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AP Chemistry Hard practice

15 questions

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Hard practice

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Question 1

Which of the following correctly ranks the species by increasing atomic/ionic radius?

$C l^{-}, Cl, N a^{+}, Na$

N a^{+} < C l^{-} < Na < Cl

N a^{+} < Na < C l^{-} < Cl

N a^{+} < Cl < Na < C l^{-}

Cl < N a^{+} < Na < C l^{-}

Question 2

A mixture of gas A (molar mass $4 g/mol$ ) and gas B (molar mass $64 g/mol$ ) effuses through a small orifice. According to Graham's Law, how much faster does gas A effuse compared to gas B?

A.4 times fasterB.16 times fasterC.

4 = 2

times fasterD.8 times faster

Question 3

A 5.00-L container holds $0.500 mol$ of an ideal gas at $27° C$ . What is the pressure in atm? ( $R = 0.0821 L \cdot atm/ (mol \cdot K)$ )

0.274 atm

2.46 atm

4.93 atm

0.492 atm

Question 4

Removing a product from a reaction system at equilibrium will:

A.Shift the equilibrium to the left (toward reactants) to replenish what was removed.B.Shift the equilibrium to the right (toward products) to partially restore the product concentration.C.Have no effect because

K_{c}

does not change.D.Decrease

K_{c}

to account for the lower product concentration.

Question 5

According to the kinetic molecular theory of gases, what happens to the average kinetic energy of gas molecules when temperature is doubled (from 300 K to 600 K)?

A.It doubles.B.It quadruples.C.It increases by

2

.D.It remains the same; only pressure changes.

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Question 6

A buffer contains $0.300 M$ $N H_{3}$ and $0.200 M$ $N H_{4} Cl$ . What is the pH? ( $K_{b} (N H_{3}) = 1.8 \times 1 0^{- 5}$ ; $p K_{a} (N H_{4}^{+}) = 9.26$ )

9.44

9.08

4.56

9.26

Question 7

For the second-order integrated rate law $\frac{1}{[ A ] _{t}} = k t + \frac{1}{[ A ] _{0}}$ , if $[A]_{0} = 0.500 M$ and $k = 0.0400 M^{- 1} \cdot s^{- 1}$ , what is $[A]$ after $100 s$ ?

0.167 M

0.250 M

0.100 M

0.333 M

Question 8

In a balanced redox equation in acidic solution, $Mn O_{4}^{-}$ is reduced to $M n^{2 +}$ while $F e^{2 +}$ is oxidized to $F e^{3 +}$ . How many $F e^{2 +}$ ions are required to reduce one $Mn O_{4}^{-}$ ?

2

3

5

7

Question 9

How many grams of copper are deposited when a current of $2.00 A$ passes through a $CuS O_{4}$ solution for $1.00 hour$ ? ( $M (Cu) = 63.5 g/mol$ ; $F = 96, 485 C/mol$ ; Cu deposits as Cu $^{2 +} + 2 e^{-} \to Cu$ )

2.37 g

4.74 g

0.75 g

9.48 g

Question 10

Spectral lines in the visible emission spectrum of hydrogen are produced when an electron transitions from a higher energy level to:

Select the statement that is both correct and explains the underlying mechanism.

n = 1

, releasing ultraviolet photons equal in energy to the transition.B.

n = 2

, releasing a photon whose energy equals the difference in quantized energy levels.C.

n = 3

, releasing infrared radiation.D.

n = 2

, absorbing a photon to move to a lower energy state.

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Question 11

In a bomb calorimeter experiment, $1.00 g$ of glucose ( $M = 180 g/mol$ ) causes a temperature rise of $2.00° C$ in a calorimeter with heat capacity $C_{cal} = 7.78 kJ/°C$ . What is the molar heat of combustion of glucose?

- 15.6 kJ/g

- 2800 kJ/mol

- 5330 kJ/mol

- 156 kJ/mol

Question 12

Consider a combustion reaction: $C_{3} H_{8} (g) + 5 O_{2} (g) \to 3 C O_{2} (g) + 4 H_{2} O (g)$ . If $44.0 g$ of propane ( $M = 44.1 g/mol$ ) reacts with $128 g$ of $O_{2}$ ( $M = 32.0 g/mol$ ), which is the limiting reagent?

C_{3} H_{8}

, because its mass is smaller.B.

O_{2}

, because 5 moles are needed per mole of propane but only 4 moles of O

_{2}

are available.C.

C_{3} H_{8}

, because the mole ratio requires more propane than available.D.Neither; both are present in stoichiometric amounts.

Question 13

For the dissolution of calcium fluoride, $Ca F_{2} (s) ⇌ C a^{2 +} (aq) + 2 F^{-} (aq)$ , the $K_{s p} = 3.9 \times 1 0^{- 11}$ . What is the molar solubility of $Ca F_{2}$ ?

2.1 \times 1 0^{- 4} M

3.9 \times 1 0^{- 11} M

6.2 \times 1 0^{- 6} M

1.3 \times 1 0^{- 4} M

Question 14

Which of the following describes a precipitation reaction?

HCl (aq) + NaOH (aq) \to NaCl (aq) + H_{2} O (l)

CaC l_{2} (aq) + N a_{2} S O_{4} (aq) \to CaS O_{4} (s) + 2 NaCl (aq)

Zn (s) + CuS O_{4} (aq) \to ZnS O_{4} (aq) + Cu (s)

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

Question 15

Given:

(1) $C (s) + O_{2} (g) \to C O_{2} (g)$ , $Δ H_{1} = - 393.5 kJ$

(2) $2 CO (g) + O_{2} (g) \to 2 C O_{2} (g)$ , $Δ H_{2} = - 566.0 kJ$

Use Hess's Law to find $Δ H$ for: $2 C (s) + O_{2} (g) \to 2 CO (g)$

- 959.5 kJ

- 221.0 kJ

+ 221.0 kJ

- 172.5 kJ

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