AP Chem Exam Multiple Choice

How many protons neutrons and electrons are in an 56/26 Fe atom?

26 protons, 30 neutrons and 26 electrons

A student is trying to determine the heat of reaction for the acid-base neutralization reaction represented above. The student uses 0.50 M NaOH and 0.50 M HCl solutions. Which of the following situations, by itself, would most likely result in the LEAST error in the calculated value of the heat of reaction A. The thermometer was incorrectly calibrated and read 0.5 C degree too high during the procedure B. The volume of the acid solution added to the calorimeter was actually 1.0 mL less than what was recorded C.The calorimeter was poorly insulated, and some heat escaped to the atmosphere during the procedure D. The actual molarity of the base solution was 0.53 M but was recorded as 0.50 M E. The final temperature of the mixture was taken before the contents of the calorimeter had reached thermal equilibrium

A

A. H2O B. NH3 C. BH3 D. CH4 E. SiH4 Which has two lone pairs of electrons

A

Gases generated in a chemical reaction are sometimes collected by the displacement of water, as shown above. Which of the following gases can be quantitatively collected by this method? A. H2 B. CO2 C. HCl D. SO2 E. NH3

A

If 50 mL of 1.0 M NaOH is diluted with distilled water to a volume of 2.0 L, the concentration of the resulting solution is A. 0.0025 M B. 0.050 M C. 0.10 M D. 0.50 M E. 1.0 M

A

Which of the following lists Mg, P and Cl in order of increasing atomic radius? A. Cl < P < Mg B. Cl < Mg < P C. Mg < P < Cl D. Mg < Cl < P E. P < Cl < Mg

A

Which of the following molecules contains exactly three sigma bonds and two pi bonds A. C₂H₂ B. CO₂ C. HCN D. SO₃ E. N₂

A

2 Nh3 → 3 H2 + n2 ∆H + 92 kj/mol According to the information above what is the standard enthalpy of formation ∆H for NH3 at 298K A. -92 B. -46 C. 46 D. 92 E. 184

B

A molecular solid coexists with its liquid phase at its melting point. The solid-liquid mixture is heated, but the temperature does not change while the solid is melting. The best explanation for this phenomenon is that the heat absorbed by the mixture A. is lost to the surroundings very quickly B. is used in overcoming the intermolecular attractions in the solid C. is used in breaking the bonds within the molecules of the solid D. causes the nonbonding electrons in the molecules to move to lower energy levels E. causes evaporation of the liquid, which has a cooling effect

B

A. H2O B. NH3 C. BH3 D. CH4 E. SiH4 Which has a trigonal-pyramidal molecular geometry​

B

An unknown acid is dissolved in 25mL of water and titrated with 0.1000 M NaOH. The results are shown in the titration curve above. Which of the following could be the unknown acid? A. pKa = 2.6 B. pKa = 3.8 C. pKa = 4.9 D. pKa = 7.5 E. pKa = 9.3

B

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 A. Li B. Ba C. Al D. Cl E. Ne

B

Hone the equation above is balanced and the coefficients are reduced to lowest whole number terms, what is the coefficient of H2O A. 1 B. 2 C. 3 D. 4 E. 5

B

Resonance is most commonly used to describe the bonding in molecules of which of the following A. CO₂ B. O₃ C. H₂O D. CH₄ E. SF₆

B

The reaction represented above is observed to proceed spontaneously to the right in aqeous solution. In this system the strongest base is A. So4² B.CO₃² C. H₂O D. HCO³ E. HSO⁴

B

Which of the following is NOT an accepted name for the formula given A. CH₃OH.. methanol B. CuO .. copper (i) oxide C. FeCl₃ ... iron (iii) chloride D. H₂SO₄ ... sulfuric acid E. SrCO₃ ... strontium carbonate

B

The reaction between a Broasted-Lowry acid and a Bronsted-Lowry Base

B (C2H3O2- + H3O+ --> HC2H3O2 + H2O)

Which flask contains the smallest number of moles of gas

B (High temp, low pressure)

In which flask do the molecules have the greatest average speed

B (High temp, low pressure)

