Chapter 3

Law of Conservation of Matter

  1. When 5g of compound A reacts with an unlimited amount of compound B, 7g of compound C is formed. How many grams of compound B must have reacted, and what law allows you to answer the question?

Law of Constant Composition

  1. Two different compounds, both consisting of sodium (Na) and oxygen (O), were analyzed. The data are given below:

Compound / Mass of Sample Analyzed / Mass of O Present / Mass of Na Present
A / 19.50 g / 8.00 g / ?
B / 61.98 g / 16.00 g / ?
  1. Fill in the last column of the table.
  2. Calculate the %Na and %O for both compounds.
  1. A 34.01-g sample of pure hydrogen peroxide produced at a chemical company contains 32.00 g of oxygen. The rest of the mass is due to hydrogen.
  1. What is the percent by mas of oxygen and hydrogen in this sample?
  1. Another company also produces pure hydrogen peroxide. What is the percent by mass hydrogen and oxygen in its hydrogen peroxide? What chemical law allowed you to answer this question?
  1. A 91.83-g sample of pure hydrogen peroxide is obtained. How many grams of it are oxygen?
  1. Tin, Sn, and oxygen can combine to form two different compounds called oxides. Oxide A contains 78.77% by mass tin. Oxide B contains 88.12% by mass tin. What is the percent by mass of oxygen in each oxide?

Define

  1. Dalton’s Atomic Theory:

Structure of the Atom

  1. Use Dalton’s hook atomic models to sketch a molecule of H2S.
  1. Complete the following statements:
  1. The nucleus contains the ______charged particles in the atom.
  2. The particles in the nucleus are the ______and ______.
  3. Almost all of the mass of an atom is contained in the ______.
  4. The two particles whose charges cancel to make an atom neutral are ______and ______.

Mass Number

  1. Fill in the following table for four neutral atoms:

158O
Mass Number / 16 / 37
Atomic Number / 8
Number of protons
Number of neutrons / 12
Number of electrons / 17 / 11
  1. How many protons, electrons, and neutrons are there in:
  1. 79Brp:e:n:
  2. 81Br-p:e:n:
  3. 23Na+p:e:n:
  4. 3H+p:e:n:

Weighted Average Atomic Mass / Isotopes

  1. Uranium exists mainly as two isotopes in nature, possessing mass numbers 235 and 238. Write the full atomic symbols for both isotopes.
  1. Give the full atomic symbol for the atom with 79e-, 79p, and 118n
  1. While an atom’s mass number and it’s atomic mass are not the same, they are often quite close to one another. Consider the following: Uranium-235 has an atomic mass of 235.043 93 amu and a percent abundance of 0.73%. Uranium-238 has an atomic mass of 238.0508 amu and a percent abundance of 99.27%. Without doing any calculations or consulting any other sources, which of the following do you think represents the atomic mass of naturally occurring uranium?
  2. 234.04 amu
  3. 236.03 amu
  4. 237.03 amu
  5. 238.03 amu
  6. 238.07 amu

Explain how you made your choice.

  1. The element nitrogen has only two naturally occurring isotopes: 107Ag with a mass of 106.90509 amu and an abundance of 51.84% and 109Ag with a mass of 108.9047 amu. Calculate the atomic mass of nitrogen.

Chemical Periodicity (Periodic Table)

  1. Complete the following statements:
  1. The elements in group IA are called ______.
  1. The elements in group IIA are called ______.
  1. The elements in group VIIA are called ______.
  1. The elements in group VIIIA are called ______.
  1. Use the elements lithium, potassium, and sodium to explain what is meant by chemical periodicity.
  1. Given that one measure of metallic character is the tendency to lose electrons, arrange Cs, Be, Li, Ne, Na in order of increasing metallic character.

Ionization Energy

  1. Fill in the following table:

158O+
Mass Number / 27 / 58
Atomic Number
Number of protons
Number of neutrons
Number of electrons
Charge on ion
  1. Of the atoms Na, Mg, and Al, which should be the most difficult to ionize? Which has the smallest first ionization energy?
  1. Of the atoms Na, Mg, and K, which should be the most difficult to ionize? Which has the smallest first ionization energy?
  1. Arrange Na, Cs, S, Cl in order of increasing first ionization energy.