Q&A Hero

Q: If you filter sea water to remove all of the particles you would be left with a clear A) homogeneous mixture called a solution. B) homogeneous mixture called a suspension. C) heterogeneous mixture called a solution. D) heterogeneous mixture called a suspension. E) pure liquid.

Q: Which of the following would be considered a homogeneous mixture? A) wine B) hydrogen cyanide C) rusty iron D) pretzel E) sugar

Q: How would you classify the following material? swimming pool water A) homogeneous mixture B) heterogeneous mixture C) a pure element D) a pure compound E) depends on how many children have been in it

Q: Which of the following is a pure substance? A) baking soda B) salt water C) cooking oil D) duct tape E) orange juice

Q: Which of the following would be considered a heterogeneous mixture? A) salad dressing B) water C) milk D) vegetable oil E) vinegar

Q: Many dry cereals are fortified with iron, which is added to the cereal in the form of small iron particles. How might these particles be separated from the cereal? A) add water and the iron particles will float to the top B) blend the cereal to a fine consistency and pass through a filter C) collect the iron filings with a magnet D) heat the cereal so that the iron particles melt and thereby coalesce

Q: Half-frozen fruit punch is always sweeter than the same fruit punch completely melted because A) the sugar sinks to the bottom. B) crystallization is a purifying process. C) the half-frozen fruit punch is warmer. D) sugar molecules are less soluble in a half-frozen solution.

Q: Why can't the elements of a compound be separated from one another by physical means? A) They are too homogeneous when found within a compound. B) Their atoms are too tightly bound to one another. C) Elements found within a compound tend to be inert. D) Elements tend not to be soluble in water.

Q: Mixtures can be separated into their components by taking advantage of differences in the chemical properties of the components. Why might this separation method be less convenient than taking advantage of differences in the physical properties of the components? A) A chemical property involves a chemical change so that you no longer have what you had. B) Chemical properties are not as apparent as are physical properties. C) The chemical properties of the components of a mixture are too similar to each other. D) The chemical properties of the components of a mixture are too different from each other.

Q: How might you separate a mixture of sand and salt? A) with tweezers and a magnifying glass B) just add water C) heat the mixture until one of the components melts D) Two of the above answers are reasonable.

Q: What is the difference between a compound and a mixture? A) They both consist of atoms from different elements. B) The way in which their atoms are bonded together. C) One is a solid and the other is a liquid. D) The components of a mixture are not chemically bonded together.

Q: Each circle represents an atom. Which of the following boxes contains an element? A compound? A mixture? A) element: A, C; compound: A, B, C; mixture: A, B B) element: C; compound: A, B; mixture: B C) element: A, C; compound: A, B; mixture: A D) element: A, C; compound: A, B; mixture: A, B

Q: A combination of two or more substances in which they no longer retain their chemical properties is called a(n) A) mixture. B) compound. C) heterogeneous mixture. D) periodic trend. E) suspension.

Q: The following image represents which kind of matter? A) a compound B) a mixture C) an element D) none of the above E) all of the above

Q: The following image represents which kind of matter? A) a mixture B) a compound C) an element D) none of the above E) all of the above

Q: Which of the following is a mixture? A) air B) gold C) salt D) iron E) helium

Q: What is the difference between a compound and a mixture? A) A mixture can be physically separated into its components; a compound cannot be physically separated into its components. B) A compound can be physically separated into its components; a mixture cannot be physically separated into its components. C) A compound is just a mixture of elements. D) The components of a mixture do not have the same properties individually as they do when mixed. E) The components of a compound have the same properties individually as they do when mixed.

Q: Which bond is most polar? A) H-N B) N-C C) C-C D) O-H

Q: Atoms of metallic elements can form ionic bonds, but they are not very good at forming covalent bonds. Why? A) These atoms are too large to be able to come in close contact with other atoms. B) They have a great tendency to lose electrons. C) Their valence shells are already filled with electrons. D) They are on the wrong side of the periodic table.

Q: Atoms of nonmetallic elements form covalent bonds, but they can also form ionic bonds. How is this possible? A) This happens when one of the bonded nonmetallic elements has a strong electronegativity. B) It happens when one of the nonmetallic elements loses an electron to become a positive ion. C) An ionic bond results when a nonmetallic elements loses an electron to a metallic element. D) An ionic bond results when a nonmetallic elements gains an electron from a metallic element.

Q: In terms of the periodic table, is there an abrupt or gradual change between ionic and covalent bonds? A) There is an abrupt change that occurs across the metalloids. B) Actually, any element of the periodic table can form a covalent bond. C) There is a gradual change: the farther apart, the more ionic. D) Whether an element forms one or the other depends on nuclear charge and not the relative positions in the periodic table.

