Unit 2 Chemistry Test (Have to look at past test for diagrams) Flashcards
The diagram represents a gaseous sample of matter in a sealed container. Each circle of a different shade represents a different type of atom. Which of the following best describes the particle diagram?
A
It represents three different compounds mixed together with one element.
B
It represents one compound mixed together with three different elements.
C
It represents four different elements, and no compounds are represented.
D
It represents a single compound composed of three elements.
B
Three elements are represented, two of them diatomic. A compound composed of two different types of atoms is also represented.
⚫ - model 1 ~ Helium
🟢🟢 - model 2 ~Oxygen
Consider the models shown. Drag the word that best describes each model to the corresponding box.
Molecule Compound Atom
⚫ - model 1 ~ Helium is an Atom
🟢 - model 2 ~Oxygen is a molecule
◒ → ◍ ← ◒
During a demonstration, a teacher makes a mixture by combining 40mL of methanol and 60mL of water, as shown. The teacher asks students to describe what happens so that they can create a model together.
Based on the particle diagram, what will be observed?
A
Methanol and water molecules will form two layers with methanol on the top.
B
Methanol and water molecules will form two layers with methanol on the bottom.
C
Methanol and water molecules will not form layers.
D
The methanol and water molecules will combine to form a new substance.
C
Methanol and water molecules will not form layers.
The particle diagram shows that the methanol molecules and water molecules are mixed together.
paGas chromatography is an analytical technique that is used to separate and analyze samples that can be vaporized without decomposing. The chromatography column contains a substance that helps separate the sample being analyzed. The sample is vaporized and carried through the column by an inert gas. As the mixture moves through the column, the compounds are separated based on how much they interact with the substance in the column. The molecules of each compound are detected as they exit the column, and a peak for each compound is produced on a chromatogram. The area under each peak on the chromatogram is proportional to the concentration of the compound in the sample. A chromatogram produced by separating a mixture of compounds is shown.
Based on the information given, which of the following statements about the chromatogram is most likely true?
A
The three peaks each represent a different element.
B
The three peaks each represent a different substance used to separate the compounds in the sample.
C
The compound represented by peak A interacted the most with the substance in the column.
D
The sample contained more of the compound represented by peak B than of that represented by peak C.
D
The sample contained more of the compound represented by peak B than of that represented by peak C .
The amount of each compound in the sample is proportional to the area of each peak, so there was more of compound B in the sample.
The compounds in the sample do not decompose. Each peak represents a different compound.
A student claims that intermolecular forces are overcome when water boils, but intramolecular forces are not. Which of the following particle diagrams can be used to support the claim?
A
The figure presents a particle diagram, with liquid water molecules composed of two hydrogen atoms and one oxygen atom at the bottom of the diagram. At the top of the diagram, there are individual hydrogen and oxygen atoms spaced far apart.
B
The figure presents a particle diagram, with liquid water molecules composed of two hydrogen atoms and one oxygen atom at the bottom of the diagram. At the top of the diagram, there are O 2 molecules and H 2 molecules spaced far apart.
C
The figure presents a particle diagram, with liquid water molecules composed of two hydrogen atoms and one oxygen atom at the bottom of the diagram. At the top of the diagram, there are H 2 O molecules, O 2 molecules, and H 2 molecules spaced far apart.
D
The figure presents a particle diagram, with liquid water molecules composed of two hydrogen atoms and one oxygen atom at the bottom of the diagram. At the top of the diagram, there are H 2 O molecules spaced far apart.
D
Correct. When water boils, water molecules do not break apart. The molecules move farther apart, and H2O (liquid) simply becomes H2O( gas).
The figure shows two Lewis diagrams, one of pentane and one of octane. The pentane diagram contains a chain of five C atoms, which are connected to each other by single bonds. The first C atom is connected to 3 H atoms by single bonds. The second, third, and fourth C atoms are each connected to 2 H atoms by single bonds. The fifth C atom is connected to 3 H atoms by single bonds. The octane diagram contains a chain of eight C atoms, which are connected to each other by single bonds. The first C atom is connected to 3 H atoms by single bonds. The second through seventh C atoms are each connected to 2 H atoms by single bonds. The eighth C atom is connected to 3 H atoms by single bonds.
The Lewis diagrams of pentane and octane are shown. Which of the following indicates which compound has greater intermolecular forces and explains why?
