Chemistry Exam Review Flashcards

Significant figures indicate measurement precision.
Rules: All non-zero digits, zeros between non-zeros, and trailing zeros after a decimal point are significant. Leading zeros and trailing zeros without a decimal point (unless specified) are not significant.
Examples: $45.6$ (3 sig figs), $1002$ (4 sig figs), $0.0045$ (2 sig figs), $2.300$ (4 sig figs), $1500$ (2 sig figs), and $1500.$ (4 sig figs).
Multiplication/Division: The answer must match the fewest significant figures of the measurements used.
Addition/Subtraction: The answer must match the least precise decimal place of the measurements used.

Proton: $+1$ charge; located in the nucleus; mass is approximately $1\,amu$ .
Neutron: $0$ charge; located in the nucleus; mass is approximately $1\,amu$ .
Electron: $-1$ charge; located in the electron cloud; mass is approximately $0\,amu$ .
Atomic Number: Number of protons; defines the element identity.
Mass Number: Sum of protons and neutrons.
Neutron Calculation: $\text{Mass Number} - \text{Atomic Number} = \text{Number of Neutrons}$ .
Neutral Atoms: Protons equal electrons.
Ions: Cations (positive) lose electrons; Anions (negative) gain electrons.
Common Charges:
- Group 1: $+1$
- Group 2: $+2$
- Group 13: $+3$
- Group 15: $-3$
- Group 16: $-2$
- Group 17: $-1$
- Group 18: $0$

Horizontal rows: Periods; Vertical columns: Groups/Families.
Special Groups: Alkali Metals (Group 1), Alkaline Earth Metals (Group 2), Halogens (Group 17), Noble Gases (Group 18).
Elemental Divisions: Metals (left), Nonmetals (right), Metalloids (along the staircase).
Trends Across a Period (Left to Right): Atomic radius decreases; ionization energy and electronegativity increase.
Trends Down a Group: Atomic radius increases; ionization energy and electronegativity decrease.

Ionic Compounds: Metal + Nonmetal. Name the metal first, then the nonmetal with the suffix "-ide."
- Examples: $NaCl$ (sodium chloride), $MgO$ (magnesium oxide), $CaF_2$ (calcium fluoride).
- Transition Metals: Use Roman numerals for charge (e.g., $FeCl_2$ is iron(II) chloride; $FeCl_3$ is iron(III) chloride).
- Polyatomic Ions: Include $NO_3^-$ (nitrate), $NO_2^-$ (nitrite), $SO_4^{2-}$ (sulfate), $SO_3^{2-}$ (sulfite), $CO_3^{2-}$ (carbonate), $PO_4^{3-}$ (phosphate), $OH^-$ (hydroxide), and $NH_4^+$ (ammonium).
Covalent Compounds: Nonmetal + Nonmetal. Use numerical prefixes ( $mono-$ , $di-$ , $tri-$ , $tetra-$ , $penta-$ , $hexa-$ , $hepta-$ , $octa-$ , $nona-$ , $deca-$ ).
- Rules: The second element ends in "-ide"; omit "mono-" on the first element.
- Examples: $CO$ (carbon monoxide), $N_2O_4$ (dinitrogen tetroxide), $SF_6$ (sulfur hexafluoride).

Binary Acids ( $H$ + nonmetal): "Hydro-" + root + "-ic acid" (e.g., $HCl$ is hydrochloric acid).
Oxyacids (Anion-based):
- "-ate" anion becomes "-ic acid" (e.g., $HNO_3$ is nitric acid; $H_2SO_4$ is sulfuric acid).
- "-ite" anion becomes "-ous acid" (e.g., $HNO_2$ is nitrous acid; $H_2SO_3$ is sulfurous acid).
- Phosphate ( $PO_4^{3-}$ ) becomes phosphoric acid ( $H_3PO_4$ ).

Law of Conservation of Mass: Matter is neither created nor destroyed; balance equations using coefficients only.
Synthesis: $A + B \rightarrow AB$
Decomposition: $AB \rightarrow A + B$
Single Replacement: $A + BC \rightarrow AC + B$
Double Replacement: $AB + CD \rightarrow AD + CB$
Combustion: $\text{Hydrocarbon} + O_2 \rightarrow CO_2 + H_2O$

Always Soluble: Group 1 compounds, $NH_4^+$ , $NO_3^-$ , and Acetates ( $C_2H_3O_2^-$ ).
Usually Soluble: $Cl^-$ , $Br^-$ , $I^-$ . Exceptions: $Ag^+$ , $Pb^{2+}$ , Hg_2^{2+}$.\n- **Usually Insoluble**: CO_3^{2-} $,$ PO_4^{3-} $,$ OH^- $,$ S^{2-} $. Exceptions: Group 1 ions and$ NH_4^+.\n\n# Stoichiometry\n\n- **Mole**: 6.022 \times 10^{23} particles.\n- **Conversions**:\n - \text{moles} = \text{grams} \div \text{molar mass}\n - \text{grams} = \text{moles} \times \text{molar mass}\n- **Common Molar Masses**: H_2O = 18.0\,g\,mol^{-1} $,$ CO_2 = 44.0\,g\,mol^{-1} $,$ NaCl = 58.44\,g\,mol^{-1}$$.
Stoichiometry Steps: Balance equation, convert grams to moles, use mole ratios from coefficients, and convert back to grams if required.