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ALEKS Chemistry Answers Key
Yes, we will be discussing all ALEKS basic and intermediate chemistry-related topics including all previously asked questions.
Q. Matter
Ans: Anything that has mass and takes up space; made of atoms
Q. Atoms
Ans: The basic unit of matter which cannot be broken down and contain mostly empty space; contains three parts: the electron, proton, and neutron
Q. Elements
Ans: A pure substance that contains only one type of atom
Q. Compound
Ans: Two or more elements that are chemically bonded; includes ionic and covalent
Q. Mixture
Ans: Two or more substances that are together but not bonded
Q. Pure Substance
Ans: A substance that contains only one kind of compound
Q. Bose-Einstein Condensate
Ans: The state of matter with the lowest energy; is basically a very cold solid
Q. Solid
Ans: A state of matter with strong bonds
Q. Liquid
Ans: A state of matter with weak bonds
Q. Gas
Ans: A state of matter with no bonds
Q. Plasma
Ans: The state of matter with the highest energy; it uses ionization instead of bonds
Q. Robert Boyle
Ans: First to define an element; any substance is a substance unless it can be broken down
Q. John Dalton
Ans: Used and combined previous ideas to discuss the atom; elements are made of atoms; all atoms of an element are identical; atoms of different elements are different; law of constant composition; atoms are invisible
Q. Law of Constant Composition
Ans: Atoms of one element can combine with other elements to form compounds; a given compound always has the same relative numbers and types of atoms
Q. J.J. Thomson
Ans: Discovered electrons and protons and developed the plum pudding model of an atom
Q. Electrons
Ans: The negatively charged particle in an atom; circles around the nucleus in the electron cloud
Q. Proton
Ans: The positively charged particle in an atom; located in the nucleus; determine the element
Q. Neutron
Ans: The neutral particle in an atom; it has no charge and is located in the nucleus
Q. Plum Pudding Model
Ans: A model of the atom that depicts a sphere of positive charge with electrons scattered throughout
Q. Ernest Rutherford
Ans: Conducted an experiment in which he shot alpha particles at gold foil; roved there was a small, dense nucleus with a positive charge and that protons are positive
Q. Metals
Ans: Elements located on the left side of the periodic table that want to lose electrons
Q. Characteristics of Metals
Ans:
– Malleable
– Ductile
– Conductive
– Lustrous
Q. Malleable
Ans: The ability to be molded into shapes
Q. Ductile
Ans: The ability to be pulled into wire
Q. Conductive
Ans: The ability to allow heat or electricity to pass through an object
Q. Lustrous
Ans: The ability to be shiny
Q. Nonmetals
Ans: Elements located on the right side of the periodic table that want to gain electrons
Q. Metalloids
Ans: Elements placed in a stair-step line between metals and nonmetals; they have characteristics of both
Q. Diatomic Molecules
Ans: Elements that occur in pairs in their natural state; hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, iodine
Q. Electronegativity
Ans: The ability of a molecule to attract electrons to it; increases as you move left to right in the table and decreases as you move top to bottom; fluorine is the hardest
Q. Atomic Radius
Ans: The radius of an atom; decreases as you move left to right and increases as you move top to bottom
Q. Ionization Energy
Ans: The energy needed to rip off an electron; increases as you move left to right and decreases as you move top to bottom
Q. Ion
Ans: An atom that has gained or lost electrons
Q. Anion
Ans: An atom that gains electrons and has a negative charge; nonmetals
Q. Cation
Ans: An atom that loses electrons and has a positive charge; metals
Q. Isotope
Ans: An atom that has changed its number of neutrons
Q. Atomic Number
Ans: A unique number to each element that tells the number of protons and the number of electrons if the atom is neutral
Q. Atomic Mass
Ans: A number that tells the number of protons and neutrons in an atom
Q. Neutron Number
Ans: Atomic Mass – Atomic Number
Q. Radioactive
Ans: A nucleus that spontaneously decomposes, forming a different nucleus and producing one or more particles; alpha, beta, and gamma-ray
Q. Alpha Particle
Ans: One type of radioactive particle; is essentially a helium nucleus; when this type of particle is released, the mass of the atom is conserved and so is the atomic number
Q. Beta Particle
Ans: One type of radioactive particle; it is essentially an electron; when this type of particle is released, the atomic mass is conserved and the atomic number gains one (a neutron is changed to a proton)
Q. Gamma Ray
Ans: One type of radioactive particle; it is a high energy photon of light and is used to release excess energy; the atom is not changed at all
Q. Half-Life
