\sqrt{\frac{\sum (x_i - \bar{x})^2}{n - 1}}$.

Student’s t

A statistical tool used to express confidence intervals and compare results from different experiments.

Confidence Interval

An expression stating that the true mean ($\mu$) is likely to lie within a certain distance from the measured mean, calculated as $\mu = \bar{x} \pm \frac{ts}{\sqrt{n}}$.

Degrees of Freedom ($f$)

A value used in statistical calculations, equal to $n - 1$.

Equilibrium Constant ($K$)

For a reaction $aA + bB \rightleftharpoons cC + dD$, it is defined by the law of mass action as $K = \frac{[C]^c[D]^d}{[A]^a[B]^b}$.

Enthalpy Change ($\Delta H$)

The heat absorbed or released when a reaction takes place under constant pressure.

Exothermic

A reaction where the change in enthalpy ($\Delta H$) is negative, indicating heat is released.

Endothermic

A reaction where the change in enthalpy ($\Delta H$) is positive, indicating heat is absorbed.

Entropy ($S$)

A measure of possible arrangements, freedom, or disorder within a substance; generally $S_{\text{gas}} > S_{\text{liquid}} > S_{\text{solid}}$.

Gibbs Free Energy ($\Delta G$)

A thermodynamic property used to determine spontaneity; defined as $\Delta G = \Delta H - T\Delta S$.

Spontaneous Reaction

A chemical reaction driven in the forward direction, characterized by $\Delta G < 0$.

Le Chatelier’s Principle

States that if a system at equilibrium is subjected to a stressor, the system proceeds in a direction that offsets the change.

Reaction Quotient ($Q$)

Has the same form as the equilibrium constant ($K$) but uses concentrations existing at any time away from equilibrium.

Solubility Product ($K_{sp}$)

The equilibrium constant for a reaction in which a solid salt dissolves into its constituent ions.

Common Ion Effect

The reduction in solubility of an ionic compound when a soluble compound containing one of its constituent ions is added to the solution.

Autoprotolysis

Self-ionization of water where it acts as both an acid and a base: $H_2O(l) \rightleftharpoons H^+(aq) + OH^-(aq)$ with $K_w = 1.0 \times 10^{-14}$ at $25^{\circ}C$.

Bronsted-Lowry Acid

A species that acts as a proton ($H^+$) donor.

Bronsted-Lowry Base

A species that acts as a proton ($H^+$) acceptor.

Conjugate Acid-Base Pair

Two species related to each other by the gain or loss of a single proton ($H^+$).

Amphoteric

A species, such as $HA^-$, that can behave as either an acid or a base.

Salt

An ionic solid, usually comprising a cation-anion pair, which can be thought of as the product of an acid-base reaction.

Characteristic and Mantissa

The two parts of a logarithm; the characteristic is the integer part and the mantissa is the decimal part.