A.
Pentane, because it has a smaller molecular size, resulting in a greater concentration of electrons.
B
Pentane, because it has a smaller molecular size, resulting in more dipole-dipole interactions.
C
Octane, because it has more electrons, resulting in greater London dispersion forces.
D
Octane, because it has more hydrogen atoms, resulting in more hydrogen bonding interactions.
C
Octane, because it has more electrons, resulting in greater London dispersion forces.
London dispersion forces are generally greater when the electron clouds of the molecules are larger (greater polarizability).
Which of the following diagrams shows a hydrogen bond circled?
A.
The figure presents a structural formula that has a C atom connected to 3 H atoms and one O atom by single bonds. The O atom has two pairs of nonbonding electrons, and it is connected to an H atom by a single bond. The single bond between the O atom and the H atom is circled.
B
The figure presents a structural formula of two molecules connected by a long dashed line. The first molecule contains a C atom connected to 3 H atoms and one F atom by single bonds. The F atom has 3 pairs of nonbonding electrons. The second molecule contains a C atom connected to 4 H atoms by single bonds. The F atom in the first molecule is connected to an H atom in the second molecule by a long dashed line. The long dashed line is circled.
C
The figure presents a structural formula of two molecules connected by a long dashed line. The first molecule contains a C atom connected to 3 H atoms and one O atom by single bonds. The O atom has two nonbonding pairs of electrons, and is connected to an H atom by a single bond. The second molecule has the same formula and structure as the first molecule. One of the H atoms bonded to the C atom in the first molecule is connected by a long dashed line to one of the H atoms bonded to the C atom in the second molecule. The long dashed line is circled.
D
The figure presents a structural formula of two molecules connected by a long dashed line. The first molecule contains a C atom connected to 3 H atoms and one O atom by single bonds. The O atom has two nonbonding pairs of electrons, and is connected to an H atom by a single bond. The second molecule has the same formula and structure as the first molecule. The O atom in the first molecule is connected by a long dashed line to the H atom in the second molecule that is connected to the O atom in the second molecule. The long dashed line is circled.
D
Hydrogen bonds are intermolecular forces. The hydrogen atom participating in the hydrogen bond is covalently bonded to an oxygen atom, which is highly electronegative. The hydrogen atom is attracted to the oxygen atom in another molecule.
A hydrogen bond is an intermolecular force, not a bond between atoms in the same molecule.
The figure presents Lewis diagrams of C H 4 and C H 3 O H. The C H 4 Lewis diagram shows a C atom connected to 4 H atoms by single bonds. The C H 3 O H Lewis diagram shows a C atom connected to 3 H atoms and one O atom by single bonds. The O atom has two nonbonding pairs of electrons, and is connected to an H atom by a single bond.
The Lewis diagrams of CH4 and CH3OH are shown. Which of the following statements about intermolecular forces in CH4(l) and CH3OH(l) best explains the fact that the boiling point of CH3OH(l) is higher than that of CH4(l)?
A
The London dispersion forces in CH3OH(l) are much greater than those in CH4(l).
B
The London dispersion forces in CH4(l) are much greater than those in CH3OH(l).
C
CH3OH(l) can form hydrogen bonds, but CH4(l) cannot.
D
The hydrogen bonding in CH4(l) is stronger than that in CH3OH(l).
C
Hydrogen bonding in CH3OH is a much stronger intermolecular force than the London dispersion forces in CH4.
Which of the following best explains the difference in the solubility in water of the alcohols listed in the table?
A
Each molecule contains an −OH group and can form hydrogen bonds with water molecules.
B
As the size of the nonpolar portion of the alcohol increases, the solubility in water decreases.
C
The solubility of the alcohols in water increases as the number of hydrogen bonds they can form with water increases.
D
Molecules with more carbon atoms tend to be more soluble in water.
B
The end of the alcohol molecule with the −OH group is polar and the −OH group forms hydrogen bonds with water molecules. However, the nonpolar end of the molecules increases in size as solubility in water decreases, and this accounts for the trend.
A chemist uses distillation to remove some methanol from a mixture of equal parts methanol and water. The chemist heats the mixture and collects some of the first gas produced. A representative sample of the liquid and gas are shown in the particulate views.
Which of the following explains the composition of the gas?
