Chem midterm quizlet

The pressure, in atm, exerted by 1.85 mol of an ideal gas placed in a 3.00 L container at 35.0⁰C is given by which of following expressions?

(1.85)(0.0821)(308)/3.00

A mixture of CO(g) and O2(g) is placed in a container as shown above. A reaction occurs forming CO2(g) which of the following best represents the contents of the box after the reaction has proceeded as completely as possible?

(2) CO2 and (4) O2

14. 2 NO(g) + O2(g) → 2 NO2(g)A possible mechanism for the overall reaction represented above is the following:(1) NO(g) + NO(g) → N2O2(g) slow(2) N2O2(g) + O2(g) → 2NO2(g) fastWhich of the following rate expressions agrees best with this possible mechanism?(A) Rate = k[NO]2(D) Rate = k[NO]2[O2](B) Rate = k[NO](E) Rate = k[N2O2][O2][O2](C) Rate = k[NO]2[O2]

(A)Rate=k[NO]2

In which of the following species does sulfur have the same oxidation number as it does in H2SO4?(A) H2SO3(B) S2O32-(C) S2-(D) S8(E) SO2Cl2

(B)S2O32-

A 0.10 M aqueous solution of sodium sulfate, Na2SO4 , is a better conductor of electricity than a 0.10 M aqueous solution of sodium chloride, NaCl. Which of the following best explains this observation?

(C) More moles of ions are present in a given volume of 0.10 M Na2SO4 than in the same volume of 0.10 M NaCl.

2H2O(l) + 4MnO4-(aq) + 3ClO2-(aq) ( 4MnO2(s) + 3ClO4-(aq) + 4OH-(aq)According to the balanced equation above, how many moles of ClO2-(aq) are needed to react completely with 20. mL of 0.20 M KMnO4 solution?

0.0030 mol

How many carbon atoms are contained in 2.8g of C2H4?

1.2 x 10^23

A student prepares a solution by dissolving 60.00 g of glucose (molar mass 180.2 g mol-1) in enough distilled water to make 250.0 mL of solution. The molarity of the solution should be reported as

1.332 M

Which of the following ground-state electron configurations represents the atom that has the lowest first-ionization energy?

1s2 2s2 2p6 3s1

Based on periodic trends and the data in the table below, which of the following are the most probable values of the atomic radius and the first ionization energy for potassium, respectively?

242 pm, 419 kJ/mol

How many protons, neutrons, and electrons are in an Fe-56 atom?

26 protons 30 neutrons 26 electrons

A wavelength of 510 nm corresponds to an approximate frequency of 6 x 1014 s-1. What is the approximate energy of one photon of this light?

4 x 10^-19 J

H3AsO4 + 3I−+ 2 H3O+ H3AsO3 + I3− + H2OThe oxidation of iodide ions by arsenic acid in acidic aqueous solution occurs according to the stoichiometry shown above. The experimental rate law of the reaction is: Rate = k [H3AsO4] [I−] [H3O+]25. What is the order of the reaction with respect to I−?(A) 1 (B) 2 (C) 3 (D) 5 (E) 6

A

Which of the following best describes the type of bonding in cesium chloride, CsCl(s)?

A lattice of positive and negative ions held together by electrostatic forces

Atoms of Mg combine with atoms of F to form a compound. Atoms of which of the following elements combine with atoms of F in the same ratio?

Ba

A student mixes 20.0g of white KCl crystals with distilled water in a beaker. After the mixture was stirred, no crystals are visible and the solution is clear. After several days, all of the water evaporates and white crystals are found in the beaker. Which of following pieces of experimental evidence would best help the student to confirm that a new compound had not been made and that only a physical change occurred?

After the water has evaporated, the white crystals in the beaker have a mass of 20.0g.

The interaction energy of two hydrogen atoms is shown on the graph above. Which of the answer choices displayed on the graph best represents the bond length of the H2 molecule?

B

The structure of one form of boron nitride is represented below. This form of boron nitride is one of the hardest substances known. Which of the following best helps explain why boron nitride is so hard?

Boron nitride is a network solid of atoms connected by covalent bonds with fixed bond angles.

The table above shows the structural formulas and molar masses for three different compounds. Which of the following is a list of the compounds in order of increasing boiling points?

Butane < acetone < 1-propanol

A 23.0g sample of a compound contains 12.0g of C, 3.0g of H, and 8.0g of O. Which of the following is the empirical formula of the compound?

C2H6O

Which of the following molecules has a dipole moment of zero?

C6H6 (benzene)

Which of the following species does not contain a pi bond?

CH4

Which of the following is a nonpolar molecule that contains polar bonds?

CO2

The photoelectron spectrum of the 1s electrons of two isoelectronic species, Ca2+ and Ar, are shown below. Which of the following correctly identifies the species associated with peak X and provides a valid justification?

Ca2+, because its nucleus has two more protons that the nucleus of Ar has

Equal volumes of solutions in two different vessels are represented below. If the solution represented in vessel is KCl (aq), then the solution represented in vessel 2 could be an aqueous solution of

CaCl2 with twice the molarity as the solution in vessel 1

Which of the following best describes the type of bonding in a sample of gold, Au(s)?

