Do all of you work on this exam. Use the back of the pages if needed. Do not use scrap paper. Do not erase; simply "x" out parts of answers you do not want graded. If the instructor cannot read your writing, then your answer will be counted wrong. All mathematical calculations must show the process of getting the answer on the test; answers without this will be counted wrong.
*** Express the calculated answer of each of the following in scientific notation and give the proper number of significant digits for each:
(a) 10.1 mol LiCl x (6.941 g Li/mol + 35.453 g Cl/mol Cl) = ??? (b) (27.4 cm x 14.6 cm x 1.0 cm) x 2.70 g/cm3 = ???
*** You want to calculate the density of a quarter (25¢). So you scrape up 37 coins. In the lab they weigh 207.286 g on the balance. To determine the volume you place water into a graduated cylinder and read the volume to be 52.2 mL. Then you drop all of the quarters into the water, and the volume now reads 75.4 mL. Show how to calculate the density of a quarter.
*** The density of sulfuric acid is 1.84 g/mL. What volume (in mL) should be taken to get 25.0 g of sulfuric acid?
*** The distance to the sun is 93,000,000 miles. Write this in scientific notation assuming:
Two significant digits. Three significant digits.
*** How many significant figures are there in each of the following:(a) 7008, (b) 0.00000625, (c) 3.400
*** Do the following calculations and express the answers with the correct number of significant figures:
(a) 6.25 x 7.5 = (b) 1.575 + 123.4 + 16.25 = (c) 8.27(4.987 - 4.962) = (d) (9.04 - 8.23 + 21.954 + 81.0)/3.1416 =
*** Define the following chemical terms: substance; molecular formula; homogeneous mixture; mixture, decompose
*** Give accurate definitions of the following chemical terms:
(a) element (b) molecule (c) intensive property (d) metalloid (e) allotrope
*** Briefly describe the similarities and differences between each of the following terms:
(a) precision and accuracy, (b) empirical formula and molecular formula, (c) theory and scientific law
*** Classify glue as an element, compound, or mixture. Give the characteristics of the category you choose and the observable properties of the glue which make it fit the category chosen.
*** Classify each of the following as either a compound, homogeneous mixture or heterogeneous mixture:
(a) sucrose and sand, (b) a 5% NaCl solution, (c) granite, (d) carbon dioxide, (e) oil and vinegar salad dressing
*** Suppose you were a chemistry student in the mid 1800’s (after John Dalton), and were asked to draw a picture (model) of atoms of hydrogen and oxygen. Show what you would do.
*** On the basis of information in Chapters 1 and 2, explain how your current model of hydrogen and oxygen atoms would be different now (2001) compared to the mid 1800’s.
*** Draw a microscopic picture, which represents an element in the gaseous state. Also draw a microscopic picture, which represents a mixture of 2 compounds and an element. Carefully explain the meaning of any symbols that you use.
*** In the following pictures, circles represent atoms. Label each picture as: element, compound, mixture of elements, mixture of compounds, mixture of element(s) and compound(s). It is possible that all choices will not be used and that a choice might be used more than once.
*** Critique the following: Any difference in properties of 2 substances can serve as a basis for a way to separate the substances in order to find the mass of each.
*** Complete the following chart:
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*** Give the symbol for an atom containing 60 electrons, 63 protons, and 88 neutrons.
*** What is the symbol of the microscopic particle with one nucleus, 10 protons, and 9 electrons?
*** How many electrons and protons would be expected in the cation of atomic number 38?
*** Most every periodic chart gives at least three basic pieces of information for each element. (This is true for the chart on the wall in LA 414.) Explain what the interger value and the letter(s) mean, and how they are used.
*** Using the new numbering system, which group contains element 32 in the periodic chart? Which period?
*** There are eight elements surrounding element 32 in the periodic chart. Tell whether each is a metal, nonmetal, or metalloid.
*** Elements 114, 116, and 118 were discovered for the first time in the summer of 1999. Tell where each should fit into the current periodic chart.
*** Which seven elements exist as diatomic molecules in nature?
*** At room temperature, which elements are (a) liquids, (b) gases?
*** Give the symbol of (a) an alkali metal, (b) a selenide ion
*** Tell what elements are in the same group as Sn
*** Which element(s) is(are) nonmetal(s) in the same period as Sn?
*** What is the name of the group of elements which normally form 1- ions?
*** Give correct symbols for each of the following elements: sodium , silver, copper, potassium, chlorine
*** Name these molecules:
(a) As2S3 (b) OsO4 (c) Pb3(PO4)2 (d) Co2(SO4)3 (e) NO2 (f) NF3 (g) Cr(CN)2
(h) NH4NO3 (i) K3PO4 (j) FeCl3 (k) CaSO4 (l) NaNO2
*** Write formulas for the following:
(a) ammonium carbonate (b) tin(IV) sulfate (c) calcium acetate dihydrate
(d) magnesium bromide (e) strontium acetate (f) phosphorus trichloride
*** Epsom salts consists of magnesium sulfate heptahydrate. (a) Write its formula.
*** The density of bismuth is 8.90 g/cm3. Calculate the volume (in liters, L) of 2.55 kg of bismuth.
*** The world record in the men’s 100 meter dash is 9.79 s. What is the corresponding average speed in km/hr?
*** A rectangle has an area of 4.8 in2. What is its area in mm2?