Ans: The time required for half of the original sample of nuclei to decay; each radioactive nucleus of the same element has the same half-life; the shorter the half-life, the more likely a nucleus will decay
Q. Percent Abundance
Ans: Elements exist naturally in different isotopes, to the atomic mass listed on the table is an average
Q. Percent Abundance Equation
Ans: Average Mass = (%)•(Mass of Isotope A) + (%)•(Mass of Isotope B) +…
Q. Crest
Ans: The highest point of a wave
Q. Trough
Ans: The lowest point of a wave
Q. Wavelength
Ans: The distance between the crests of a wave; symbol is lambda
Q. Frequency
Ans: The number of waves that pass through a point in a given time; symbol is nu
Q. Amplitude
Ans: The height of a crest or trough; crest to the zero line; absolute value
Q. Speed
Ans: How fast a wave travels in a given distance
Q. Node
Ans: Point on a wave where the wave returns to the zero line; a crest or trough is trapped between the two points
Q. Electromagnetic Spectrum
Ans: The range of wavelengths or frequencies over which electromagnetic radiation extend
Q. Visible Light
Ans: White light is passed through a prism and creates all visible colors; each color has its own frequency and wavelength
Q. Atoms and Colors
Ans: When an atom is excited by the energy it gives off its own characteristic colors of light
Q. Photon
Ans: A light particle
Q. Speed of Light Equation
Ans:
C = w•f
C is the speed of light
w is wavelength in meters
f is frequency in hertz
Q. Speed of Light
Ans: 3.00•10^8m/s
Q. Continuous Spectrum
Ans: Broken bands of colored light
Q. Bright Line Spectrum
Ans: a.k.a. emission spectrum; occurs due to the energy an electron gives off as it travels from high to low energy; fireworks
Q. Dark Line Spectrum
Ans: a.k.a. absorption spectrum; occurs due to the energy that an electron gains as it travels from low to high energy
Q. Energy using Planck’s Constant
Ans:
E = h•f
E is energy
h is Planck’s constant
f is frequency in hertz
Q. Planck’s Constant
Ans: 6.626•10^-34 Joules/hertz
Q. Wave-Particle Duality of Light
Ans: Light sometimes acts like a particle and sometimes like a wave
Q. Wave-Mechanical Model of the Atom
Ans: A model of the atom in which the orbitals are nothing like orbits
Q. Heisenberg Uncertainty Principle
Ans: It is impossible to know the exact position and momentum of an electron at the same time
Q. Quantum Theory for an Atom
Ans: The probability of finding electrons in certain regions of an atom is described by orbitals
Q. Atomic Orbital
Ans: A region around the nucleus of an atom where an electron with a given energy may be found 90% of the time; 4 types: s, p, d, and f
Q. N
Ans: The principal quantum number; tells us which energy level an electron is found in, the maximum number of electrons that can be found in one energy level, and the size of an electron cloud
Q. L
Ans: The orbital quantum number; tells us the shape of the orbital (s,p,d,f)
Q. M
Ans: Quantum number that tells us the orientation of the orbital in space
Q. S
Ans: Quantum number that tells how an electron spins in an orbital
Q. Pauli Exclusion Principle
Ans: A rule that states that each electron has its own unique set of quantum numbers and that two electrons with the same spin cannot occupy the same orbital and that an orbital can only hold two electrons
Q. S Orbital
Ans: The orbital with the lowest energy; it has one orbital and can hold two electrons
Q. P Orbital
Ans: The orbital with the second-lowest energy; it has three orbitals and can hold six electrons
Q. D Orbital
Ans: The orbital with the second highest energy; it has five orbitals and can hold ten electrons
Q. F Orbital
Ans: The orbital with the highest energy; it has seven orbitals and can hold 14 electrons
Q. Hund’s Rule
Ans: Each suborbital will fill with one electron before accepting a second electron
Q. Valence Electrons
Ans: Electrons on outermost orbital; always the highest energy ‘s’ and ‘p’ orbital
Q. Oxidation State
Ans: The electrons an element will gain or lose in order to become stable (8 electrons)
Q. Acids
Ans: Always start with hydrogen; donate a proton in a solution
Q. Oxyacid
Ans: An acid that has an oxygen
Q. Organic Acid
Ans: An acid that contains a carbon atom
Q. Diprotic Acid
Ans: An acid that has 2 hydrogens to donate
Q. Tricrotic Acid
Ans: An acid that has 3 hydrogens to give
Q. Alcohols
Ans: Subtract a hydrogen and add a -OH group; add ol to end of name
Q. Ionic Bonds
Ans: The metal loses the electron and nonmetal gains it; the farther apart they are on the table the more likely it’s ionic
Q. Covalent Bonds
Ans: Atoms are sharing electrons; the closer the elements are the more likely it’s covalent
Q. Polar Covalent Bonding
Ans: Bond where electrons are shared unequally
Q. Lewis Structures
Ans: Represent the valence electrons
Q. Hydrogen Bonding
Ans: Occurs between hydrogen and F, N, or O
Q. IMF Scale
Ans: Dispersion < Dipoles < Hydrogen
Q. Molar Mass
Ans: Found by summing the masses of the component atoms
Q. Combination Reaction
Ans: Two or more compounds form to make one compound.
