Matter and Energy
Which scientist carried out the cathode ray tube experiment to demonstrate that atoms contained negatively-charged particles?
A.Rutherford
D.Dalton
B.Einstein
E.Thomson
C.Millikan
E!
J.J. Thomson used cathode ray tubes; he observed that the rays were attracted to positive ends of a magnet and pushed away from the negative end.
Atoms in the same period (row) on the periodic table have ________ numbers of valence electrons and _______ properties.
A.dissimilar, dissimilar
B.dissimilar, similar
C.similar, similar
D.similar, dissimilar
A!
On the periodic table the rows are organized from left to right (Row 1 = hydrogen, helium). Each successive element has one more valence electron. Elements next to each other may have some properties in common, but they differ drastically the further apart they are.
Electrons have properties similar to...
A.particles
B.waves
C.both waves and particles
D.neither waves nor particles
C!
Electrons were first discovered as particles (Thompson, Rutherford), but were later found to behave as waves (Planck, Bohr, Einstein). This is commonly referred to as wave-particle duality.
Which of the following best describes the element sodium?
A.alkaline earth
C.halogen
B.noble gas
D.alkali
D!
Sodium is in Group IA of the periodic table, and elements in this group are called alkali metals. Alkaline earth elements are those in Group IIA, halogens are those in Group VIIA, and noble gases are those in Group VIIIA.
Which set of data is the most precise?
A. 5.0m; 5.4 m; 5.2m
B. 4.2m; 4.0m; 3.9m
C. 4.9m; 4.9m; 5.0m
D. 6.1m; 6.1m; 5.2m
C!
Precision reflects how close a series of measurements are (i.e. the standard deviation). The closer they are, the more precise the data.
Which scientist carried out the gold foil experiment to demonstrate that the positive charge in an atom is concentrated in a tiny nucleus?
A.Rutherford
D.Dalton
B.Einstein
E.Thomson
C.Millikan
A!
Ernest Rutherford carried out his gold foil experiments to test the validity of Thomson’s “Plum Pudding Model”. His conclusion was based on the observation that although most alpha particles passed through the foil, a very small fraction were deflected.
Consider a neutral atom that forms an ion with the electron configuration of [Ne] 3s2 3p6. The neutral atom that forms this ion is ____ and it forms the ion by ___.
A.phosphorus, losing three electrons.
B.aluminum, gaining five electrons.
C.silicon, losing four electrons
D.sulfur, gaining two electrons
E.scandium, losing two electrons
D!
The given electron configuration corresponds to Argon (Z = 18). Several nearby elements can form ions with that electron configuration by either gaining or losing electrons. Their location on the periodic table determines this. Phosphorous gains three electrons (A), and aluminum loses three electrons (B). Silicon can lose four electrons, but its electron configuration then becomes that of neon rather than argon (C). Scandium can also lose two electrons, but after doing so, it still has one electron left in its 3d-orbital (E).
A microwave oven emits microwave radiation through food with a wavelength of 12 cm. What is the frequency of this radiation?
A.3.6 X 10^9 s^−1
B.3.6 X 10^7 s^−1
C.2.5 X 10^9 s^−1
D.2.5 X 10^7 s^−1
E.4.0 X 10^−8 s^−1
F.2.5 X 10^16 s^−1
C!
Wavelength and frequency are inversely proportional to each other, and they are related to the speed of light by the equation ln= c. This can be rearranged to solve for the frequency given the wavelength, and a unit conversion is required to get cm to m.
How many unpaired electrons does an atom of germanium, Ge, have in its ground state?
A.0
D.3
B.1
E.4
C.2
C!
Germanium(Z = 32) has the electron configuration [Ar] 4s2 3d10 4p2. The two electrons in the 4p orbital are unpaired.
How many atoms are contained in 7.2 mL of mercury, Hg, a liquid metal? The density of mercury is 13.56 g/mL.
A.2.2 X 10^22 atoms
B.2.9 X 10^23 atoms
C.0.49 atoms
D.0.036 atoms
E.8.1 X 10^−26atoms
B!