A 0.10 M solution of a weak monoprotic acid has a pH equal to 4.0. The ionization constant ka of the acid is A. 1 x 10^-3 B. 1 x 10^-4 C. 1 x 10^-7 D. 1 x 10^-8 E. 1 x 10^-9

C

A 2L sample of N2 and a 1 L sample of Ar each originally at 1 atm and O C are combined in a 1L tank. if the temperature is held constant, what is the total pressure of the gases in the tank? A. 1 atm B. 2 atm C. 3 atm D. 4 atm E. 5 atm

C

A student prepares a solution by dissolving 60.00g of glucose in enough distilled water to make 250.0mL of solution. The molarity of the solution should be reported as A. 12.01 M B. 12.0 M C. 1.332 M D. 1.33 M E. 1.3 M

C

A. H2O B. NH3 C. BH3 D. CH4 E. SiH4 Which has a central atoms with less than an octet of electrons

C

A. H2O B. NH3 C. BH3 D. CH4 E. SiH4 Which is predicted to have the largest bond angle

C

The role of a catalyst in a chemical reaction is to A. decrease the amount of reactants that must be used B. lower the activation energy for the reaction C. supply the activation energy required for the reaction to proceed D. increase the amounts of products formed at equilibrium E. increase the entropy change for the reaction

C

What is the empirical formula of an oxide of chromium that is 48 percent oxygen by mass A. CrO B. CrO2 C. CrO3 D. Cr2O E. Cr2O3

C

Which of the following is an isomer of CH₃OCH₃ A. CH₃CH₃ B. CH₃COOH C. CH₃CH₂OH D. CH₃CH₂CH₃ E. CH₃CH₂OCH₂CH₃

C

Which of the following substances is a strong electrolyte when dissolved in water A. sucrose B. ethanol C. sodium nitrate D. acetic acid E. ammonia

C

Which flask contains the sample with the greatest density

C (Highest pressure)

According to the standard reduction potentials given above, what is the standard cell potential for the reaction represented below? A. -1.74 V B. -0.86 V C. 1.74 V D. 2.46 V E. 4.06 V

D

For an experiment, a student needs 100 mL of 0.4220 M NaCl. If the student starts with NaCl and distilled water, which of the following pieces of laboratory glassware should the student use to prepare the solution A. 25 mL volumetric pipet B. 100 mL Erlenmeyer flask C. 100 mL graudated cylinder D. 100 mL volumetric flask E. 1 L beaker

D

H2 + F2→ 2HF In the reaction represented above, what mass of HF is produced by the reaction of 3.0 x 10^23 molecules of H2 with excess F2 A. 1 g B. 4 g C. 10 g D. 20 g E. 40 g

D

In an insulated cup of negligible heat capacity, 50 g of water at 40 C mixed with 30 g of water at 20 C. The final temperature of the mixture is closest to A. 22 C B. 27 C C. 30 C D. 33 C E. 38 C

D

Permanganate and oxalate ions react in an acidified solution according to the balanced equation above. How many moles of Co2 are produced when 20 mL of acidified 0.20 M KmnO₄ solution is added to 50 mL of 0.10 M Na2C2O4 A. 0.0040 B. 0.0050 C. 0.0090 D. 0.010 E. 0.020

D

A 0.20 mol sample of MgCl2 and a 0.10 mol sample of KCl are dissolved in water and diluted to 500 mL. What is the concentration of Cl- in the solution? A. 0.15 B. 0.30 C. 0.50 D. 0.60 E. 1.0

E

C2H4 is reduced by H2 in the presence of a solid platinum catalyst, as represented by the equation above. Factors that could affect the rate of the reaction include which of the following I. Changes in the partial pressure of H2 II. Changes in the particles size of the platinum catalyst III. Changes in the temperature of the reaction system A. III only B. I and II C. I and III D. II and III E. I, II and III

E

For which of the following reaction mixtures at equlibrium would reducing the volume of the container at constant temperature cause the equilibrium to shift towards the products? A. SrCO3 ⇌ SrO + Co2 B. C + Co2 ⇌ 2 CO C. Co + H2O ⇌ Co2 + H2 D. PCl5 ⇌ Pcl3 + Cl2 E. 2 No2 ⇌ N2O4