Q. Decomposition Reaction
Ans: A complex molecule breaks down to make a simpler one.
Q. Precipitation Reaction
Ans: Two solutions of soluble salts are mixed, resulting in an insoluble solid (precipitate) forming.
Q. Neutralisation Reaction
Ans: An acid and a base react with each other. Generally, the product of this reaction is salt and water.
Q. Combustion Reaction
Ans: Oxygen combines with a compound to form carbon dioxide and water. These reactions are exothermic, meaning they give off heat.
Q. Displacement Reaction
Ans: One element trades places with another element in the compound.
Q. Element
Ans: Any substance that contains only one kind of an atom
Q. Compound
Ans: Elements combine to form chemical compounds
Q. Ionic Compound
Ans: Metals often react with nonmetals to form ionic compounds. These compounds are composed of positive and negative ions formed by adding or subtracting electrons from neutral atoms and molecules.
Q. Covalent Compound
Ans: Nonmetals combine with each other to form covalent compounds, which exist as neutral molecules.
Q. Molecule
Ans: The smallest particle that has any of the properties of a compound
Q. Five states of Matter
Ans: Solids, liquids, gases, plasmas, and Bose-Einstein condensates
Q. PH Scale
Ans:
-pH Ranges from 1 to 14, with 7 considered to be neutral.
-pH less than 7 is said to be acidic
-pH greater than 7 are basic or alkaline.
Q. Acid
Ans: A substance that increases the hydrogen ion concentration of a solution.
Q. Base
Ans: A substance that decreases the hydrogen ion concentration in a solution.
Q. Pure substance
Ans: contains only one component and has characteristic properties
Q. mixture
Ans: contains many different components
Q. charge: +1, mass: 1
Ans: charge and mass of a proton
Q. charge: 0, mass :1
Ans: charge and mass of a neutron
Q. charge: -1, mass: 0
Ans: charge and mass of an electron
Q. more ___ you have, more ___ you need
Ans: protons, neutrons
Q. A reaction in which a neutral atom loses an outer electron is called
Ans: ionization reaction
Q. Ionization (losing an electron) reactions always __ energy
Ans: absorb
Q. the amount of energy absorbed in a ionization reaction is called _ ___ (symbol IE)
Ans: ionization energy
Q. A reaction in which a neutral atom gains an outer electron is called an __ reaction
Ans: electron attachment
Q. Electron attachment (gaining an electron) reactions normally _ energy
Ans: release
Q. The amount of energy released when an electron attaches to a neutral atom is called the _ (symbol EA)
Ans: electron affinity
Q. absorbing energy is a _ sign
Ans: positive
Q. releasing energy is a _ sign
Ans: negative
Q. __ electrons require unusually large amounts of energy to remove.
Ans: core
Q. Atoms or ions get _ as you go from left to right along a period of the Periodic Table.
Ans: smaller
Q. Atoms or ions get __ as you go down along a group of the Periodic Table.
Ans: bigger
Q. Anions (-1,-2,-3) are __ than a neutral atom of the same element.
Ans: larger
Q. why are does adding electrons (anions, -1,-2,-3) make the atom larger?
Ans: Adding extra electrons to an atom to make it an anion makes it bigger. Sometimes that’s because the new electrons must start another shell. But even if the new electrons don’t start a new shell, extra electrons “crowding in” among the rest increases the general repulsion among the electrons orbiting the nucleus. This pushes all the electrons apart from each other and makes the atom bigger.
Q. Cations (+1,+2,+3) are _ than a neutral atom of the same element.
Ans: smaller
Q. why does taking away electrons (cations +1,+2,+3) make an atom smaller?
Ans: Removing electrons from an atom to make it a cation makes it smaller. Sometimes that’s because the lost electrons are the last in a shell, and that means the atom now has one less layer of electrons. But even if the lost electrons aren’t the last in a shell, fewer electrons reduces the general repulsion among the electrons orbiting the nucleus. That allows all the electrons to come closer to the nucleus without “crowding” each other, and makes the atom smaller.
