chem 1a final
Which diatomic molecule has the largest dipole moment?
A dipole moment occurs due to difference in electronegativity between the bonded atoms. Greater differences in electronegativity lead to a larger dipole moment. In this case, the differences in electronegativity values between hydrogen and fluorine is the greatest. Therefore, HF will have the largest dipole moment.
difference between molar mass and formula weight?
A formula weight is the mass of one molecule or formula unit while a molar mass is the mass of one mole of molecules or formula units.
Which of the following atoms is paramagnetic?
Al A paramagnetic ion/element is one whose electron configuration contains any unpaired electrons. Of the options given, only Al (electron configuration [Ne]3s²3p¹) has a single unpaired electron (the one electron in the 3p orbital), meaning it is paramagnetic.
Based on their positions in the periodic table, which of the following bonds is the most polar?
B-F Polar bonds occur between two nonmetals and have a difference in electronegativities of the atoms.The further apart two atoms are in the same period, the greater the polarity of the bond.
Einstein's work on the photoelectric effect validated and made extensive use of which of the following equations?
E = hν Einstein's achievements with the photoelectric effect proved that photons of sufficient energy were necessary to remove electrons from metal upon which they were shone. As a result, he made extensive use of the equation E = hν, which quantifies the energy (E) of a photon based on its frequency (ν) and Planck's constant (h)
electronegativity in atoms?
Electronegativity is the attraction an element's nucleus has for the electrons in a chemical bond.
Which of the following has an heat of formation equaling zero?
F2 Elements that are in their natural state have an enthalpy of formation that is equal to zero. F₂ is the only element on the list that is in its natural state. The others are diatomic molecules in their natural state.
Halogens tend to form anions because
Halogens tend to form anions because gaining electrons will fill their octet faster than losing them.
heat is what type of energy
Heat measures the total molecular motion of a substance, and is therefore a form of kinetic energy
All of these are factors that affect the effective nuclear charge, Zeff, EXCEPTlence electrons
MASS # The Zeff is affected by the type of orbital an electron occupies, the number of core electrons, and the number of valence electrons.
Which of the following pairs of ions represent isoelectronic species?
Mg²⁺ and O²⁻ Isoelectronic species are elements/ions with the same electron configuration (and therefore the same number of electrons). Of the options given, the species Mg²⁺ and O²⁻ both have the electron configuration of Ne (1s²2s²2p⁶), meaning they are isoelectronic.
Which of the following elements is the most electropositive?
Phosphorus is the least electronegative of this group and therefore the most electropositive.
Rank the following atoms in order of increasing first ionization energies (i.e., lowest to highest): Rb, F, Mg, B, N.
Rb < Mg < B < N < F In general, first ionization energy decreases down a group and increases across a period.
Based on the law of conservation of energy, the ___ of potential and kinetic energy is constant.
SUM For example, a ball on a track has only potential energy before it starts rolling, and an equivalent amount of kinetic translational and rotational energy at the bottom of the track.
What type of light on the electromagnetic spectrum has the highest energy per photon?
Since gamma waves have the highest frequency and shortest wavelength, they have the highest energy.
Most early attempts to organize the elements were based on atomic mass. Mendeleev occasionally switched elements so that apparently lighter elements occurred after a heavier element. He did this so that elemental properties properly recurred in the same group. This choice anticipated the discovery of which two features of elements?
The atomic number and isotopes of elements account for the switching of elements so that the lighter elements occured after a heavier element.
A bond dissociation energy is
The energy required to break a covalent bond.
In the photoelectric effect, if the intensity of light shone on a metal increases, what will happen?
There will be more electrons ejected Each photon is capable of ejecting one electron from the metal. Therefore, increasing the intensity of the light (the number of photons shone on the metal) will increase the number of electrons ejected from the metal
FERMINTATION
chemical change
Energy of a photon is ______ proportional to frequency, and _______ proportional to wavelength.
directly, inversely
ionic bonds are between
metals and nonmetals
A lattice energy is
the amount of energy that must be supplied to break an ionic solid into its individual gaseous ions
How many unpaired electrons are found in a ground state atom of O?
the electron configuration of O has four electrons in its p orbital, a p orbital can hold 6 max electrons in 3 sub orbitals, and hund's rules states each of those sub orbitals will have one electron before being paired with another electron.
