1.
Which of the following statements from Dalton’s atomic theory is no longer true, according to modern atomic theory?
Correct Answer
C. All atoms of a given element are identical.
Explanation
According to modern atomic theory, the statement "All atoms of a given element are identical" from Dalton's atomic theory is no longer true. Modern atomic theory recognizes that atoms of the same element can have different isotopes, which means they can have different numbers of neutrons. This variation in the number of neutrons leads to differences in atomic mass, but the atoms still have the same number of protons and electrons, maintaining their elemental identity.
2.
Which one of the following statements about atomic structure is false?
Correct Answer
D. The number of protons and neutrons is always the same in the neutral atom.
Explanation
The statement "The number of protons and neutrons is always the same in the neutral atom" is false because the number of neutrons can vary in an atom. The number of protons determines the atomic number and defines the element, while the number of neutrons can vary, resulting in different isotopes of the same element.
3.
The element rhenium (Re) exists as two stable isotopes and 18 unstable isotopes. Rhenium-185 has in its nucleus
Correct Answer
D. 75 protons, 110 neutrons.
Explanation
The element rhenium (Re) has an atomic number of 75, which corresponds to the number of protons in its nucleus. The atomic number determines the element's identity. The isotope mentioned, rhenium-185, has 110 neutrons in its nucleus. This can be calculated by subtracting the atomic number (75) from the mass number (185). Therefore, the correct answer is 75 protons, 110 neutrons.
4.
All of the following are true except:
Correct Answer
B. Ions are formed by changing the number of protons in an atom’s nucleus.
Explanation
Ions are formed by adding or removing electrons from a neutral atom, not by changing the number of protons in an atom's nucleus. Changing the number of protons would result in a different element altogether, not an ion.
5.
Which of the following are incorrectly paired?
Correct Answer
C. O, halogen
Explanation
The incorrect pairing in the given options is O, halogen. Oxygen (O) is not a halogen, but rather a nonmetal. Halogens are a group of elements that include fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).
6.
Which of the following is incorrectly named?
Correct Answer
E. NO3 -, nitrite ion
Explanation
The given answer, NO3 -, nitrite ion, is incorrectly named. The correct name for NO3 - is nitrate ion, not nitrite ion. Nitrite ion is represented as NO2 -.
7.
Write the names of the following compounds in order: (hint: use all lower case letters and capitals in parenthesis for roman numerals)
-
FeSO4
-
NaC2H3O2
-
KNO2
-
Ca(OH)2
-
NiCO3
Correct Answer
iron (II) sulfate
sodium acetate
potassium nitrite
calcium hydroxide
nickel (II) carbonate
Explanation
The given compounds are listed in order according to their names. The names of the compounds are written using all lower case letters and capital letters in parenthesis for the roman numerals. The compounds are: iron (II) sulfate, sodium acetate, potassium nitrite, calcium hydroxide, and nickel (II) carbonate.
8.
In a combustion reaction, 46.0g of ethanol reacts with 96.0g of oxygen to produce water and carbon dioxide. If 54.0g of water is produced, what mass of carbon dioxide is produced? Use proper sig figs. (hint: law of conservation of mass)
Correct Answer
88.0
Explanation
In a combustion reaction, ethanol reacts with oxygen to produce water and carbon dioxide. The balanced equation for this reaction is: C2H5OH + 3O2 → 2CO2 + 3H2O. According to the stoichiometry of the equation, for every 2 moles of CO2 produced, 3 moles of H2O are produced. Therefore, the ratio of the masses of CO2 to H2O produced is 2:3. Given that 54.0g of water is produced, we can use this ratio to calculate the mass of CO2 produced. (54.0g water) * (2g CO2 / 3g H2O) = 36.0g CO2. However, since we are asked to use proper sig figs, the answer should be rounded to three significant figures, which gives us 36.0g CO2.
9.
Identify the periodic groups associated with Alkali metals, Alkaline earth metals, Halogens, Noble gases and transition metals, in order. (use group numbers 1 through 18 and a series of groups with a dash, ex: 1-3)
Correct Answer
1
2
17
18
3-12
Explanation
The periodic groups associated with the given elements in order are group 1 (alkali metals), group 2 (alkaline earth metals), group 17 (halogens), group 18 (noble gases), and groups 3-12 (transition metals).
10.
Write the chemical formulas for the following compounds or ions, in order. Place subscripts, parenthesis, and charges where they are needed. Do not 'lower' the subscripts and leave a space between the ion and its charge. example: phosphate ion= PO4 3-, copper (II) nitrate = Cu(NO3)2, chloride ion = Cl -
-
nitrate ion
-
aluminum oxide
-
ammonium ion
-
perchloric acid
-
copper (II) bromide
Correct Answer
NO3 -
Al2O3
NH4 +
HClO4
CuBr2
Explanation
The chemical formulas for the given compounds or ions are as follows: nitrate ion (NO3 -), aluminum oxide (Al2O3), ammonium ion (NH4 +), perchloric acid (HClO4), copper (II) bromide (CuBr2).