Q. How can I determine the relative energy of electron subshells? the expected rules for electron configurations are called __ rules (2s before 2p, 4f before 5d..etc.).
Ans: Madelung
Q. The idea is straightforward: “build up” the configuration by assigning each electron, one by one, to the lowest-energy unfilled quantum state available. (The German verb aufbauen means “to build up.”) That is, assign the first electron to one of the states in the 1s subshell. Then, assign the second electron to the other state in the 1s subshell, the third electron to one of the states in the 2s subshell, and so on:
Ans: aufbau
Q. What elements are exceptions to the madelung rule with instead of ns^2 mp^something it’s actually ns^1 mp^something+1 ?
Ans: Cu, Ag, Au, Cr, Mo, Nb, Ru, Rh,
Q. What’s the exception to the madelung rule with instead of ns^2 rd^8 it’s just rd^10 ?
Ans: Pd
Q. what’s the exception to the madelung rule with instead of ns^2 of^14 rd^8 it’s actually ns^1 of^14 rd^9 ?
Ans: Pt
Q. the usual five orbital labels for l = 2
Ans: dz2, dx2−y2, dxy, dxz, dyz
Q. When the de Broglie wavelength of an object is equal to or larger than its size, you need _ mechanics to describe it.
Ans: quantum
Q. When the de Broglie wavelength of an object is much smaller than its size, you can use _ mechanics.
Ans: classical
Q. What is the equation for de Broglie’s wavelength? lambda =
Ans: h / p (or h/(m*v) )
Q. distance from the nucleus (orbital A, B, or C) is what kind of probability?
Ans: radial
Q. distance from the axis of the 3D models of orbitals themselves is what kind of probability?
Ans: angular
Q. __ is the difference between the full nuclear charge (Z) and the amount of shielding (sigma) provided by other electrons
Ans: Effective nuclear charge
Q. he effective nuclear charge * experienced by a valence electron _ as you move from left to right along a period.
Ans: increases
Q. why does Effective Nuclear charge increase as you move from left to right
Ans: The answer is that when moving from element to element along the same period, electrons are being added to the same shell, and electrons in the same shell do not shield each other very well. Hence with each succeeding element along a period, increases by but increases by less than , so * gets bigger.
Q. What does Coulumb’s law calculate?
Ans: the strength of the powerful attractive electric force between an electron and a nucleus.
Q. The most important periodic trend in the effective nuclear charge Z (also ionization energy bc hard to let go when the attractive force is greater) experienced by valence electrons is that Z __ as we go from left to right in the Periodic Table, along a period.
Ans: increases
Q. SI prefixes
Ans: tetra (T) 10^12 m, giga (G) 10^9 m, mega (M) 10^6 m, kilo (K) 10^3 m, deci (d) 10^-1 m, centi (c) 10^-2 m, milli (m) 10^-3 m, micro (u) 10^-6 m, nano (n) 10^-9 m, pico (p) 10^-12 m
Q. mass to moles conversion
Ans: weight/molar mass (found on periodic table) = moles
Q. sig fig rules
Ans:
-non-zero digits and zeros in-between them are sig figs
-leading zeros (0.04) are not sig figs (start counting SF at first non-zero number)
-trailing zeros with a decimal are sig figs (without a decimal are not
-when multiplying/dividing by measurements, answer must have same number of sig fig as measurement with least number of sig fig
Q. scientific notation
Ans: A method of writing or displaying numbers in terms of a decimal number between 1 and 10 multiplied by a power of 10.
Q. isotopes
Ans: Atoms of the same element that have different numbers of neutrons (proton number stays the same always!!!)
