AP Chemistry Midterm - Past MC

Missing Questions: (unit 1: #9,10) (unit 2: #2,3,10)

In which of the following compounds is the mass ratio of chromium closest to oxygen closest to 1.6 to 1.0

CrO2

Styrene, a compound used to make Styrofoam cups (MM = 104 g/mol) contains 92.3% C abd 7.75% H. What is styrene’s molecular formula?

C8H8

Copper (II) sulfate pentahydrate, CuSO4\*5H20 (molar mass: 250 g/mol) can be dehydrated by repeated heating in a crucible. Which value is closest to the percentage mass of water lost from the total mass of salt in the crucible when the crucible undergoes repetitive heating’s until a constant is reached?

36%

A measured mass of an unreactive metal was dropped into a small graduated cylinder half filled with water. The following measurements were made.

Mass of Metal = 19.611 grams

Volume of water before addition of metal = 12.4 ml

Volume of water after addition of metal = 14.9

The density of the metal should be reported as:

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7\.8 grams per mL

The first five ionization energies of a second-element are listed in the table below. Which of the following correctly identifies the element and best explains the data in the table?



Ionization Energy (kj/mol)

First: 801

Second: 2430

Third: 3660

Fourth: 25000

Fifth: 32820

B, because it has three valence electrons

The atoms of an element, X, has the electron configuration below. What compound would element X most likely form with magnesium (Mg)?

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X: 1s^2 2s^2 2p^6 3s^2 3p^3

Mg3X2

Which electron configuration represents an atom in an excited state? (^ = arrow)

1s___ 2s_^_

The element in photoelectron spectroscopy graph, below, is most likely

N

In which balance and block arrangement below, can you be sure the lighter colored block is more dense?

a

Chlorine has two naturally occuring isotopes with masses of 34.969 amu. Which mass spectrum is most likely to correspond to a naturally occuring sample of chlorine?

b

Which of the following correctly lists the compounds in order of increasing lattice energy?

CsI < KCL < CaO < MgO

Copper atoms and zinc atoms have the same atomic radius, 135 picometers. Based on this information, which of the following diagrams best represents an alloy containing only copper and zinc attoms?

b

Which of the following is the most favorable Lewis dot structure for SOCl2, considering formal charge? \**lines drawn around atoms represent a lone pair of electrons**

b

(Refer to energy diagram)

What is the approximate bond length between the two atoms?

0\.140 nm

(Refer to energy diagram)

What is the bond energy (bond strength) of the bond?

330 J

What is the electron geometry of H20?

Tetrahedral

What is the hybridization of one of the carbon atoms in C2H4?

sp^2

What is the molecular geometry of BrI3?

T-Shaped

The potential energy as a function of internuclear distance for three diatomic molecules X2, Y2, and Z2, is shown in the graph to the right. Based on the data in the graph, which of the following correctly identifies the diatomic molecules X2, Y2, and Z2?

X2 Y2 Z2

H2 N2 O2

Which of the following Lewis Structures of C3H7Br below, represents an isomer of the compound that has the Lewis structure shown above?

a

Which of the following has bonds arranged in order of decreasing polarity?

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Sb -- I > Sb--Te > Sb--Cl

O--N> O--S > O--Te

H--I > H--Br > H--F

H--F > N--F> F--F

H--F > N--F> F--F

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

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SO2

NO

NH3

CF4

CF4

A 50.0 mg sample of calcium bromide, CaBr2, (molar mass 200g) is dissolved in enough water to produce 200 mL of solution. What is the molarity of calcium bromide in a 50 mL sample of this solution?

0\.00125 M

The boiling points of the elements helium, neon, argon, krypton, and xenon increase in that order. Choose all of the following statements that best account for this increase?

The (london) dispersion forces increase.

Which gas listed below has an average atomic or molecular speed closest to that of N2 molecules at 0 C and 1 atm?

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CO

NO

O2

Ne

CO

Equal masses of three different ideal gases X, Y, and Z, are mixed in a sealed rigid container. If the temperature of the system remains constant, which of the following statements of the partial pressure of gas X is correct?

It depends on the molecular masses of X, Y, and Z.

Two flexible containers for gases are at the same temperature and pressure. One holds 0.59 gram of hydrogen and the other holds 8.0 grams of oxygen. Which of the following statements regarding these gas samples is FALSE?

The average speed of the hydrogen molecules is the same as the average speed of the oxygen molecules.

A 2L sample of N2(g) and a 6L sample of Ar(g), each originally at 1 atm and 0 C, are combined in a 2L tank. If the temperature is held constant, what is the total pressure in the 2L tank?

4 atm

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

butane < acetone < 1-propanal

The diagram represent the absorption spectrum for a pure molecular substance. Which of the following correctly indicates the type of transition observed for the substance in each of the regions of the absorption spectrum?

region X - electron transition

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region Y - molecular vibration

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region Z - molecular rotation

Which of the following is LEAST soluable in water?

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KMnO4

(NH4)2SO4

Na3PO4

BaCO3

BaCO3

When 100 ml of 1.0 M AlCl3 is mixed with 100 ml of 1.0 M Na2CrO4, a yellow precipitate forms and \[CrO4^2-\] becomes negligibly small. Which of the following is a correct listing of the ions remaining in solution in order of increasing concentration?

\[Al^3+\] < \[Na+\] < \[Cl-\]

An aqueous solution contains 0.6 mol KCl and 1.20 mol NH4Cl. What is the minimum number of moles of Pb(No3)2 that must be added to precipitate all of the chloride ions?

0\.90 mol

The unbalanced products of the combustion of sucrose (C12H22O11) are..

CO2 abd H2O

Predict the balanced products of the following reaction: Chlorine gas is bubbled through a solution of potassium bromide.

2KCl + Br2

A strong acid is added to a strong base. What is the net ionic equation of the reaction?

H+(aq) + OH- (aq) → H2O (l)

How many electrons appear in the following half-reaction when it is balanced?

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12H+ + 2IO3- → I2 + 6H20

10e- on the left

In which of the following species does the sulfur have the same oxidization number as it does in H2SO4?

SO2Cl2

*_H+ + _*NO3- + *Mg → Mg+2 +* NH+4 +_H20

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When the equation above is balanced with lowest whole number coefficients, the coefficient for H+ is:

10

2H20 + 4MnO4- + 3CLO2- → 4MnO2 + 3 ClO4- + 4OH-

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Which compund in the reaction above contains the element that is reduced?

MnO4-