General Chemistry Exam Study Guide: Key Concepts, Equations, and Problem-Solving Strategies

Directions and Exam Format

Exam Structure and Instructions

This exam consists of multiple-choice, true/false, fill-in-the-blank, and free-response questions. Students are required to show all work for full credit, use dimensional analysis, and follow specific instructions for calculator and Scantron use.

• Free Response: Show all work for full credit.

• Multiple Choice: Select the appropriate response(s).

• True/False: Write the complete word in the space provided.

• Fill in the Blank: Write the correct answer in the space provided.

• Calculator Policy: Only non-programmable, non-graphing calculators are allowed.

• Electronic Devices: All electronic devices other than your calculator are prohibited.

Essential Equations and Constants

Temperature Conversions

• Celsius to Fahrenheit: $^\circ F = \frac{9}{5} (^\circ C) + 32$

• Fahrenheit to Celsius: $^\circ C = \frac{5}{9} (^\circ F - 32)$

• Celsius to Kelvin: $K = ^\circ C + 273.15$

• Kelvin to Celsius: $^\circ C = K - 273.15$

Volume Formulas

• Sphere: $V_{\text{sphere}} = \frac{4}{3} \pi r^3$

• Cylinder: $V_{\text{cylinder}} = \pi r^2 h$

• Cube: $V_{\text{cube}} = l^3$

• Rectangular Solid: $V_{\text{solid}} = lwh$

Density

• $\text{Density} = \frac{\text{mass}}{\text{volume}}$

Atomic Mass Calculation

• $\text{atomic mass} = \sum (\text{fractional abundance} \times \text{mass})_{\text{isotope}}$

Conversion Factors

• 1 L = 1.0567 qt

• 1 gal = 4 qt

• 1 kg = 2.2046 lb

• 1 lb = 453.59 g

• 1 in = 2.54 cm

• 1 metric ton = 1000 kg

• 1 km = 0.62137 mi

• 4 cups = 1 qt

Constants

• $\pi = 3.1416$

• Avogadro's number: $N_A = 6.022 \times 10^{23} \text{mol}^{-1}$

Key Concepts in General Chemistry

Atoms, Ions, and Compounds

Atoms are the basic units of matter, consisting of protons, neutrons, and electrons. In compounds, cations and anions combine so that the overall charge is zero.

• Cations: Positively charged ions (loss of electrons).

• Anions: Negatively charged ions (gain of electrons).

• Compounds: Substances formed from two or more elements in fixed ratios.

Physical and Chemical Properties

• Ductility: Ability to be drawn into a thin wire.

• Heterogeneous Mixture: Mixture that can scatter light, e.g., a colloid.

• Condensation: Phase change from gas to liquid.

Balanced Chemical Equations

Balancing chemical equations ensures the conservation of mass and charge. Each side of the equation must have the same number of atoms of each element.

• Example: $\text{AlCl}_3(aq) + \text{NH}_4\text{PO}_4(aq) \rightarrow \text{AlPO}_4(s) + 3 \text{NH}_4\text{Cl}(aq)$

Stoichiometry and Limiting Reactants

Stoichiometry involves calculating the quantities of reactants and products in chemical reactions. The limiting reactant is the reactant that is completely consumed first, limiting the amount of product formed.

• Example: If 50.0 g S and 105.0 g F2 react to form SF6, the excess reactant can be determined by stoichiometric calculations.

Significant Figures

Significant figures reflect the precision of a measurement. The number of significant figures in a value is determined by counting all digits except leading zeros.

• Example: 3400 has 2 significant figures.

Density Calculations

Density is a physical property defined as mass per unit volume.

• Formula: $\text{Density} = \frac{\text{mass}}{\text{volume}}$

• Example: A metal weighing 45.42 g with a volume of 5.10 mL has a density of $8.91 \text{g/cm}^3$.

Temperature Scales

Temperature can be measured in Celsius, Fahrenheit, or Kelvin. Kelvin is the SI unit for temperature.

• Highest temperature: 274 °C is higher than 274 K or 274 °F.

Molecular and Empirical Formulas

The empirical formula shows the simplest whole-number ratio of elements in a compound, while the molecular formula shows the actual number of atoms of each element in a molecule.

• Example: Empirical formula for a hydrocarbon: $\text{CH}_2$; molecular formula: $\text{C}_4\text{H}_8$.

Atomic Structure

Atoms consist of protons, neutrons, and electrons. The atomic number equals the number of protons; the mass number equals protons plus neutrons.

• Example: $^{58}_{29}\text{Cu}$ has 29 protons, 29 electrons, and 36 neutrons.

Isotopes

Isotopes are atoms of the same element with different numbers of neutrons.

• Example: $^{23}\text{Na}$ and $^{24}\text{Na}$ are isotopes of sodium.

Calculating Atomic Mass from Isotopic Abundance

The atomic mass of an element is calculated using the weighted average of the masses of its isotopes.

• Formula: $\text{atomic mass} = \sum (\text{fractional abundance} \times \text{mass})_{\text{isotope}}$

• Example: Silver: $108.19 \text{ amu}$

Percent Composition and Empirical Formula

Percent composition is the percentage by mass of each element in a compound. The empirical formula is determined from the percent composition.

• Example: Lithium in Li3PO4: $17.98\%$

Yield Calculations

The percent yield is calculated by comparing the actual yield to the theoretical yield.

• Formula: $\%\text{yield} = \frac{\text{actual yield}}{\text{theoretical yield}} \times 100\%$

• Example: $\%\text{yield} = 22.5\%$

Classification and Identification

Types of Substances

• Molecular Elements: Elements that exist as molecules, e.g., O2, N2.

• Ionic Compounds: Compounds formed from cations and anions, e.g., KCl.

• Organic Compounds: Compounds containing carbon, such as ketones, alcohols, and carboxylic acids.

Functional Groups in Organic Chemistry

• Ketones: Organic compounds with a carbonyl group bonded to two carbon atoms.

• Alcohols: Organic compounds with a hydroxyl group (-OH).

• Carboxylic Acids: Organic compounds with a carboxyl group (-COOH).

Tables and Data Interpretation

Fractional Subcharges Table

This table provides conversion factors for fractional subcharges, useful for calculations involving ions and charge balancing.

Fractional Subcharge	Multiply by This
1/2	2
1/3	3
1/4	4
1/5	5
1/6	6
1/7	7
1/8	8
1/9	9
1/10	10

Sample Table: Mn Analysis Results

Sample	%Mn
1	0.533
2	0.615
3	0.526
4	0.549
5	0.540

Purpose: Used to calculate mean, median, and percent error in analytical chemistry.

Periodic Table of the Elements

The periodic table organizes elements by increasing atomic number and groups elements with similar chemical properties. It is essential for identifying element symbols, atomic numbers, and periodic trends.

Additional Info

• Some questions involve calculation of molar mass, empirical and molecular formulas, and percent yield, which are foundational skills in general chemistry.

• Students should be familiar with basic laboratory techniques, significant figures, and the use of conversion factors.