Chapter 2 Review Questions 30371a
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Michael Santostefano Mr. Werkheiser Chemistry – 5th period 1 November 2017 Chapter 2 Review Questions: 2.1-2.57 (odd) 2.1: Define the following : (a) ray, (b) ray, (c) ray, (d) X ray. (a) ray: a ray that is produced by the decay of radioactive substances that is consisted of positively charged particles (2 protons and 2 neutrons) and is attracted to a negatively-charged electric field. (b) ray: a ray that is produced by the decay of radioactive substances that is consisted of negatively charged particles (electrons) and is attracted to a positively-charged electric field. (c) ray: a high-energy ray that has no electric charge and is not attracted to any electric field. (d) X ray: a type of electromagnetic radiation that, not unlike radiation, is not affected by any external electric field. 2.3: Compare the properties of the following: particles, cathode rays, protons, neutrons, electrons. particles and protons are positively charged, cathode rays and electrons are negatively charged, and neutrons have no charge.
2.5: Describe the contributions of the following scientists to our knowledge of atomic structure: J. J. Thomson, R. A. Millikan, Ernest Rutherford, James Chadwick. J. J. Thomson: known for discovering the electron, cathode ray tube experiments, developing the formula to represent the ratio between an electron’s charge and its mass, and developing the the plum-pudding theory. Robert A. Millikan: known for resolving Thomson’s ratio, oil drop experiments, and discovering the numeric value of the mass and charge of an electron. Ernest Rutherford: known for discovering the nucleus of the atom, attempting to create a better model of the atom, and the gold foil experiments. James Chadwick: known for discovering and proving the existence of neutrons. 2.7: The diameter of a neutral helium atom is about 1 x 102 pm. Suppose that we could line up helium atoms side by side in with one another. Approximately how many atoms would it take to make the distance from end to end 1 cm? It would take approximately 10,000,000 helium atoms (or 1 x 107 helium atoms) to summate a total distance of 1 cm. T-G-M | k-h-dk-BASE-d-c-m | µ-n-p pico- to centi- = 10 decimal point movements to the left 1 x 102 pm = 100 pm = .00000001 cm = 1 x 10-8 cm 100 / .00000001 = 10,000,000 atoms = 1 x 107 atoms
2.9: Use the helium-4 isotope to define atomic number and mass number. Why does knowledge of atomic number enable us to deduce the number of electrons present in an atom? Helium-4: 42He Mass number: 4. The mass number (A) of an atom is the amount of protons and neutrons in a given atom or isotope. Atomic number: 2. The atomic number (Z) of an atom is the amount of protons in a given atom or isotope. Knowledge of atomic number enables us to deduce the number of electrons present in an atom because atomic number indicates the amount of protons in an atom, which will (in any neutral atom) equal the amount of electrons. 2.11: What do we call atoms of the same elements with different mass numbers? Atoms of the same element with different mass numbers are called isotopes. 2.13: What is the mass number of an iron atom that has 28 neutrons? An iron atom that has a neutron count of 28 has a mass number of 54. Neutrons = Mass number – atomic number 28 = A – 26 Mass number = 54 2.15: For each of the following species, determine the number of protons and the number of neutrons in the nucleus: 32He, 42He, 2412Mg, 2512Mg, 4822Ti, 7935Br, 19578Pt. 3He 2
has 2 protons and 1 neutron.
4He 2
has 2 protons and 2 neutrons.
24 Mg 12
has 12 protons and 12 neutrons.
25 Mg 12
has 12 protons and 13 neutrons.
48 Ti 22
has 22 protons and 26 neutrons.
79 Br 35
has 35 protons and 44 neutrons.
195 Pt 78
has 78 protons and 117 neutrons.
