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AP Chemistry Medium practice

15 questions

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Medium practice

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Question 1

An element's fifth ionization energy is dramatically larger than its fourth. What does this indicate about the element's electron configuration?

A.The element is in Group 4 of the periodic table.B.The element is in Group 5 of the periodic table.C.The element has five valence electrons.D.The fourth and fifth electrons occupy the same orbital.

Question 2

A photoelectron spectrum of an unknown element shows peaks at binding energies of approximately 2470, 190, 99, and 11 eV. Based on the pattern of peaks and the known PES of the elements, which element is this most likely to be?

A.CarbonB.NeonC.MagnesiumD.Silicon

Question 3

Adding an inert gas to a gaseous equilibrium system at constant volume has what effect on the equilibrium position?

A.Shifts toward the side with more moles of gas.B.Shifts toward the side with fewer moles of gas.C.No shift; the equilibrium position is unchanged.D.Shifts forward to consume the extra pressure.

Question 4

A reaction has the energy profile shown below (described): the reactants are at a higher energy than the products, and there is a single energy maximum (transition state) between them. The activation energy for the forward reaction is $80 kJ/mol$ and for the reverse reaction is $120 kJ/mol$ . What is $Δ H$ for the forward reaction?

- 40 kJ/mol

+ 40 kJ/mol

+ 200 kJ/mol

- 120 kJ/mol

Question 5

Rank these liquids in order of increasing viscosity: ethanol ( $C_{2} H_{5} OH$ ), glycerol ( $C_{3} H_{5} (OH)_{3}$ ), and hexane ( $C_{6} H_{14}$ ).

A.Hexane

<

Ethanol

<

GlycerolB.Ethanol

<

Hexane

<

GlycerolC.Glycerol

<

Ethanol

<

HexaneD.Hexane

<

Glycerol

<

Ethanol

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Question 6

The average bond enthalpy of an O=O double bond is $498 kJ/mol$ and that of an O–H bond is $464 kJ/mol$ . Using bond enthalpies, estimate $Δ H$ for:

$2 H_{2} (g) + O_{2} (g) \to 2 H_{2} O (g)$

( $D (H - H) = 436 kJ/mol$ )

- 478 kJ

- 484 kJ

+ 484 kJ

- 928 kJ

Question 7

Using the following standard enthalpies of formation, calculate $Δ H^{\circ}$ for $C H_{4} (g) + 2 O_{2} (g) \to C O_{2} (g) + 2 H_{2} O (l)$ :

$Δ H_{f}^{\circ} [C H_{4} (g)] = - 74.8 kJ/mol$

$Δ H_{f}^{\circ} [C O_{2} (g)] = - 393.5 kJ/mol$

$Δ H_{f}^{\circ} [H_{2} O (l)] = - 285.8 kJ/mol$

- 604.5 kJ/mol

- 890.3 kJ/mol

+ 890.3 kJ/mol

- 965.1 kJ/mol

Question 8

For the equilibrium $A (g) ⇌ 2 B (g)$ , an ICE table gives the following initial and change rows:

	A	B
Initial	$0.600 M$	$0$
Change	$- x$	$+ 2 x$
Equilibrium	$0.600 - x$	$2 x$

If $K_{c} = 0.040$ , what is the equilibrium concentration of A?

0.550 M

0.600 M

0.200 M

0.0500 M

Question 9

Which of the following species has a trigonal planar molecular geometry?

N H_{3}

S O_{3}

PC l_{3}

Cl F_{3}

Question 10

The rate of decomposition of $N_{2} O_{5}$ is measured at two temperatures:

Temperature	Rate constant $k$
$25° C$	$3.0 \times 1 0^{- 5} s^{- 1}$
$45° C$	$1.2 \times 1 0^{- 4} s^{- 1}$

Which statement about this data is correct?

A.The reaction rate doubles for every

10° C

increase because that is a chemistry rule.B.The rate constant increases by a factor of 4 over a 20°C range, consistent with Arrhenius behavior.C.The rate constant doubles when temperature is doubled, so the reaction is second order in temperature.D.The rate constant is independent of temperature for a first-order reaction.

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Question 11

At constant temperature, the pressure of a fixed amount of gas is increased from $1.00 atm$ to $4.00 atm$ . By what factor does the volume change?

A.Increases by a factor of 4B.Decreases by a factor of 4C.Decreases by a factor of 2D.Remains unchanged

Question 12

The relationship between $K_{c}$ and $K_{p}$ for a gas-phase equilibrium is $K_{p} = K_{c} (R T)^{Δ n}$ , where $Δ n$ is the change in moles of gas. For the reaction $2 S O_{3} (g) ⇌ 2 S O_{2} (g) + O_{2} (g)$ , $Δ n =$ ?

- 1

+ 1

+ 2

0

Question 13

What is the electron-pair geometry and molecular geometry of $S F_{4}$ ?

A.Tetrahedral; tetrahedralB.Trigonal bipyramidal; trigonal bipyramidalC.Trigonal bipyramidal; see-sawD.Octahedral; square planar

Question 14

During the titration of a weak acid (HA) with a strong base (NaOH), the half-equivalence point is reached when half the acid has been neutralized. At the half-equivalence point:

pH = 7.0

for all weak acids.B.

pH = p K_{a}

of the weak acid.C.

[A^{-}] = 0

because no conjugate base has formed yet.D.

pH

is highest at this point during the titration.

Question 15

A proposed mechanism for a reaction is:

Step 1 (slow): $N O_{2} + N O_{2} \to N O_{3} + NO$

Step 2 (fast): $N O_{3} + CO \to N O_{2} + C O_{2}$

What is the overall reaction and the predicted rate law?

A.Overall:

N O_{2} + CO \to NO + C O_{2}

; rate

= k [N O_{2}] [CO]

B.Overall:

N O_{2} + CO \to NO + C O_{2}

; rate

= k [N O_{2}]^{2}

C.Overall:

2 N O_{2} + CO \to N O_{3} + NO + C O_{2}

; rate

= k [N O_{2}]^{2} [CO]

D.Overall:

N O_{2} + CO \to NO + C O_{2}

; rate

= k [N O_{3}] [CO]

AP Chemistry Medium practice — Free with Answer Explanations | Test Practice Hub