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This resource offers a thorough collection of questions and answers for chem 121, a first-year chemistry course. It addresses core concepts like physical and chemical changes, SI units, precision vs. accuracy, significant figures, and the factor label method. Topics include atomic structure, isotopes, percent abundance, the periodic table, ionic and molecular compounds, balanced equations, molar mass conversions, empirical and molecular formulas, limiting reactants, and theoretical/percent yields. Aqueous solutions, solubility, precipitates, and historical atomic models (e.g., plum pudding) are also covered. Key scientists like Boyle, Lavoisier, Dalton, Thomson, Millikan, Rutherford, and Becquerel are mentioned, providing a strong base for understanding chemistry principles and problem-solving. It's ideal for exam preparation and deepening understanding of introductory chemistry.
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What's the difference between a physical change and a chemical change? A physical change is only changing the state of the substance, whereas a chemical change will alter the substance completely. Ex: physical = water to ice chemical = iron to rust Name the SI base units: Length = meter Mass = kilograms Time = seconds Temperature = Kelvin Name the SI prefixes: Mono - 1 Di - 2 Tri - 3 Tetra - 4 Penta - 5 Hexa - 6 Hepta - 7
Octa - 8 Nona - 9 Deca - 10 What's the difference between precision and accuracy? Precision = the closeness of a set of values obtained Accuracy = the closeness of a measurement to its true value Describe significant figures What is the factor label method? How do you use the factor label method? (historical and modern theories of atomic structure, i.e. Plum Pudding Model) Given a specific isotope, explain how to find the following:
What are the charges of the main groups of ions on the periodic table? Refer to periodic table How do we name ionic and molecular compounds? Molecular: (examples of compounds, chemical formulas vs. name of compound) How can we distinguish between ionic compounds and molecular compounds? Molecular compounds are composed only of nonmentals, while ionic compounds are composed of a nonmetal and a metal or metal and metal. What does a balanced equation tell us about the reaction?
How do you convert moles to mass? How do you convert mass to number of atoms? How do convert number of atoms to moles? How do we obtain the molar mass from molecular formulas? And from the periodic table? What is an empirical formula? a formula giving the proportions of the elements present in a compound but not the actual numbers or arrangement of atoms. What's the difference between an empirical formula and a molecular formula? Molecular formulas tell you how many atoms of each element are in a compound, and empirical formulas tell you the simplest or most reduced ratio of elements in a compound. What is a limiting reactant (aka reagent)?
What is a precipitate? an insoluble solid that emerges from a liquid solution Plum Pudding Model In J.J. Thomson's model, the atom is composed of electrons surrounded by a soup of positive charge to balance the electrons' negative charges, like negatively charged "plums" surrounded by positively charged "pudding". The electrons were thought to be positioned throughout the atom in rotating rings. In this model the atom was also sometimes described to have a "cloud" of positive charge. When a neutral atom loses electrons, it becomes _______, and is called a _______. positive cation When a neutral atom gains electrons, it becomes ______ negative anion Greek Philosophers proposed all matter was composed of four fundamentals substance Fire, Earth, Water, Air
2000 years of alchemy Attempt to turn metals to gold Robert Boyle (1627-1691) Seen as the first "chemist" to perform truly quantitative experiments. *First scientist to have an actual study Known for Boyles law Boyle's Law A principle that describes the relationship between the pressure and volume of a gas at constant temperature Pressure of gas is inversely proportional to its volume Georg Stahl (1660-1734) described phlogiston as the basis for the ability of an item to burn Antonine Lavoisier (1743-1794) French chemist, explained the true nature of combustion. Like Boyle regarded measurement as essential operation of chemistry
Compounds contained whole numbers of atoms as Dalton suggested and that Avogadro's hypothesis was correct J.J. Thomson (1856-1940) identified the first subatomic particle, the electron, using cathode rays. First ever important experiment Plum Pudding Model J.J Thomsons model of an atom, in which he thought electrons were randomly distributed within a positively charged cloud Robert Millikan (1868-1953) -oil drop experiment -determined charge and mass of electron Antonie Henri Becquerel discovered radioactivity 3 types of radiation alpha ( 2+ ion ( mass 7300 x larger than the electron) , beta ( high speed electrons) , gamma ( high energy light)
Ernest Rutherford (1871-1937) He did the gold foil experiment (a lead tube surrounding a radioactive sample that sent energy into a piece of gold foil surrounded by an alpha particle detector) to determine that the 999/1000 electrons would go through the foil while 1/1000 would hit the wall (nucleus) and describes the nuclear atom which has a positive nucleus (1/10000 atomic volume). How many subatomic particles are there? 3, protons, neutrons, electrons Ionization -Process by which an atom or a molecule acquires a negative or positive charge by gaining or losing an electron to form ion
Groups/family, period mass spectrometry An accurate method for comparing the masses of atoms ( or molecules ) We measure molecules in a unit called Mole We use ______ mass to calculate the mass of 1 mole of an atom (e.g carbon) atomic We use _________ mass to calculate the mass of 1 mole of molecule (e.g CO2) molecular The formula of a compound represents the _______ numbers of the various types of atom present relative The formula of a compound represents the ______ number of the various types of atoms present relative
Emprical Formula The smallest whole-number ratio of the atoms present in the compound molecular formula the actual formula of a compound combustion analysis A common technique for analyzing compounds is to burn a known mass of compound and weigh the amounts of product made Compounds are generally represented with a chemical formula All chemical formulas convey a limited amount of information The study of the numerical relationship between chemical quantities in a chemical reaction is called Stoichiometry
a solution containing a large amount of solute concentration = amount of solute in a given amount of solution moles/volume molecular compounds do not dissociate in an aq solution Material that dissolves in water, which conducts electricity are called Electrolytes Material that dissolve in water, that will not conduct electricity are called non-electrolytes Electrolyte solutions all contain ions dissolved in water Hydration (POLAR solvent)
Forming a shell around the ion Ions move around independently Acids are molecular compounds that ionize when they dissolve in water Molecules are pulled apart by their attraction for the water When acids ionize they form? H+ cations and also anions Weak acids are weak electrolytes HF (aq) + H2O (l) ----> H3O+ (aq) + F- (aq Strong acids are
Insoluble substances, weak electrolytes, and nonelectrolytes are written in molecule form Solids, liquids, and gases are not dissolved Selective Percipitation Separating cations by precipitations them one at a time. Acid-Base reactions are also called neutralization reactions The H+ from the acid and the OH- from the base combine to form water The cation from the base combines with the anion from the acid to make Salt Atoms that lose electrons are being oxidized Atoms that gain electrons are being reduced
Gas molecules are constantly in motion and exert a force on their container Pressure = Force per unit area. If we could measure the total amount of force exerted by gas molecules hitting the entire surface at any one instant we would know the pressure the gas is exerting Gas flows from ____ pressure to ___ pressure. high to low We use ______ to measure the pressure of a gas barometer there were three laws discovered that associated scientist in determining the ideal gas law Boyle's law, Charles Law, Avogadro's law,