Q: The source of an atom's electronegativity is the A) repulsive force occurring among electrons within the same shell. B) repulsive force occurring between electrons within neighboring shells. C) positively charged atomic nucleus. D) kinetic energy electrons have orbiting the nucleus.

Q: Does an ionic bond have a dipole? A) No, dipoles are only found in covalent compounds. B) No, but the electrical charges are relatively strong. C) Yes, the ionic bond is an example of a very strong dipole. D) Yes, but for ionic compounds they are referred to as monopoles.

Q: Which of the following compounds has polar covalent bonds? A) H2O B) CsF2 C) S8 D) Ne E) CH4

Q: Which of the following bonds would be the least polar? A) C-F B) C-O C) C-Cl D) C-H E) All are equally polar.

Q: Which of the following bonds would be the most polar? A) C-F B) C-Cl C) C-Br D) C-I E) All are equally polar.

Q: Which of the following molecules contains a polar bond? A) H-F B) Cl-Cl C) H-H D) F-F E) all of the above

Q: Which of the following molecules would contain a dipole? A) H-F B) Cl-Cl C) H-H D) F-F E) all of the above

Q: Which of the following statements best describes a relatively polar bond? A) a very electronegative atom and a weakly electronegative atom are covalently bound B) two very electronegative atoms are covalently bound C) two very electronegative atoms undergo ionic bonding D) two weakly electronegative atoms undergo ionic bonding E) none of the above

Q: Which of the following substances is pure? A) an ionic compound consisting of sodium and chlorine ions B) a covalent compound consisting of one type of molecule C) an element D) all of the above E) none of the above

Q: Classify the following bonds as ionic, covalent, or neither (O, atomic number 8; F, atomic number 9; Na, atomic number 11; Cl, atomic number 17; U, atomic number 92). O with F Ca with Cl Na with Na A) covalent, ionic, covalent B) ionic, covalent, neither C) neither, ionic, covalent D) covalent, ionic, neither

Q: Which of the following statements is untrue? A) Covalent molecules are never crystalline. B) Covalent molecules usually have low melting points. C) Covalent molecules can have nonbonding electrons. D) Covalent bonds can involve more than one pair of electrons. E) All of the above statements are true.

Q: How many covalent bonds would the following atom usually form? A) 3 B) 2 C) 1 D) 5 E) would usually not form any covalent bonds

Q: How many covalent bonds would the following generic atom usually form? A) 1 B) 2 C) 4 D) 8 E) would usually not form any covalent bonds

Q: How many covalent bonds would the following atom usually form? A) 1 B) 2 C) 4 D) 6 E) It would tend to form ionic bonds.

Q: How many nonbonding pairs of electrons are in the following molecule? HH A) 1 pair B) 6 pairs C) 0 pairs D) 8 pairs E) none of the above

Q: What does the line in the following example actually represent? HH A) a shared pair of electrons B) a covalent bond C) an ionic bond D) a pair of nonbonding electrons E) A and B

Q: What it the main difference between an ionic and a covalent bond? A) One is the sharing of a pair of electrons, the other is the transfer of at least one electron. B) One involves electrons, the other does not involve any electrons. C) The electrons in both types of bonding undergo an exchange. D) The electrons are traded between the two atoms and this keeps the atoms close. E) Both bonds are the same, but named different to describe different atoms involved.

Q: What is a molecule? A) a group of atoms that are held together by covalent bonds B) a group of atoms that are held together by ionic bonds C) pair of atoms sharing a set of valence electrons D) pair of shared valence electrons E) group of covalent compounds held together by ionic bonds

Q: Why is metal shiny? A) The loose electrons reflect most wavelengths of light. B) The electrons transmit most wavelengths of light. C) The electrons absorb each light wave. D) The electrons emit light due to electronic excitation. E) all of the above

Q: What property of alloys make them ideal for developing new materials? A) The characteristics of the material change depending on how much of each component is present. B) Alloys are very rigid and are extremely resistant to chemical decomposition. C) The size of the atoms involved is directly related the electrical conductivity. D) all of the above E) none of the above

Q: If the concentration of gold in seawater is 2.0 milligram per ton of sea water and the mass of the ocean is 1.5 1018 tons, how much gold is in the ocean? A) 3.0 1012 kg B) 3.0 kg C) 300 g D) 36 mg E) 3000 lb

Q: There is more gold in 1 km3 of the ocean than the amount of gold mined in all of recorded history. How come we do not mine the oceans? A) It is too dilute to separate. B) It would take too much energy. C) It would cost too much. D) all of the above E) none of the above

Q: Why is it better to recycle metals than to mine more? A) It takes far less energy to recycle. B) Mining is less expensive than recycling but not environmentally friendly. C) Ores contain toxic elements. D) all of the above E) none of the above

Q: Why are ores so valuable? A) They are sources of naturally occurring gold. B) Metals can be efficiently extracted from them. C) They tend to occur in scenic mountainous regions. D) They hold many clues to Earth's natural history.

