Chem 11 - Exam #1 Sample

Sample Exams are designed to give you an idea of the types of questions you can expect.  Exam numbers may not exactly agree with currently assigned material, so you may need to examine other sample exams to see questions that might be similar to the upcoming exam. Answers for Sample Exam #1 are now available.

1. Please give the correct abbreviation for each of the following units of measurement. Then, express its numerical value in Liter, gram, or meter units.  For example: nanogram is abbreviated ng, and 1 ng = 10^-9 g.

• microliter
• millimeter
• kilogram
• centimeter
• deciliter
• picogram

2. Express 784,000,000 in exponential (scientific) notation. ___________________________

How many significant figures are there in the number 0.0006042? _______________________

3. The degree of agreement among several measurements of the same quantity is called __________________ and it reflects the reproducibility of a given type of measurement. The agreement of a particular value with the true value is called ______________________.

Substances with constant composition that can be broken down into elements by chemical processes are ___________________________. The state of matter for an object that has a definite volume but not a definite shape is _____________________. A pure substance can be either ____________________ or ____________________.

Give two examples that illustrate the law of multiple proportions: ________________ and _______________.

4. A sample of copper weighing 6.93 g contains how many moles of copper atoms? How many atoms?

5. A piece of indium with a mass of 16.6 g is submerged in a graduated cylinder containing 46.3 mL of water. After addition of this metal sample, the water level increases to 48.6 mL. What is the density of indium from these data? If the melting point of indium is 156.2^oC, what will be the physical state of indium at 323^oF?

6. Phosphoric acid can be prepared by reaction of sulfuric acid with "phosphate rock" according to the equation: Ca₃(PO₄)₂ + 3H₂SO₄ ---> 3CaSO₄ + 2H₃PO₄

What is the molar mass of Ca₃(PO₄)₂ ?

How many oxygen atoms are there in 1.55 ng of Ca₃(PO₄)₂ ?

Suppose the reaction is carried out starting with 103 g of Ca₃(PO₄)₂ and 75.0 g of H₂SO₄. Which reactant would be the limiting reactant?

7. A substance contains 35.0% nitrogen, 5.05% hydrogen, and 60.0% of oxygen. What is its empirical formula? How many grams of hydrogen are there in a 185-g sample of the substance?

8. Nitroglycerin is C₃H₅(NO₃)₃. Determine its percent composition (%C, %H, %N, %O). When nitroglycerin is used as an explosive (dynamite), it produces gaseous nitrogen, water, carbon dioxide and oxygen. Write a fully balanced equation for this reaction (it will take 3-4 passes to fully balance this equation). Then, based on this balanced equation, how many moles of nitrogen would be produced if you started with 100 grams of pure nitroglycerin?

9. Write the chemical formula for each of the following compounds or ions (ions must show the correct charge).

nitrate ion ____________________

aluminum oxide ____________________

ammonium ion ____________________

copper(II) bromide ____________________

aluminum hydroxide ____________________

hydrosulfuric acid ____________________

sulfurous acid ____________________

nitric acid ____________________

phosphoric acid ____________________

perchloric acid ____________________

potassium chromate ____________________

chromium(III) carbonate ____________________

dinitrogen pentoxide ____________________

copper(I) oxide ____________________

10. Write the correct name for each of the following compounds.

NH₄NO₃ __________________________

NaH __________________________

K₂Cr₂O₇ __________________________

CCl₄ __________________________

AgCl __________________________

CaS __________________________

HNO₂ __________________________

N₂O₃__________________________

SnI₂ __________________________

Al₂(SO₄)₃ __________________________

11. For each of the following, make the indicated conversions (show ALL work):

7.500 miles to kilometers (1 mile = 1.609 km):

-40.00 ^oC to ^oF:

68.00 ^oC to K:

12. For the following isotopes, give the atomic number (Z), number of protons, electrons, and neutrons present.

Isotope	Z	# protons	#electrons	#neutrons
45Ti
64Zn
72Ge
41K

___ T ___ F Atoms that have the same number of neutrons but different numbers of protons are called isotopes.

___ T ___ F The mass number of a nucleus represents the total number of protons in the nucleus.

Extra Credit (5 points)

Suppose that you lived in 1900 and discovered a new element and wanted to determine its atomic mass. You analyze a mass spectrum and find that there are two isotopes. One of the isotopes has an atomic mass of 20.011 and the other 22.015. The first isotope accounts for 35.00% of the total. What is the average atomic mass of this element as it occurs in nature?