Closely packed lattice with delocalized electrons throughout

Which of the following represents a pair of isotopes?

D I. II.

C3H8(g) + 4 Cl2(g) C3H4Cl4(g) + 4 HCl(g)A 6.0 mol sample of C3H8(g) and a 20. mol sample of Cl2(g) are placed in a previously evacuated vessel, where they react according to the equation above. After one of the reactants has been totally consumed, how many moles of HCl(g) have been produced?

D) 24 mol

Which of the following is the net ionic equation for the reaction between aqueous sodium fluoride and hydrochloric acid? a. NaF(aq)+HCl(aq)→NaCl(aq)+HF(aq) b. Na+(aq)+F−(aq)+H+(aq)+Cl−(aq)→Na+(aq)+Cl−(aq)+HF(aq) c. Na+(aq)+Cl−(aq)→NaCl(aq) d. F- (aq)+H+(aq)→HF(aq)

D. F- (aq)+H+(aq)→HF(aq)

Which of the following represents a process in which a species is reduced? A. Ca( s ) -->Ca2+( aq ) B. Hg( l ) -->Hg 2 + ( aq ) C. Fe 2+ ( aq ) -->Fe 3+ ( aq ) D. NO3 -- ( aq ) --> NO( g )

D. NO3 - ( aq ) --> NO( g )

Which of the following molecules has the largest dipole moment?

H2O

The electron-dot structure (Lewis structure) for which of the following molecules would have two unshared pairs of electrons on the central atom?

H2S

A 0.5 mol sample of He(g) and 0.5 mol of Ne(g) are placed separately in two 10.0 L rigid containers at 25⁰C. Each container has a pinhole opening. Which of the gases, He(g) or Ne(g), will escape faster through the pinhole and why?

He(g) will escape faster because the He(g) atoms are moving at a higher average speed than the Ne(g) atoms.

The complete photoelectron spectrum for an element is shown below. Which of the following observations would provide evidence that the spectrum is consistent with the atomic model of the element?

In its compounds, the element tends to form ions with a charge of +1.

A student places a piece of Iodine(s) in 50.0 mL of H2O(l), another piece of Iodine(s) of the same mass in 50.0 mL of C6H14(l), and shakes the mixtures. The results are shown below. What do the results indicate about the intermolecular interactions of the substances?

Iodine and C6H14 have similar intermolecular interactions, I2 and H2O do not.

A sample of a hard, solid binary compound at room temperature did not conduct electricity as a pure solid but became highly conductive when dissolved in water. Which of the following types of interactions is most likely between the particles in the substance?

Ionic bonds

Which of the following could be the identity of a white crystalline solid that exhibits the following properties? ** It melts at 357ºC ** It does not conduct electricity as a solid. ** It conducts electricity in an aqueous solution.

KNO3(s)

Based on the data in the tables below, which of the following statements provides the best prediction for the boiling point of LiCl?

LiCl will have a lower boiling point than LiF because the coulombic attractions are weaker in LiCl than in LiF.

The mass spectrum of a sample of a pure element is shown below. Based on the data, the peak at 26 amu represents an isotope of which of the following elements?

Mg with 14 neutrons

According to the information in the table below, a 1.00 g sample of which of the following contains the greatest mass of oxygen?

MgO

Which statement correctly compares what occurs when molecules absorb photons in the microwave region with what occurs when molecules absorb photons in the infrared region?

Microwave photons cause the molecules to increase their rotational energy states, whereas infrared photons cause molecules to increase their vibrational energy states.

A student obtains a sample of a pure solid compound. In addition to Avogadro's number, which of the following must the student know in order to determine how many molecules are in the sample?

Molar mass of the compound, mass of the sample

Which of the following contains 1 sigma σ(s) and two pi π (p) bonds?

N2

Which of the following molecules has the shortest bond length?

N2

Which statement best helps to explain the observation that NH3(l) boils at -28⁰C, whereas PH3(l) boils at -126⁰C?

NH3 has hydrogen bonding that is stronger than the dipole-dipole forces in PH3.

The effective nuclear charge experienced by the outermost electron of Na is different that the effective nuclear charge experienced by the outermost electron of Ne. This difference best accounts for which of the following?

Na has a lower first ionization energy than Ne.

Which of the following has a bond order of two?

O2

Based on Coulomb's law and the information in the table below, which of the following anions is most likely to have the strongest interactions with nearby water molecules in an aqueous solution?

S2-

The distribution of speeds of H2(g) molecules at 273 K and 1 atm is shown in the diagram above. Which of the following best shows the speed distribution of He(g) atoms under the same conditions of temperature and pressure? (Hydrogen is represented by the full line while Helium is represented by the dotted line.)