Q: Distinguish between a metal and a metal-containing compound. A) There is no distinction between the two. B) Only one of these contains ionic bonds. C) Only one of these contains covalent bonds. D) Only one of these occurs naturally.

Q: Given that the total number of atoms on our planet remains fairly constant, how is it ever possible to deplete a natural resource such as a metal? A) The problem remains that not everyone recycles as they should. B) Recycling only forestalls the inevitable depletion of metal resources. C) The atoms don't leave our planet, which is why naturally occurring materials never really reach the point of depletion. D) The problem is with the expense of collecting metal atoms that are uniformly dispersed.

Q: Which of the following describes how a metal atoms behaves in a bulk metallic object? A) The metal ion shares its outermost electrons freely with its neighbors. B) The metal atoms have limited interaction with neighboring atoms. C) The metal atom shares its electrons in a very directional manner. D) The metal atom shares its electrons with only one other atom. E) none of the above

Q: What property of metal atoms account for many of the observed bulk phenomena seen in metal samples? A) Metal atoms easily lose one or more outer electrons. B) Metal atoms easily gain one or more outer electrons. C) Metals readily form ionic bonds. D) Metals readily form covalent bonds. E) none of the above

Q: Metals are often used for making designer jewelry because they A) do not conduct heat well. B) conduct electricity. C) are shiny. D) are strong but can be bent. E) c and d

Q: Metals are useful for the structural support of buildings because they A) do not conduct heat well. B) are shiny. C) conduct electricity. D) are strong but can be bent. E) c and d

Q: Which of the following is not a property of metal? A) does not conduct heat well B) conducts electricity C) is shiny D) is strong, but can be bent E) All of the above are properties of metals.

Q: crystals are composed of A) units of molecules held together by dipole interactions. B) groups of ions and molecules. C) units composed of six Mg atoms and six molecules. D) a multitude of ions and ions grouped together in a three-dimensional array with a 1:2 ratio of to . E) a two-dimensional array of [-Mg-Cl-Cl-] units.

Q: Which would you expect to have a higher melting point: sodium chloride, NaCl, or cesium chloride, CsCl? Why? A) The cesium chloride has a higher melting point because larger ions of the same charge are able to attract more ions of the opposite charge. B) The cesium chloride has a higher melting point because its ions are smaller, which makes the charges more dense. C) The sodium chloride has a higher melting point because of the greater charges of the ions, and hence the greater force of attractions between them. D) The sodium chloride has a higher melting point because its ions are smaller, which allows oppositely charged ions to get closer.

Q: Which of the following does not describe ionic compounds? A) They have a tendency to melt easily. B) They consist of positive and negative ions. C) They are held together by electrostatic attraction. D) They are usually very ordered. E) none of the above

Q: Which of the following substances contains ions? A) B) C) D) E) all of the above

Q: Which of the following compounds contains ionic bonds? A) B) O C) D) E) none of the above

Q: Magnesium ions carry a 2+ charge, and chloride ions carry a 1- charge. What is the chemical formula for the ionic compound magnesium chloride? A) MgCl B) Cl C) Mg D)

Q: Barium ions carry a 2+ charge, and nitrogen ions carry a 3- charge. What would be the chemical formula for the ionic compound barium nitride? A) B) C) D)

Q: What molecule loses a proton to form the hydroxide ion, OH⁻? A) the oxygen molecule, B) the water molecule, O C) the hydrogen peroxide molecule, D) the hydrogen molecule,

Q: Is an ionic compound an example of a chemical compound, or is a chemical compound an example of an ionic compound? A) An chemical compound is an example of a ionic compound. B) Neither is an example of the other. C) Each is an example of the other. D) An ionic compound is an example of a chemical compound.

Q: Which would you expect to have a higher melting point: sodium chloride, NaCl, or aluminum oxide, ? A) The aluminum oxide has a higher melting point because it is a larger molecule and has a greater number of molecular interactions. B) NaCl has a higher melting point because it is a solid at room temperature. C) The aluminum oxide has a higher melting point because of the greater charges of the ions, and hence the greater force of attractions between them. D) The aluminum oxide has a higher melting point because of the covalent bonds within the molecule.

