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Questions and Answers
What does a mass spectrum primarily display?
What does a mass spectrum primarily display?
If a mass spectrum shows three distinct peaks, what does this imply about the element being analyzed?
If a mass spectrum shows three distinct peaks, what does this imply about the element being analyzed?
In a mass spectrum, what does the height of each peak indicate?
In a mass spectrum, what does the height of each peak indicate?
If a mass spectrum displays two peaks, with one being taller than the other, what can be inferred?
If a mass spectrum displays two peaks, with one being taller than the other, what can be inferred?
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What primarily causes the differing horizontal positions of the peaks in a mass spectrum?
What primarily causes the differing horizontal positions of the peaks in a mass spectrum?
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What is the first step in determining the empirical formula of a compound given its percentage composition?
What is the first step in determining the empirical formula of a compound given its percentage composition?
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After converting percentages to masses, what is the next step in determining the empirical formula?
After converting percentages to masses, what is the next step in determining the empirical formula?
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Why are the mole amounts divided by the smallest mole amount in determining empirical formulas?
Why are the mole amounts divided by the smallest mole amount in determining empirical formulas?
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What is the significance of finding whole number ratios in the determination of empirical formulas?
What is the significance of finding whole number ratios in the determination of empirical formulas?
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In a sample, if after calculating the mole amounts and dividing by the smallest mole amount, you get 1.5 for a certain element, what should you do?
In a sample, if after calculating the mole amounts and dividing by the smallest mole amount, you get 1.5 for a certain element, what should you do?
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Study Notes
Significant Figures (Sig Figs)
- Non-zero digits are always significant
- Zeros between significant digits are significant
- Leading zeros are not significant
- Trailing zeros are significant if a decimal point is present
- Addition/Subtraction: Round the answer to the fewest decimal places
- Multiplication/Division: Round the answer to the fewest significant figures
Unit Conversions
- 1 mL = 0.001 L (Divide by 1000)
- 1 L = 1000 mL (Multiply by 1000)
- 1 g = 1000 mg (Multiply by 1000)
- 1 mg = 0.001 g (Divide by 1000)
- 1 km = 1000 m
- 1 m = 100 cm
- 1 cm = 10 mm
Atoms, Elements, and Compounds
- Atom: Smallest unit of an element that retains its properties
- Element: Pure substance made of one type of atom
- Compound: Substance made of two or more different elements chemically bonded
States of Matter
- Solid: Definite shape and volume; particles closely packed
- Liquid: Definite volume, takes shape of container; particles can move around
- Gas: No definite shape or volume; particles are far apart and move freely
Physical vs. Chemical Change
- Physical Change: Does not alter chemical composition (e.g., melting, freezing)
- Chemical Change: Results in the formation of new chemical substances (e.g., combustion, rusting)
Physical and Chemical Properties
- Physical Property: Observed or measured without changing the substance (e.g., color, melting point)
- Chemical Property: Describes a substance's ability to undergo a chemical change (e.g., flammability, reactivity)
Dalton's Atomic Theory
- All matter is made of atoms
- Atoms of the same element are identical
- Atoms combine in simple whole-number ratios to form compounds
- Chemical reactions involve the rearrangement of atoms
Atomic Models
- J.J. Thomson: Discovered the electron
- Ernest Rutherford: Discovered the nucleus
- Niels Bohr: Proposed that electrons orbit the nucleus in fixed paths (energy levels)
Structure of the Atom
- Protons: Positively charged, in the nucleus
- Neutrons: Neutral charge, in the nucleus
- Electrons: Negatively charged, outside the nucleus
Periodic Table
- Periodic: Repeating trends or patterns
- Elements are arranged by increasing atomic number
- Groups/Families: Vertical columns, similar chemical properties
- Periods: Horizontal rows, properties change gradually
Families on the Periodic Table
- Alkali Metals: Group 1, highly reactive
- Alkaline Earth Metals: Group 2, reactive
- Transition Metals: Groups 3-12, can have multiple charges
- Halogens: Group 17, highly reactive
- Noble Gases: Group 18, inert, non-reactive
Isotopes
- Isotopes: Atoms of the same element with different numbers of neutrons
Mass Spectrum
- Mass spectrum shows relative abundance of isotopes
- Used to identify the element
Naming Ionic Compounds
- Binary Ionic Compounds: Composed of two elements, name cation (metal) first, then anion (non-metal)
- Ternary Ionic Compounds: Contain a polyatomic ion, name cation first, then the polyatomic ion
- Ionic Compounds with Multiple Charges: Indicate the charge with Roman numerals
Empirical Formula
- Empirical formula: Simplest ratio of elements in a compound
Percent Composition
- Percent composition = (mass of element / molar mass of compound) x 100
Laws of Conservation in Chemical Reactions
- Law of Conservation of Mass: Mass is neither created nor destroyed in a chemical reaction
Kinetic Molecular Theory of Gases
- Gases are made of tiny particles in constant motion
- Gas particles are far apart, have negligible volume, and experience elastic collisions
- Avg. kinetic energy is directly proportional to temperature
Gas Laws
- Boyle's Law: Pressure and volume are inversely related (constant temperature)
- Charles's Law: Volume and temperature are directly related (constant pressure)
- Gay-Lussac's Law: Pressure and temperature are directly related (constant volume)
- Ideal Gas Law: PV = nRT (relates pressure, volume, temperature and moles)
- Dalton's Law of Partial Pressures: Ptotal = P1 + P2 + ...
- Graham's Law: Rate of effusion is inversely proportional to the square root of molar mass
Stoichiometry
- Mole-to-Mole Conversions: Use balanced chemical equations
- Limiting and Excess Reactants: Reactant that runs out first determines amount of product
- Percent Yield = (Actual Yield / Theoretical Yield) x 100
Sample Problem Types
- Empirical Formula: Determining the simplest ratio of elements in a compound
- Mole-to-Mole Conversions: Converting between moles of different substances using a balanced equation
- Limiting Reactant Problems: Determining the reactant that is used up first and the amount of product that can be made
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Description
Test your knowledge on significant figures, unit conversions, types of matter, and the basic building blocks of chemistry such as atoms, elements, and compounds. This quiz will cover essential calculations and definitions that are foundational to understanding chemistry.