Option 1

Steel is an alloy consisting of Fe with a small amount of C. Elemental Cr can be added to steel to make the steel less likely to rust; Cr atoms react with oxygen in the air to form a nonreactive layer of chromium oxide on the surface of the steel, preventing the oxidation of underlying Fe atoms. A sample of steel-chromium alloy contains 15 percent Cr by mass. Which of the following diagrams best shows a particle-level view of a surface section and an interior section of the alloy represented below at the left? (The atomic radii of the atoms involved are given in the table below at the right.)

Option 2

The mass spectrum of the element Sb is most likely represented by which of the following?

Option 2 121 and 123 Atomic Mass

NH3 reacts with BF3 to form a single species. Which of the following structural diagrams is the most likely representation of the product of the reaction?

Option 4

Thymine and adenine form a base pair in the DNA molecule. These two bases can form a connection between two strands of DNA via two hydrogen bonds. Which of the following diagrams shows the correct representation of the hydrogen bonding (denoted by dashed lines) between thymine and adenine base pairs? (In each diagram thymine is shown at the left and adenine is shown at the right. The bases are attached to the backbone portion of the DNA strands.)

Option 4

Select the precipitation reaction

Pb2+(aq) + CrO42-(aq) = PbCrO4(s)

Equal volumes of 0.2M solutions of lead(II) nitrate and potassium bromide are combined to form lead(II) bromide as a yellow precipitate. Which of the following is the correct net ionic equation for the reaction?

Pb2+(aq)+2Br−(aq)→PbBr2(s)

To determine the percentage of water in a hydrated salt, at student heated a 1.2346g sample of the salt for 30 minutes; when cooled to room temperature, the sample weighted 1.1857g. After the sample was heated for an additional 10 minutes and again cooled to room temperature, the sample weighed 1.1632g. Which of the following should the student do next?

Reheat the sample until the mass is constant.

Consider atoms of the following elements. Assume that the atoms are in the ground state. The atom that contains exactly two unpaired electrons

S

CCl4, CO2, PCl3, PCl5, SF6 Which of the following does not describe any of these molecules?

Square planar

Which of the following best describes the type of bonding in a sample of CO2(s)?

Strong multiple covalent bonds, including pi bonds,

Atmospheric methane is a potent greenhouse gas. The concentration of methane in Earth's atmosphere in 1998, expressed as a mole fraction, was 1745 nmol/mol (parts per billion, ppb). By 2008, however, global methane levels, which had stayed mostly flat since 1998, had risen to 1800 nmol/mol. Which of the following best describes the type of bonding in a sample of CH4(g)?

Strong single covalent bonds

Which of the following is true about the reaction 2A--> B + C which is first order in A and first order overall?

The concentration of A will decrease exponentially.

A student places a sample of a pure metal in a crucible and heats it strongly in air. Data from the experiment are given in the table above. The final mass was determined after the sample was cooled to room temperature. Which of the following statements related to the experiment is correct?

The mass of the sample increased, so a chemical change occurred when bonds formed between the metal and another substance.

Diagram 1 below shows equimolar samples of two gases inside a container fitted with a removable barrier placed so that each gas occupies the same volume. The barrier is carefully removed as the temperature is held constant. Diagram 2 above shows the gases soon after the barrier was removed. Which statement describes the changes to the initial pressure of each gas and the final partial pressure of each gas in the mixture, and indicates the final total pressure?

The partial pressure of each gas in the mixture is half its initial pressure; the final total pressure is half the sum of the initial pressures of the two gases.

When a sample of oxygen in a closed container (kept at a constant volume) is heated until its absolute temperature is doubled, which of the following is also doubled?

The pressure of the gas

Four different liquid compounds in flasks at 20⁰C are represented above. The table below identifies the compounds. Flask C shows the most particles in the vapor phase. Which of the following is not shown in the model but best helps to explain why flask C must contain pentane?

The strength of the intermolecular forces between the particles in the liquids

The table below shows the first ionization energy and atomic radius of several elements. Which of the following best helps to explain the deviations of the first ionization energy of oxygen from the overall trend?

There is repulsion between paired electrons in oxygen's 2p orbitals.

The student uses visible spectrophotometry to determine the concentration of CoCl2(aq) in a sample solution. First the student prepares a set of CoCl2(aq) of known concentrations. Then the student uses a spectrophotometer to determine the absorbance of each of the standard solutions at a wavelength of 510nm and constructs a standard curve. Finally, the student determines the absorbance of the sample of unknown concentration. The student made the standard curve below. Which of the following most likely caused the error in the point the student plotted at 0.050 M Co2+ (aq)?

There was distilled water in the cuvette when the student put the standard solution in it.

In a paper chromatography experiment, a sample of a pigment is separated into two components, X and Y, as shown in the figure below. The surface of the paper is polar. What can be concluded about X and Y based on the experimental results?

X is more polar than Y.

Based on the ionization energies of element X given in the table above, which of the following is must likely the empirical formula of an oxide of element X?

X2O3

For the reaction whose rate law is rate = k[X] , a plot of which of the following is a straight line?

ln [X] versus time

What is the hybridization of the carbon atoms in a molecule of ethyne, represented below? H-C=_ C-H

sp

The geometry of the SO3 molecule is best described as

trigonal planar