The given volume is multiplied by the density to convert to grams. Grams are then converted to moles using the average atomic mass. Finally, moles are converted to atoms using Avogadro’s number
Consider a given amount of water, as its temperature increases, its volume also increases. What statement is true?
A.The hotter water has a greater density than the cooler water.
B.The hotter water is the same density as the cooler water.
C.The hotter water has a lesser density than the cooler water.
D.More information is needed to answer this question.
D!
Density is measured in terms of mass per volume. Temperature has no effect on the mass, but if the volume increases with the temperature, the mass will be divided by a larger number. This will decrease the value of the density.
Arrange the elements carbon, neon, sodium, and silicon by increasing first ionization energy.
increasing IE1 →
A.Na < Si<C<Ne
B.C < Ne <Na<SiC.
C< Na < Si<Ne
D.Na<C<Ne<Si
E.Ne<Si<C<Na
A!
As a trend, ionization energy generally increases from left to right within a row of the periodic table. It also tends to increase from the bottom up within a group. These two trends suggest that of the elements listed, neon would have the highest ionization energy (B, D, E), and sodium would have the lowest ionization energy (C).
One mole of photons has an energy of 194 kJ. What is the wavelength of these photons?
A.617 nm
D.450 nm
B.835 nm
E.700 nm
C.385 nm
A!
Energy is related to wavelength by the equation 𝑬=𝒉𝒄𝝀. This equation can be rearranged to solve for wavelength, 𝝀=𝒉𝒄𝑬. The energy needs to be converted from kJ / mol to J / photon, and the wavelength will need to be converted to nanometers
For a given mass, which of each pair has the greater number of moles?
Pair I: Pd or Pt
Pair II: SO2 or CH4
A. Pd and SO2
C. Pd and CH4
B. Pt and SO2
D. Pt and CH4
C!
For the first pair, the atomic mass of palladium is 106.42 g/mol while that of platinum is 195.08 g / mol. Since platinum has the larger value the number of moles in a given mass would be smaller for platinum than for palladium (B, D). In the second pair, the formula mass of SO2is 64.06 g/mol while that of CH4is 16.04 g/mol. Similar to the first pair, SO2has the larger value which leads to a smaller number of moles (A).
Which of the following results in a thermal energy increase to the surroundings?
A. melting
B. condensation
C. sublimation
D. vaporization
B!
Thermal energy is transferred to the surroundings when a substance is cooled down. Melting (solid to liquid), sublimation (solid to gas), and vaporization (liquid to gas) all require an energy input from the surroundings. In condensation, a gas changes to a liquid. Since gases are higher in energy than liquids, the difference is transferred to the surroundings.
Consider the following elementsCaGeTiBrWhich has/have two unpaired electrons in their ground-state electron configuration?
A.Ge only
B.Ca and Br
C.Ti only
D.Ge and Ti
E.Ca only
D!
The electron configuration for calcium is [Ar] 4s2. Its two outer electrons are paired (B, E). The electron configuration for germanium is [Ar] 4s23d104p2. Its two outer electrons are not paired (C).The electron configuration for titanium is [Ar] 4s2 3d2. Its two outer electrons are not paired (A).
An electron in n= 4 absorbs a photon of Lambda=2.16 ́103nm and transitions to n= 7. What is the energy difference, ΔE, between the two levels?
A.9.20 X 10^–20J
B.9.20 X 10^–29J
C.9.20 X 10^–11J
D.1.43 X 10^–21J
E.4.77 X 10^–20J
A!
The energy absorbed can be calculated from the wavelength using the equation 𝑬=𝒉𝒄𝝀. The wavelength needs to be converted from nanometers to meters.
Antimony, with an average atomic mass of121.75amu, has two naturally occurring isotopes: Sb-121 (120.904 amu) and Sb-122 (122.904 amu). What is the natural abundance of the lighter of these two isotopes?
A.55.83 %
D.63.21 %
B.42.79 %
E.57.70 %
C.50.00%
E!
