General Chemistry 115: Exam 1B Study Guide

General Chemistry Fundamentals

Unit Conversions and Useful Equations

Understanding unit conversions and basic equations is essential for solving problems in general chemistry. These tools allow you to switch between different measurement systems and calculate properties of matter.

• Density (D): Defined as mass per unit volume. $D = \frac{\text{mass}}{\text{volume}}$

• Volume of a Sphere: $V = \frac{4}{3} \pi r^3$ where $\pi = 3.141592$

• Common Conversions:

  • 1 mile = 5280 feet

  • 1 foot = 12 inches

  • 1 inch = 2.54 cm

  • 1 liter = 1.05669 quarts

  • 1 mile = 1.60934 km

  • 1000 mg = 1 g

  • 1 mL = 1 cm3

Chemical Nomenclature

Names and Symbols of Elements, Ions, and Compounds

Chemical nomenclature is the system used to name chemical substances. It is important to know both the names and formulas of common compounds and ions.

• Examples:

  • Na2SO4: Sodium sulfate

  • HCO3-: Hydrogen carbonate (bicarbonate)

  • Ad(CO)3: Additional info: Possibly a typo; could refer to a metal carbonyl complex.

  • HBr(aq): Hydrobromic acid

  • Copper(II) perchlorate: Cu(ClO4)2

  • Strontium oxide: SrO

  • Calcium nitrite: Ca(NO2)2

• General Rules:

  • For ionic compounds, name the cation first, then the anion.

  • For acids, use the prefix 'hydro-' for binary acids and '-ic' or '-ous' for oxyacids depending on the anion.

  • Polyatomic ions have specific names (e.g., sulfate SO42-, nitrate NO3-).

Significant Figures

Counting Significant Figures

Significant figures reflect the precision of a measured or calculated quantity. Knowing how to count them is crucial for reporting scientific data.

• Rules for Significant Figures:

  • All nonzero digits are significant.

  • Zeros between nonzero digits are significant.

  • Leading zeros are not significant.

  • Trailing zeros in a decimal number are significant.

• Examples:

  • 1.057 × 104: 4 significant figures

  • 0.00230122: 6 significant figures

  • 13.3 × 102: 3 significant figures

  • 0.00048: 2 significant figures

  • 499.100: 6 significant figures

Chemical Formulas

Writing Formulas for Compounds

Writing correct chemical formulas requires knowledge of the charges and combining ratios of ions and elements.

• Tetraphosphorous decoxide: P4O10

• Potassium sulfate: K2SO4

• Barium chlorate: Ba(ClO3)2

• Sulfur dioxide: SO2

• Magnesium chloride: MgCl2

Solution Concentration

Calculating Molarity

Molarity (M) is a measure of the concentration of a solute in a solution, defined as moles of solute per liter of solution.

• Formula: $M = \frac{\text{moles of solute}}{\text{liters of solution}}$

• Example Calculation:

  • Given: 26.0 g of BaCl2 (molar mass = 208.2 g/mol) dissolved in 450.0 mL of solution.

  • Convert grams to moles: $\frac{26.0\ \text{g}}{208.2\ \text{g/mol}} = 0.125\ \text{mol}$

  • Convert mL to L: $450.0\ \text{mL} = 0.4500\ \text{L}$

  • Calculate molarity: $M = \frac{0.125}{0.4500} = 0.278\ \text{M}$

HTML Table: Common Polyatomic Ions

Polyatomic ions are ions composed of two or more atoms covalently bonded, carrying a net charge. Knowing their names and formulas is essential for nomenclature and formula writing.

Name	Formula	Charge
Sulfate	SO4	2-
Chlorate	ClO3	1-
Perchlorate	ClO4	1-
Nitrite	NO2	1-
Carbonate	CO3	2-
Phosphate	PO4	3-

Additional info:

• Some compound names and formulas may be inferred based on standard chemical nomenclature.

• Ad(CO)3 is not a standard compound; possibly a typo or reference to a metal carbonyl complex.