Q. ionic compounds
Ans: compounds composed of cations and anions (typically metals and non-metals together)
Q. how to find binary ionic compounds when given 2 cations and 2 anions
Ans: create a table with cations on top, anions on the side, and pair the elements up while balancing charges to have a net charge of 0, similar to punnett squares) subscripts on elements always end up being absolute value of the opposite element’s charge
Q. calculating mass density
Ans: use D = M/V (1 cm^3 = 1mL)
Q. prefixes for naming molecular (covalent) compounds
Ans: mono 1, di 2, tri 3, tetra 4, penta 5, hexa 6, repta 7, octa 8, nona 9, deca 10 (ex. carbon dioxide)
Q. balancing chemical equations made easy ATOMS CANNOT BE CREATED OR DESTROYED – steps:
Ans:
-assign “1” as coefficient of compound with the most elements (if multiple, choose one)
-find an element that only shows up in one compound in the formula with an unknown coefficient and -assign a coefficient that balances the atoms of that element on both sides
-clear fractions by multiplying by a whole number
-check work
Q. how to multiply or divide scientific notation
Ans: multiply/divide mantissas and then add or subtract (depending on if multiplying or dividing scientific notations) the exponents on the 10s
Q. how to write chemical formula
Ans: name elements from left to right first, if in the same group, name the bottom element first. Hydrogen is written after most elements, but BEFORE groups 6A and 7A (ex: H2O)
Q. cations (+) have __ than electrons
Ans: more protons
Q. anions (-) have __ than electrons
Ans: less protons
Q. calculating molarity using solute moles
Ans: M (concentration/molarity) = mols of solute/volume
Q. Kelvins to celcius
Ans: Tk (kelvins) – 273.15 = Tc (celcius)
Q. how many important polyatomic ions
Ans: 15
Q. ammonium cation (poly)
Ans: NH4+
Q. hydronium cation (poly)
Ans: H3O+
Q. hydroxide anion (poly)
Ans: OH-
Q. acetate anion (poly)
Ans: C2H3O2-
Q. cyanide anion (poly)
Ans: CN-
Q. peroxide anion (poly)
Ans: O2 2-
Q. carbonate anion (poly)
Ans: CO3 2-
Q. nitrate anion (poly)
Ans: NO3-
Q. phosphate anion (poly)
Ans: PO4 3-
Q. sulfate anion (poly)
Ans: SO4 2-
Q. chlorate anion (poly)
Ans: ClO3-
Q. bromate anion (poly)
Ans: BrO3-
Q. iodate anion (poly)
Ans: IO3-
Q. chromate anion (poly)
Ans: CrO4 2-
Q. permanganate anion (poly)
Ans: MnO4-
Q. diatomic elements
Ans: H2, N2, O2, F2, Cl2, Br2, I2
Q. kinetic energy
Ans: energy of motion (more motion = more KE) – inversely proportional to PE
Q. potential energy
Ans: energy of position (higher biker = higher PE) – inversely proportional to KE
Q. unlike charges __ objects
Ans: attract
Q. like charges __ objects
Ans: repel
Q. oxoanion
Ans: an (polyatomic) anion in which an element is bonded to one or more oxygen atoms
Q. organization of periodic table
Ans: the elements into periods (rows) and groups (columns) by increasing atomic number. elements with similar properties are in the same group
Q. finding mole ratio from chemical formula
Ans: mole ratio of elements = atom ratio of elements
ex. moles of O/moles of Cl = atoms of O/atoms of Cl (solve for x)
Q. naming covalent compounds
Ans:
-name non-metal furthest to the left first
-name other one with elemental name + “-ide” ending
-use prefixes to name how many of both elements (first element doesn’t need “mono” but needs for all other prefixes)
Q. naming ionic compounds
Ans:
-name metal by elemental name
-name non-metal by elemental name + “-ide” ending
-name polyatomic ions by name
-write transition metal charges as roman numerals in parenthesis according to charge of other element
Q. isoprotonic atom
Ans: anions with the same number of protons (ex. N2-, N3-, N5- all have 7 protons, different election number)
Q. limiting reactant
Ans: A reactant that is totally consumed during a chemical reaction, limits the extent of the reaction, and determines the amount of product. it’s used up first!
Q. avogadro’s number
Ans: 6.02214 x 10^23
Q. pure substance
Ans: A sample of matter, either a single element or a single compound, that has constant chemical composition and definite chemical and physical properties — elements and compounds are a type of these.
Q. mixture
Ans: material composed of two or more elements or compounds that are physically mixed together but not chemically combined (example includes solutions)
Q. physical change
Ans: A change in a substance that does not involve a change in the identity of the substance
Q. chemical change
Ans: A change in a substance that creates a new substance with different material characteristics from those of the original substance
Q. Law of Conservation of Mass
Ans: Matter is not created nor destroyed in any chemical or physical change
Q. Law of Conservation of Energy and Mass
Ans: Energy cannot be created or destroyed
Q. Dalton’s Atomic Theory
Ans:
-elements are composed of atoms.
-atoms of same element are identical, but differ from other elements.
-elements can mix together
-atoms only change when mixed with other elements
Q. Gold Foil Experiment (Rutherford)
Ans: When a beam of alpha particles strikes gold foil, most pass straight through, but some are scattered; the reason for this is presence of a nucleus
Q. the more electronegative an atom…
Ans: the more stable the anion.
Q. electronegativity
Ans: A measure of the ability of an atom in a chemical compound to attract electrons
Q. electronegativity trend
Ans: increases up and to the right
Note: Chemistry questions in ALEKS are prepared by professional chemistry professors whose areas of expertise give the program the ability to ask questions that are both challenging and beneficial to the learning process.
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