2.17: Write the appropriate symbol for each of the following isotopes: (a) Z = 11, A = 23; (b) Z = 28, A = 64. (a) 2311Na (sodium-23) (b)6428Ni (nickel-64) 2.19: What is the periodic table, and what is its significance in the study of chemistry? The periodic table is a chart in which elements of similar properties, chemical and physical, are grouped near each other. It is significant to chemistry because it correlates the properties of the elements systematically, which allows chemists to make predictions about chemical behavior. 2.21: Write the names and the symbols for four elements in each of the following categories: (a) nonmetal, (b) metal, (c) metalloid. (a) Carbon (C), fluorine (F), oxygen (O), and phosphorus (P) are nonmetals. (b) Copper (Cu), aluminum (Al), iron (Fe), and cium (Cd) are metals. (c) Astatine (As), boron (B), antimony (Sb), and germanium (Ge) are metalloids. 2.23: Elements whose names end with ium are usually metals; sodium is one example. Identify a nonmetal whose name ends with ium. Selenium is a nonmetal whose name ends with –ium.
2.25: Consult a handbook of chemical and physical data (ask your instructor where you can locate a copy of the handbook) to find (a) two metals less dense than water, (b) two metals denser than mercury, (c) the densest known solid metallic element, (d) the densest known solid nonmetallic element. (a) Sodium; density of 0.968 g/cm3. Potassium; density of 0.856 g/cm3. (b) Gold; density of 19.32 g/cm3. Iridium; density of 22.56 g/cm3. (c) The densest known solid metallic element is osmium; density of 22.61 g/cm 3. (d) The densest known solid nonmetallic element is iodine; density of 4.93 g/cm3.
2.27: What is the difference between an atom and a molecule? An atom is the smallest devisable amount possible of an element while a molecule is consisted of two or more atoms chemically bound together. 2.29: Describe the two commonly used molecular models. Ball-and-stick model: Atoms are represented by variously colored wooden or plastic balls with holes in them. Sticks are used to connect these balls, representing the chemical bonds between atoms. Space-filling model: Atoms are represented by balls that are held together by truncated fasteners, therefore the chemical bonds are unrepresented and invisible. The balls are proportional to the size of the actual atoms. 2.31: Which of the following diagrams represent diatomic molecules, polyatomic molecules, molecules that are not compounds, molecules that are compounds, or an elemental form of the compound? Diatomic molecules: (c)
Polyatomic molecules: (a) and (b) Molecules that are not compounds: (a) Elemental form of the compound: (a) 2.33: Identify the following as elements or compounds: NH3, N2, S8, NO, CO, CO2, H2, SO2. NH3: compound, N2: element, S8: element, NO: compound, CO: compound, CO2: compound, H2: element, SO2: compound. 2.35: Give the number of protons and electrons in each of the following common ions: K+, Mg2+, Fe3+, Br-, Mn2+, C4-, Cu2+. K+: 19 protons; 18 electrons Mg2+: 12 protons; 10 electrons Fe3+: 26 protons; 23 electrons Br-: 35 protons; 36 electrons Mn2+: 25 protons; 23 electrons C4-: 6 protons; 10 electrons Cu2+ 29 protons; 27 electrons 2.37: What does a chemical formula represent? What is the ratio of the atoms in the following molecular formulas? (a) NO, (b) NCl3, (c) N2O4, (d) P4O6. A chemical formula represents the composition of molecular and ionic compounds in of elemental structure by the usage of chemical symbols. (a) NO = 1:1 ratio (b) NCl3 = 1:3 ratio (c) N2O4 = 1:2 ratio
(d) P4O6 = 2:3 ratio 2.39: Give an example of a case in which two molecules have different molecular formulas but the same empirical formula. Glucose: C6H12O6; empirical formula: CH2O Formaldehyde: CH2O; empirical formula: CH2O 2.41: What is an ionic compound? How is electric neutrality maintained in an ionic compound? An ionic compound is a chemical compound that is formed of cations and anions. Electric neutrality is maintained in an ionic compound by ensuring that the charges from the cations and anions cancel each other out. 2.43: What are the empirical formulas of the following compounds? (a) C2N2, (b) C6H6, (c) C9H20, (d) P4O10, (e) B2H6. (a) CN (b) CH (c) C9H20 (d) P2O5 (e) BH3 2.45: Write the molecular formula of glycine, an amino acid present in proteins. The color codes are: black (carbon), blue (nitrogen), red (oxygen), and grey (hydrogen). Glycine: C2H5NO2 (how do I write this???) 2.47: Which of the following compounds are likely to be ionic? Which are likely to be molecular? SiCl4, LiF, BaCl2, B2H6, KCl, C2H4.
