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UT Arlington CHEM 1465 - Exam 1 Study Guide

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Chem 1465 1st EditionExam # 1 Study Guide Lectures: 1 - 6Lecture 1 (January 20)Chemistry introductionDescribe the three different perspectives of chemistry and the importance of each.Macroscopic is how we observe the world around us. In the macroscopic category- there is physical and chemical changes. Physical has no change in chemical ID while chemical does. Microscopic is all idea that all matter is composed of atoms and molecules. Atoms are the smallest particles, elements are the building blocks, and molecules are groups of atoms heldtogether. Symbolic is the last perspective and is what chemist use to represent atoms, molecules, and reactions.Precision versus accuracyDescribe the difference between precision and accuracy.Precision is how closely individual measurements agree with each other while accuracy is how closely measurements agree with an “accepted’ value.ErrorsDescribe the two different types of errors.Random errors are fundamental to measurements associated with the limitations of the instrument. For example a beaker versus a graduated cylinder. Systematic errors are consistently high or low of the accepted value and has an “unknown” bias. For example measuring a beaker without being at eye level.Know the SI unitsLecture 2 (January 22)Know the metric prefixesSignificant figuresWhat are the rules when deciding if a figure is significant? What rules do you follow when doingmultiplication and division as well as addition and subtraction? All nonzero digits are significant. A zero between two significant figures is significant. Leading zeros are not significant. Final zeros in a number with a decimal point aresignificant. Final zeros without a decimal point are ambiguous. When multiplying or dividing, use the number of significant figures that is least. When adding or subtracting, carry out the answer to the least precise significant figure. Atomic structureWhat is an ion? How are cations and anions different? What is an isotope? What is the atomic weight and how is it found?An ion is a charged particle, atoms, element, or molecules. In an ion the number of protons does not equal the number of electrons. Cations are positively charged ions while anions are negatively charged ions. Isotopes are atoms of the same element that differ only by number of neutrons. Atomic weight is the weighted average of the natural occurring isotopes. To find the atomic weight, you have to multiply the mass of the isotope by the percent abundance.Compounds and chemical bondsWhat is a chemical compound? What are the two types of chemical formulas? What are the three different types of chemical bonds?A chemical compound is two or more elements held together by chemical forces. A chemical formula shows the number and types of atoms. Molecular formula shows the exact number of elements while an empirical formula is a relative number of each element. The three different types of chemical bonds are ionic, metallic, and covalent bonds. In an ionic bond the metals lose an electrons to become a cation and the nonmetals gain an electron to become an anion. Metallic bonds are seas of electrons with delocalized sharing of electrons. Finally, covalent bonds are typically between two nonmetals sharing electrons. Lecture 3 (January 27)Chemical nomenclatureWhat is the difference between molecular compounds and ionic compound?In a molecular compound two nonmetal binary elements form a covalent bond. For these you use number prefixes. In ionic compounds one metal and one nonmetal binary compound forms an ionic bond. For these you do not use number prefixes. Know how to name cations and anions, as well as ionic compounds. Lecture 4 (January 29)Moles and molarityWhat is a mole? How do moles relate to mass? How do we get mole to mole ratios? What is molarity?A mole is the SI unit for the amount of substance something contains. A mole is a number word, similar to a dozen or a pound. A mole of a substance has molar mass that can be usedto convert back and forth from grams to moles. We can find mole to mole ratios from either the subscript of chemical formulas or from the coefficients of balanced equations. Molarity is 1 mole of solution divided into one liter. Lecture 5 (February 3)StoichiometryWhat must happen in a combustion reaction? What is a limiting reagent? What is the differencebetween actual yield, theoretical yield, and percent yield? In a combustion reaction, all carbon must be converted to CO2 and all hydrogen must be converted to H2O. When finding a limiting reagent, you are trying to decide which reactant is going to produce the least produce, based on how many grams of each reactant you have.Actual yield is the amount of product you collect at the end of a reaction. Theoretical yield isthe amount of product you predict you should get based on the limiting reagent. Finally, percent yield is the actual yield divided by the theoretical yield, then multiplied by


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