Chapter 2 HW
The element antimony (Sb) has an atomic mass of 121.76 amu. Two naturally occurring isotopes of antimony are 121Sb (57% abundant) and 123Sb (43% abundant). In a sample of 100 Sb atoms, what is the probability that a single selected atom has a mass of 121.76 amu?
0%. The atomic mass is an average that represents the abundance of each isotope. No individual atom has this mass.
Determine the number of protons (p) and electrons (e) in Mg²⁺.
12 p, 10 e Mg has an atomic number of 12, so it contains 12 protons. The neutral atom would have 12 electrons, but because the ion has a +2 charge, this indicates that there are two fewer electrons.
How many electrons are in a neutral 41Ca atom?
20. Calcium has 20 protons. Therefore a neutral calcium atom has 20 electrons.
An unknown element is a mixture of isotopes 120X and 122X. The average atomic mass of X is 120.48 amu. What is the percent abundance of 122X?
24% x = portion of 122X atoms 1-x = potion of 120X atoms 122(x) + 120(1-x) = 121.47 122x + 120 - 120x = 121.47 2x + 120 = 121.47 2x = 1.47 x = 0.735 73.5% or 74.0% 122X atoms 24.0% 120X atoms
How many protons (p) and electrons (e) are found in a Se²⁻ ion?
34 p, 36 e Se has an atomic number of 34, so it contains 34 protons. The neutral atom would have 34 electrons, but because the ion has a -2 charge, this indicates that there are two additional electrons.
An unknown element X has the following isotopes: 52X (91.00% abundant), 49X (8.00% abundant), 50X (1.00% abundant). What is the average atomic mass in amu of X?
51.7 amu (0.91 x 52) + (0.08 x 49) + (0.01 x 50) 47.32 + 3.92 + 0.5 51.74 = 51.7 amu
Determine the correct formula for aluminum oxide.
Al₂O₃ Aluminum ions = +3 charge Oxygen ions = -2 charge It would take 2 aluminum ions to balance out the 3 oxygen ions.
What is the formula of a compound containing Al³⁺ and S²⁻ ions?
Al₂S₃ Two aluminum ions are needed to balance out the negative charge on the three sulfur ions.
Which postulate(s) of Dalton's atomic theory of matter is/are NOT true?
Atoms of a given element are identical AND Atoms are indestructible.
Which has the incorrect name-formula combination? A) Cobalt(II) chlorite - Co(ClO₂)₂ B) Iron(II) chlorate - FeClO₄ C) Manganese(II) perchlorate - Mn(ClO4)₂ D) Chromium(III) hypochlorite - Cr(ClO)₃
B) Iron(II) chlorate - FeClO₄
Based on the positions of the following elements on the periodic table, which of them would you expect to form a 3+ cation? A) scandium B) aluminum C) phosphorus D) calcium E) Both A and B
Both A and B Scandium loses one 3d electron and two 4s electrons to form the Sc³⁺ cation. Aluminum loses one 3p electron and two 3s electrons to form the Al³⁺ cation.
hypobromite ion
BrO -
Which has the correct name-formula combination? A) Chlorine pentafluoride - CIF B) Diphosphorus pentoxide - P₂O C) Carbon tetraiodide - CI₄ D) Sulfur tetrafluoride - SF
C) Carbon tetraiodide - CI₄
Glucoe is an important biological molecule with the molecular formula C₆H₁₂O₆. What is its empirical formula?
CH₂O
What is the formula for cobalt(III) hydroxide?
Co(OH)₃ Cobalt(III) has a 3+ charge. Hydroxide is a polyatomic ion that has a -1 charge. Three hydroxide ions would be needed to balance the charge on the cobalt ion.
Methylene chloride (dichloromethane, CH₂Cl₂) was once a common ingredient in many paint strippers. Based on its molecular formula, what kind of bonding does this compound exhibit?
Covalent only Three nonmetals are present, therefore it has covalent bonds.
A molecule has an empirical formula of CH, and its molar mass is known to be 26 g/mol. What is its molecular formula?
C₂H₂ Carbon atom mass: 12.011 Hydrogen atom mass: 1.008 = 13 2 of each would give a molar mass of 26
Cathode rays are composted of what fundamental particle?
Electrons
sulfurous acid
H2SO3 (aq)
hydrobromic acid
HBr (aq)
hypobromous acid
HBrO (aq)
perchloric acid
HClO4 (aq)
A mass spectrometer measures neon to have two masses: 20 and 22 atomic mass units. These are:
Isotopes
Rutherford's gold foil experiment determined that...
Most of the space in an atom is empty except for a concentrated area called the nucleus.
Classify the following compounds as ionic or covalent: OF₂ CuO SeO₂
OF₂ is covalent. CuO is ionic. SeO₂ is covalent. Ionic bonds occur between a metal and a nonmetal. Covalent bonds occur between two nonmetals.
Which scientist determined the charge of the electron?
Robert Millikan
What does the mass number of an atom represent?
Total number of protons and neutrons in the atom
What is the correct IUPAC name for HC₂H₃O₂(aq)?
acetic acid
What is the correct IUPAC name for Al₂(SO₃)₃?
aluminum sulfite
NH4 +
ammonium ion
What is the correct IUPAC name for Ca(BrO₂)₂?
calcium bromite
What is the correct IUPAC name for CBr₄?
carbon tetrabromide
CO3 2-
carbonate ion
What is the correct IUPAC name for Cr₂O₃?
chromium(III) oxide
What is the correct IUPAC name for Cl₂O₇?
dichlorine heptoxide
What is the correct IUPAC name for HBrO(aq)?
hypobromous acid
What is the correct IUPAC name for Mg₃P₂?
magnesium phosphide
Bromine (Br) is NOT a...
metalloid Bromine is a main group nonmetal that is part of the halogen family.
What is the correct IUPAC name for HNO₃(aq)?
nitric acid
What is the correct IUPAC name for NI₃?
nitrogen triiodide
What is the correct IUPAC name for Ag₂S?
silver sulfide
What is the correct IUPAC name for Na₂SO₃?
sodium sulfite