Ionic: LiF, BaCl2, KCl Molecular: SiCl4, B2H6, C2H4 2.49: What is the difference between inorganic compounds and organic compounds? Organic compounds contain carbon. All other compounds that do not include carbon are considered inorganic. 2.51: Give an example each for a binary compound and a ternary compound. Binary compound: aluminum oxide (Al2O3) Ternary compound: potassium hydroxide (KOH) 2.53: Explain why the formula HCl can represent two different chemical systems. The formula HCl can be used to represent the molecular compound hydrogen chloride as well as representing the chemical symbol for hydrochloric acid. 2.55: Naming the following compounds: (a) KH2PO4, (b) K2HPO4, (c) HBr (gas), (d) HBr (in water), (e) Li2CO3, (f) K2Cr2O7, (g) FeO, (h) Fe2O3, (i) TiCl4, (j) NaH, (k) Li3N, (l) Na2O, (m) Na2O2. (a) KH2PO4: potassium dihydrogen phosphate (b) K2HPO4: potassium hydrogen phosphate (c) HBr (gas): hydrogen bromide (d) HBr (in water): hydrobromic acid (e) Li2CO3: lithium carbonate (f) K2Cr2O7: potassium dichromate (g) FeO: iron (II) oxide (h) Fe2O3: iron (III) oxide
(i) TiCl4: titanium (IV) chloride (j) NaH: sodium hydride (k) Li3N: lithium nitride (l) Na2O: sodium oxide (m) Na2O2: sodium peroxide 2.57: Write the formulas for the following compounds: (a) rubidium nitrite, (b) potassium sulfide, (c) sodium hydrogen sulfide, (d) magnesium phosphate, (e) calcium hydrogen phosphate, (f) potassium dihydrogen phosphate, (g) iodine heptafluoride, (h) ammonium sulfate, (i) silver perchlorate, (j) boron trichloride. (a) Rubidium nitrite: RbNO2 (b) Potassium sulfide: K2S (c) Sodium hydrogen sulfide: NaHS (d) Magnesium phosphate: Mg3(PO4)2 (e) Calcium hydrogen phosphate: CaHPO4 (f) Potassium dihydrogen phosphate: KH2PO4 (g) Iodine heptafluoride: IF7 (h) Ammonium sulfate: (NH4)2SO4 (i) Silver perchlorate: NaClO4 (j) Boron trichloride: BCl3
2.5: Describe the contributions of the following scientists to our knowledge of atomic structure: J. J. Thomson, R. A. Millikan, Ernest Rutherford, James Chadwick. J. J. Thomson: known for discovering the electron, cathode ray tube experiments, developing the formula to represent the ratio between an electron’s charge and its mass, and developing the the plum-pudding theory. Robert A. Millikan: known for resolving Thomson’s ratio, oil drop experiments, and discovering the numeric value of the mass and charge of an electron. Ernest Rutherford: known for discovering the nucleus of the atom, attempting to create a better model of the atom, and the gold foil experiments. James Chadwick: known for discovering and proving the existence of neutrons. 2.7: The diameter of a neutral helium atom is about 1 x 102 pm. Suppose that we could line up helium atoms side by side in with one another. Approximately how many atoms would it take to make the distance from end to end 1 cm? It would take approximately 10,000,000 helium atoms (or 1 x 107 helium atoms) to summate a total distance of 1 cm. T-G-M | k-h-dk-BASE-d-c-m | µ-n-p pico- to centi- = 10 decimal point movements to the left 1 x 102 pm = 100 pm = .00000001 cm = 1 x 10-8 cm 100 / .00000001 = 10,000,000 atoms = 1 x 107 atoms
2.9: Use the helium-4 isotope to define atomic number and mass number. Why does knowledge of atomic number enable us to deduce the number of electrons present in an atom? Helium-4: 42He Mass number: 4. The mass number (A) of an atom is the amount of protons and neutrons in a given atom or isotope. Atomic number: 2. The atomic number (Z) of an atom is the amount of protons in a given atom or isotope. Knowledge of atomic number enables us to deduce the number of electrons present in an atom because atomic number indicates the amount of protons in an atom, which will (in any neutral atom) equal the amount of electrons. 2.11: What do we call atoms of the same elements with different mass numbers? Atoms of the same element with different mass numbers are called isotopes. 2.13: What is the mass number of an iron atom that has 28 neutrons? An iron atom that has a neutron count of 28 has a mass number of 54. Neutrons = Mass number – atomic number 28 = A – 26 Mass number = 54 2.15: For each of the following species, determine the number of protons and the number of neutrons in the nucleus: 32He, 42He, 2412Mg, 2512Mg, 4822Ti, 7935Br, 19578Pt. 3He 2
has 2 protons and 1 neutron.