The more abundantisotope will have an atomic mass closer to the average atomic mass:Sb-121: 121.75 –120.904 = 0.846Sb-122: 122.904 –121.75 = 1.154
3Since the mass of Sb-121 is closer to the average atomic mass, it has a natural abundance > 50% (B, C). It’s a bit of trial and error with the remaining choices, but each percentage can be multiplied by the atomic mass of Sb-121 and added to the corresponding percentages (1 – %Sb-121) multiplied by the atomic mass of Sb-122:
If A: .5583(120.904) + .4417(122.904) = 121.7874
If D: .6321(120.904) + .3679(122.904) = 121.6398
If E: .5770(120.904) + .4230(122.904) = 121.75
Some substance occupies a volume of 5.83×10^6 cm^3. What would the volume be in m^3?
A. 5.83 × 104m3
D. 5.83 × 10^−12 m^3
B. 5.83 × 10^2 m^3
E. 5.83 m^3
C. 5.83 × 10^–4 m^3
E!
This is a unit conversion from cubic centimeters to cubic meters. The conversion factor is 1m = 100cm. Because the units are cubed, the conversion factor also needs to be cubed
As atomic theory has developed according to the available evidence from the time of Dalton, which principle has stayed the same over time?
A.Atoms are indivisible.
B.All atoms of an element are identical.
C.An atom is the smallest unit of an element that can be identified as that element.
D.All atoms have a nucleus that is a very small part of the total volume of the atom.
C!
Atoms were believed to be indivisible until the discovery of subatomic particles (A). All atoms of an element were also believed to be identical to one another until the discovery of isotopes (B). While it is now known that the nucleus is a small part of the atom overall, that was not known at the time of Dalton (D). The debate over the “Plum Pudding Model” went on for almost 20 years.
Which valence electrons of these four atoms, whose ground-state electron configurations are presented below, experience the greater effective nuclear charge Zeff?
A.1s2 2s2
B.1s2 2s2 2p1
C.1s2 2s2 2p2
D.1s2 2s2 2p3
D!
The electron configurations listed as choices all correspond to elements in the 2ndrow of the periodic table (beryllium, boron, carbon, and nitrogen, respectively). Within a row of the periodic table, the effective nuclear charge increases from left to right which causes atomic radius to decrease. This can be calculated using the equation Zeff= atomic number –inner electrons.
Rubidium has a threshold frequency of 5.5×10^14 s^-1. In separate experiments, green light (525 nm) and cyan light (495 nm) were shone onto the surface of rubidium. In which experiment, if any, was the photoelectric effect observed?
A.Neither the green light nor the cyan light induced the photoelectric effect.
B.Only the green light induced the photoelectric effect.
C.Only the cyan light induced the photoelectric effect.
D.Both the green light and the cyan light induced the photoelectric effect.
D!
The threshold frequency corresponds to the minimum amount of energy required for the photoelectric effect to be observed. All three values could be converted to energy, but that requires a bit of work. A more direct approach can be to convert the threshold frequency to wavelength and use the inversely proportional relationship between wavelength and energy to compare (longer wavelengths = lower energy).
A quantum of energy is the amount to be gained or lost when an electron moves from one energy level to another. Which statement is correct regarding an electronic transition from n = 1 to n = 3?
A.This is an absorption and it is endothermic.
B.This is an absorption and it is exothermic.
C.This is an emission and it is endothermic.
D.This is an emission and it is exothermic.
A!
The energy increases as the level increases. A transition from n = 1 to n = 3 thus marks an energy increase. The electron absorbs the energy, and the process is endothermic.
Magnesium phosphate has the chemical formula Mg3(PO4)2 and has a formula mass of 262.9 g/mol. How many moles of the element phosphorus are in 125 g Mg3(PO4)2? Provide a numerical answer reported to three significant figures.
0.951
Using the formula, one mole of this compound contains two moles of phosphorus. This gives the multiplier 1mol Mg3(PO4)2= 2mol phosphorus. Now the given mass can be used with the two multipliers