Q: Which are closer together: the two nuclei within potassium fluoride, KF, or the two nuclei within molecular fluorine, ? A) KF B) C) Both are the same. Any atom bonded to F will have the same inter-nuclear separation. D) It makes little sense to compare two molecules which exist in different physical states. KF is a solid while is a gas.

Q: How many chloride ions (Cl-1) are needed to balance the positive charge of a barium ion (Ba+2)? A) 2 B) 1 C) -2 D) -1 E) 3

Q: How many oxide ions (O-2) are needed to balance the positive charge of a titanium ion (Ti+4)? A) 2 B) 1 C) 3 D) 4 E) 6

Q: If you mix a typical iodine ion (I, atomic no. = 53) with a typical barium ion (Ba, atomic no. = 56), what compound is formed? A) BaI2 B) BaI C) Ba56I53 D) Ba2I E) Ba2I2

Q: If you mix a typical aluminum ion (Al, atomic no. = 13) with a typical oxygen ion (O, atomic no. = 8), what compound is formed? A) Al2O3 B) Al3O2 C) Al13O8 D) Al3O E) Al2O2

Q: What is the compound that forms if you react potassium and sulfur? A) K2S B) KS C) SP D) PS2 E) SkP

Q: If the following generic atom were to undergo ionization, what would be the charge of most likely product? A) +3 B) -3 C) -5 D) 8 E) would probably not ionize

Q: If the following generic atom were to undergo ionization, what would be the charge of the most likely product? A) +2 B) -2 C) -6 D) +6 E) would probably not ionize

Q: If the following generic atom were to undergo ionization, what would the most likely product be? A) +1 B) -2 C) -3 D) +4 E) would probably not ionize

Q: Which of the following molecules contains an ionic bond? A) MgCl2 B) Cl2 C) SF3 D) PO4-3 E) none of the above

Q: Which of the following best describes ionic bonding? A) two atoms sharing a set of electrons B) two atoms exchanging a set of electrons C) one atom giving up some of its electrons to another atom D) when two elements with same charge are held together by electrostatic forces E) none of the above

Q: Take money away from your bank account and the bank will show a negative credit. Take an electron away from an atom, however, and the atom shows up positive. Explain. A) Electrons are already negative. Therefore, we know from basic math that subtracting a negative (number) from a neutral (atom), will make the result positive. B) Neutral atoms contain identically charged but oppositely signed protons and electrons. Removing one of the negative electrons results in an excess of positively charged protons. C) Removing an electron from an atom does not have the atom show up positive. It simply leaves the atom short one electron. D) Atoms are constantly exchanging electrons. Having an atom "show up positive" is only an expression indicating that it has taken its turn in the game of electron exchange.

Q: Why does an atom with many valence electrons tend to gain electrons rather than lose any? A) Atoms with many valence electrons tend to have relatively weak forces of attraction between the valence electrons and the nucleus. Therefore, the outer electrons are free to attract other electrons. B) There is stability in numbers. Atoms with many valence electrons are always attracting new electrons. C) The old adage that "he who has, gets" is also true in atomic structure. Atoms with many valence electrons can essentially overpower atoms with few valence electrons and attract additional electrons. D) Atoms with many valence electrons tend to have relatively strong forces of attraction between the valence electrons and the nucleus. This makes it easy for them to gain additional electrons.

Q: Which should be larger, the potassium atom, K, or the potassium ion, K⁺? A) The potassium ion, K⁺ is larger since charging an atom always makes it larger. B) The potassium atom, K, with an additional shell of electrons is larger. C) The potassium ion, K⁺ is larger since it has an extra electron which increases its size. D) The potassium atom and the potassium ion are exactly the same size and only differ in charge.

Q: Why doesn't the sodium atom gain seven electrons so that its third shell becomes the filled outermost shell? A) It would be too difficult for another atom to lose seven electrons. B) Only six additional electrons are required to fill the outermost shell of sodium. C) In gaining seven more electrons, sodium's fourth outer shell becomes filled. D) Sodium's nuclear charge is not strong enough to hold that many more electrons.

Q: The neon atom tends not to gain any additional electrons because A) its nuclear charge is not great enough. B) that would result in a positive ion. C) of the repulsions they would experience with electrons in the same shell. D) there is no more room available in its outermost occupied shell.

Q: The neon atom tends not to lose any electrons because A) of its relatively strong effective nuclear charge. B) that would result in a negative ion. C) its electrons are paired together within the same orbitals. D) the ionization energy is so high.

Q: Which of the following is NOT an ion? A) H+1 B) Br- C) O2 D) Mg+2 E) NO3-