4He 2
has 2 protons and 2 neutrons.
24 Mg 12
has 12 protons and 12 neutrons.
25 Mg 12
has 12 protons and 13 neutrons.
48 Ti 22
has 22 protons and 26 neutrons.
79 Br 35
has 35 protons and 44 neutrons.
195 Pt 78
has 78 protons and 117 neutrons.
2.17: Write the appropriate symbol for each of the following isotopes: (a) Z = 11, A = 23; (b) Z = 28, A = 64. (a) 2311Na (sodium-23) (b)6428Ni (nickel-64) 2.19: What is the periodic table, and what is its significance in the study of chemistry? The periodic table is a chart in which elements of similar properties, chemical and physical, are grouped near each other. It is significant to chemistry because it correlates the properties of the elements systematically, which allows chemists to make predictions about chemical behavior. 2.21: Write the names and the symbols for four elements in each of the following categories: (a) nonmetal, (b) metal, (c) metalloid. (a) Carbon (C), fluorine (F), oxygen (O), and phosphorus (P) are nonmetals. (b) Copper (Cu), aluminum (Al), iron (Fe), and cium (Cd) are metals. (c) Astatine (As), boron (B), antimony (Sb), and germanium (Ge) are metalloids. 2.23: Elements whose names end with ium are usually metals; sodium is one example. Identify a nonmetal whose name ends with ium. Selenium is a nonmetal whose name ends with –ium.
2.25: Consult a handbook of chemical and physical data (ask your instructor where you can locate a copy of the handbook) to find (a) two metals less dense than water, (b) two metals denser than mercury, (c) the densest known solid metallic element, (d) the densest known solid nonmetallic element. (a) Sodium; density of 0.968 g/cm3. Potassium; density of 0.856 g/cm3. (b) Gold; density of 19.32 g/cm3. Iridium; density of 22.56 g/cm3. (c) The densest known solid metallic element is osmium; density of 22.61 g/cm 3. (d) The densest known solid nonmetallic element is iodine; density of 4.93 g/cm3.
2.27: What is the difference between an atom and a molecule? An atom is the smallest devisable amount possible of an element while a molecule is consisted of two or more atoms chemically bound together. 2.29: Describe the two commonly used molecular models. Ball-and-stick model: Atoms are represented by variously colored wooden or plastic balls with holes in them. Sticks are used to connect these balls, representing the chemical bonds between atoms. Space-filling model: Atoms are represented by balls that are held together by truncated fasteners, therefore the chemical bonds are unrepresented and invisible. The balls are proportional to the size of the actual atoms. 2.31: Which of the following diagrams represent diatomic molecules, polyatomic molecules, molecules that are not compounds, molecules that are compounds, or an elemental form of the compound? Diatomic molecules: (c)
Polyatomic molecules: (a) and (b) Molecules that are not compounds: (a) Elemental form of the compound: (a) 2.33: Identify the following as elements or compounds: NH3, N2, S8, NO, CO, CO2, H2, SO2. NH3: compound, N2: element, S8: element, NO: compound, CO: compound, CO2: compound, H2: element, SO2: compound. 2.35: Give the number of protons and electrons in each of the following common ions: K+, Mg2+, Fe3+, Br-, Mn2+, C4-, Cu2+. K+: 19 protons; 18 electrons Mg2+: 12 protons; 10 electrons Fe3+: 26 protons; 23 electrons Br-: 35 protons; 36 electrons Mn2+: 25 protons; 23 electrons C4-: 6 protons; 10 electrons Cu2+ 29 protons; 27 electrons 2.37: What does a chemical formula represent? What is the ratio of the atoms in the following molecular formulas? (a) NO, (b) NCl3, (c) N2O4, (d) P4O6. A chemical formula represents the composition of molecular and ionic compounds in of elemental structure by the usage of chemical symbols. (a) NO = 1:1 ratio (b) NCl3 = 1:3 ratio (c) N2O4 = 1:2 ratio