In a covalent bond
two atoms share valence electrons and those shared electrons form the chemical bond.
Water is a polar molecule because
water is a bent molecule and oxygen is more electronegative than hydrogen.
Which of the following is true concerning ψ²?
ψ² describes the probability of finding an electron in space.
If a reaction is exothermic, what is true of its reverse reaction?
∆H > 0 The reverse reaction would be endothermic, which would have a positive ∆H.
Excited hydrogen atoms emit radiation in which region(s) of the electromagnetic spectrum?
Excited hydrogen atoms are capable of emitting radiation with wavelengths from 100 nm to 10,000 nm; this section of the electromagnetic spectrum includes IR, visible, and UV radiation.
Significat figures matter bc
-they provide most accurate number/answer -reflect the uncertainty in a measurement and precision of our measurements
-A single bond is longer than double bond -strongest bond is triple bond -shortest bond is triple bond
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Einstein's Theory of Relativity: falsifiable, makes predictions that can be tested by experiment, scientifically acceptable general principle, can be used as model to explain natural phenomena
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The accepted value for the density of iron is 7.9 g/mL. Which of the following sets of experimental data for the density of iron is the most accurate? Group 1: 7.98, 7.85g/ml
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The law of multiple proportions is used to explain how compounds, in this question, carbon monoxide and carbon dioxide, form by the combination of proportionate amounts of one element (oxygen) with a fixed amount of another (carbon).
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an exact number has no uncertainty
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An exothermic reaction causes the surroundings to
An exothermic reaction transfers energy from the system to the surroundings. That tells us the surroundings will get warmer.
Which one of the following processes is endothermic?
BOILING A LIQUID An endothermic process requires heat. Freezing a solid, condensation of a gas into a liquid, and condensation of a gas into a solid all release heat. Gases have more energy than liquids. For a liquid to become a gas, energy would be need to be added to the system.
Which of the following best explains why helium and neon do not form compounds whereas xenon and krypton can?
Larger noble gases like krypton and xenon have easier access to higher energy orbitals allowing them to expand their octets and form new bonds.
Which one of the following is the correct dissociation equation for Li₂CO₃?
Li₂CO₃ (s) → 2 Li⁺(aq) + CO₃²⁻ (aq) Lithium forms ions with a +1 charge. There are two lithium ions for every one carbonate ion. Carbonate has a -2 charge
Which of the following metals would be expected to have the smallest atomic radius?
The atomic radius increases as you move down the periodic table and to the left. Tantalum is the furthest to the right of this list and nearer the top and it would be expected to have the smallest atomic radius.
The energy released in the reaction F(g) + e⁻ → F⁻(g) is known as the
The electron affinity is the change in energy when an electron is added to a neutral gaseous atom to form an ion.
The ions formed when MgI₂ dissociates in water are
into Mg²⁺ and I⁻. The charges on the atoms can be determined by the number of electrons in their valence shells. Magnesium, Mg, is in Group 2 and loses 2 valence electrons to have a +2 charge. Iodine, I, is in Group 17 and has 7 valence electrons. Iodine will gain an electron to have take on a -1 charge.
A white powder mixture is placed into water. Some of the powder sinks to the bottom of the container, some rises to the top. The separation of the powder mixture is an example of
physical change
Which of the following metals would react most vigorously with water? A) Li B) Na C) K D) Rb
rb Reactivity for group 1 and group 2 metals generally increases as you move down the periodic table and to the left. Rubidium is the furthest down and to the left of this list, so it is expected to react the most vigorously with water.
Which types of electrons penetrates most toward the nucleus and therefore has the greatest shielding effect?
the s electrons penetrate most toward the nucleus and therefore have the greatest shielding effect.