A
The covalent bonds in methanol are weaker than those in water, so methanol has a lower boiling point than water has.
B
The covalent bonds in methanol are stronger than those in water, so methanol has a higher boiling point than water has.
C
The intermolecular forces between methanol molecules are weaker than those between water molecules, so methanol has a lower boiling point than water has.
D
The intermolecular forces between methanol molecules are stronger than those between water molecules, so methanol has a higher boiling point than water has.
C
There is more methanol in the gas, so it must be easier to separate liquid methanol molecules from each other than to separate liquid water molecules from each other. Therefore, the intermolecular forces between water molecules must be greater than those between methanol molecules, and water must have a higher boiling point than methanol has.
A chemist uses distillation to remove some methanol from a mixture of equal parts methanol and water. The chemist heats the mixture and collects some of the first gas produced. A representative sample of the liquid and gas are shown in the particulate views.
If the total pressure of the gas sample is 1.0atm, the partial pressure of H2O(g) in the gas sample produced is predicted to be closest to which of the following?
A
0.10atm
B
0.50atm
C
0.90atm
D
1.0atm
A
There is one molecule of water and there are nine molecules of methanol, so the partial pressure of water must be one-tenth the total pressure, or 0.10×1.0atm=0.10atm.
Which of the following is the complete Lewis diagram of NF3?
C
There are 26 valence electrons accounted for in the Lewis diagram and each atom has a complete octet.
The figure shows a Lewis electron-dot diagram of a molecule, which consists of one N atom and three H atoms. The three H atoms are each connected to the N atom by single bonds. The N atom has one nonbonding pair of electrons.
A Lewis diagram of ammonia is shown. Which of the following claims about the polarity of the ammonia molecule is correct?
A
The molecule is polar because there is a concentration of electrons near the nitrogen atom.
B
The molecule is polar because it contains more hydrogen atoms than nitrogen atoms.
C
The molecule is nonpolar because there is a lone pair of electrons on the nitrogen atom.
D
The molecule is nonpolar because the electrons on the nitrogen atom are pulled toward the hydrogen atoms in the molecule.
A
The electron pair on the nitrogen atom creates an unequal distribution of electrons in the molecule, resulting in a dipole.
The figure presents Lewis diagrams of chloromethane and methane. The diagram for chloromethane shows a carbon atom connected to three hydrogen atoms and one chlorine atom by single bonds. The chlorine atom has three nonbonding pairs of electrons. The diagram for methane shows a carbon atom connected to four hydrogen atoms by single bonds.
Based on the molecular structures of chloromethane and methane shown, a student makes the claim that a pure sample of chloromethane has stronger intermolecular forces than a pure sample of methane has.
Which of the following statements correctly uses reasoning to support the student’s claim?
A
Chloromethane has a polar C–Cl bond, which allows for dipole-dipole interactions, but methane is nonpolar and only experiences dispersion forces.
B
Chloromethane experiences stronger dipole-dipole interactions than methane does because the dipole of the C–Cl bond is canceled by the dipole from the C–H bonds.
C
Chloromethane has stronger dispersion forces than methane has because of the nonpolar C–Cl bond in chloromethane.
D
Chloromethane has stronger dispersion forces than methane has due to the highly polar C–H bonds in chloromethane.
A
The C–Cl bond is polar, which results in a permanent dipole in a molecule of chloromethane and dipole-dipole interactions between molecules. A molecule of methane is nonpolar, and the interactions between molecules are London dispersion forces.
The figure shows a Lewis electron-dot diagram of a molecule, which consists of one C atom connected to two H atoms and two C l atoms by single bonds. The two H atoms are directly to the left and right of the C atom. The two C l atoms are directly above and below the C atom, and each C l atom has three nonbonding pairs of electrons.
A student claims that the molecule represented in the diagram is nonpolar, so the substance has only London dispersion forces. Which of the following is the best evaluation of the student’s claim?
A
The claim is correct; the dipoles cancel.
B
The claim is correct; the atoms all lie on the same plane.
C
The claim is incorrect; the geometry is tetrahedral and there are two different types of atoms around the C atom, so the dipoles do not cancel.
D
The claim is incorrect; the atoms all lie on the same plane, so the dipoles cancel.
C
Based on the tetrahedral arrangement of Cl and H atoms around the C atom, the bond dipoles do not cancel.
It is also Polar