(d) P4O6 = 2:3 ratio 2.39: Give an example of a case in which two molecules have different molecular formulas but the same empirical formula. Glucose: C6H12O6; empirical formula: CH2O Formaldehyde: CH2O; empirical formula: CH2O 2.41: What is an ionic compound? How is electric neutrality maintained in an ionic compound? An ionic compound is a chemical compound that is formed of cations and anions. Electric neutrality is maintained in an ionic compound by ensuring that the charges from the cations and anions cancel each other out. 2.43: What are the empirical formulas of the following compounds? (a) C2N2, (b) C6H6, (c) C9H20, (d) P4O10, (e) B2H6. (a) CN (b) CH (c) C9H20 (d) P2O5 (e) BH3 2.45: Write the molecular formula of glycine, an amino acid present in proteins. The color codes are: black (carbon), blue (nitrogen), red (oxygen), and grey (hydrogen). Glycine: C2H5NO2 (how do I write this???) 2.47: Which of the following compounds are likely to be ionic? Which are likely to be molecular? SiCl4, LiF, BaCl2, B2H6, KCl, C2H4.
Ionic: LiF, BaCl2, KCl Molecular: SiCl4, B2H6, C2H4 2.49: What is the difference between inorganic compounds and organic compounds? Organic compounds contain carbon. All other compounds that do not include carbon are considered inorganic. 2.51: Give an example each for a binary compound and a ternary compound. Binary compound: aluminum oxide (Al2O3) Ternary compound: potassium hydroxide (KOH) 2.53: Explain why the formula HCl can represent two different chemical systems. The formula HCl can be used to represent the molecular compound hydrogen chloride as well as representing the chemical symbol for hydrochloric acid. 2.55: Naming the following compounds: (a) KH2PO4, (b) K2HPO4, (c) HBr (gas), (d) HBr (in water), (e) Li2CO3, (f) K2Cr2O7, (g) FeO, (h) Fe2O3, (i) TiCl4, (j) NaH, (k) Li3N, (l) Na2O, (m) Na2O2. (a) KH2PO4: potassium dihydrogen phosphate (b) K2HPO4: potassium hydrogen phosphate (c) HBr (gas): hydrogen bromide (d) HBr (in water): hydrobromic acid (e) Li2CO3: lithium carbonate (f) K2Cr2O7: potassium dichromate (g) FeO: iron (II) oxide (h) Fe2O3: iron (III) oxide
(i) TiCl4: titanium (IV) chloride (j) NaH: sodium hydride (k) Li3N: lithium nitride (l) Na2O: sodium oxide (m) Na2O2: sodium peroxide 2.57: Write the formulas for the following compounds: (a) rubidium nitrite, (b) potassium sulfide, (c) sodium hydrogen sulfide, (d) magnesium phosphate, (e) calcium hydrogen phosphate, (f) potassium dihydrogen phosphate, (g) iodine heptafluoride, (h) ammonium sulfate, (i) silver perchlorate, (j) boron trichloride. (a) Rubidium nitrite: RbNO2 (b) Potassium sulfide: K2S (c) Sodium hydrogen sulfide: NaHS (d) Magnesium phosphate: Mg3(PO4)2 (e) Calcium hydrogen phosphate: CaHPO4 (f) Potassium dihydrogen phosphate: KH2PO4 (g) Iodine heptafluoride: IF7 (h) Ammonium sulfate: (NH4)2SO4 (i) Silver perchlorate: NaClO4 (j) Boron trichloride: BCl3
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