E

Which of the following statements is true for the equilibrium vapor pressure of a liquid in a closed system? A. It remains constant when the temperature increases B. It decreases to half its original value if the volume of the gas phase is doubled C. It increases to twice its original value if the volume of the liquid phase is doubled D. It decreases to half its original value if the surface area of the liquid is reduced by one half E. it is independent of the volume of the vapor phase

E

The reaction in which a single species is both oxidized and reduced

E (2 H2O --> O2 + 2H2O)

Which contains an element in a +1 oxidation state

E (Cu2O)

For the reaction represented above at 25 C, what are the sings of delta H, S, G

∆H : - ∆S : - ∆G: -

KHP is used as a primary standard for determining the concentration of a solution of NaOh by titration. If the KHP has not been dried before weighing, the calculated molarity of the NaOH would be A. higher than the actual value since water is included in the mass B. higher than the actual value, since the presence of water requires a larger volume of titrant C. lower than the actual value, since NaOH absorbs water D. unaffected, since KHP is a strong acid E. unaffected, since water is routinely added before titration

A

C3H8 + 5O2 --> 3 Co2 + 4 H2O In the reaction represented above, what is the total number of moles of reactants consumed when 1.00 mole of Co2 is produced? A. 0.33 mol B. 1.33 mol C. 1.50 mol D. 2.00 mol E. 6.00 mol

D

High solubility of an ionic solid in water is favored by which of the following conditions I. The existence of strong ionic attractions in the crystal lattice II. The formation of strong ion-dipole attractions III. An increase in entropy upon dissolving A. I B. I and II C. I and III D. II and III E. I, II, and III

D

When a 3.22 g sample of an unknown hydrate of sodium sukfate, Na2So4 * x H2O is heated, H2O is driven off. The mass of the anhydrous Na2SO4 that remains is 1.42. The value of x in the hydrate is A. 0.0013 B. 1.8 C. 6.0 D. 10 E. 20

D

Which of the following molecules contains polar covalent bonds but is a nonpolar molecule? A. Ch3Cl B. CH2Cl2 C. NH3 D. CCl4 E. N2

D

Which of the following substances has the greatest solubility in C5H12 at 1 atm A. SiO2 B. NaCl C. H2O D. CCl4 E. NH3

D

If the oxygen isotope ²⁰O has a half-life of 15 seconds, what fraction of a sample of pure ²⁰O remains after 1.0 minute A. 1/2 B. 1/4 C. 7/30 D. 1/8 E. 1/16

E

N2O5 ⇌ 2No2 + 1/2 O2 The equilibrium constant for the gas phase reaction above is 95 ar 25 C. What is the value of the equilibrium constant for the following reaction at 25C O2 + 4NO2 ⇌ 2 N2O5 A. (95)² B. 95 C. (95)¹/² D. 1/95 E. 1/(95)²

E

The percentage of silver in a solid sample is determined gravimetrically by converting the solver Ag and precipiatating it as silver chloride. Failure to do which of the following could cause errors in the analysis I. Account for the mass of the weighing paper when determining the mass of the sample II. Measure the temperature during the precipitation reaction III. Wash the precipitate IV. Heat the AgCl precipitate to constant mass A. I only B. I and II C. I and IV D. II and III E. I, II and IV

E

When 4.00 mol of each of X and Y are placed in a 1.00 L vessel and allowed to react at constant temperature according to the equation above, 6.00 mol of Z is produced. What is the value of the equilibrium constant Kc A. 3 B. 6 C. 8 D. 16 E. 36

E

Which of the following elements has the largest first ionization energy A. Li B. Be C. B D. C E. N

E

Which of the following is the electron configuration of an excited atom that is likely to emit a quantum of energy? A. 1s²2s²2p⁶3s²3p¹ B. 1s²2s²2p⁶3s²3p⁵ C. 1s²2s²2p⁶3s² D. 1s²2s²2p⁶3s¹ E. 1s²2s²2p⁶3s¹3p¹

E

Which of the following lists the substances F₂, HCL and HF in order of increasing boiling point A. HF < HCl < F2 B. HF < F2 <HCl C. HCl < F2 < HF D. HCl < HF < F2 E. F2 < HCl < HF

E

Which of the following process involves the greatest increase in entropy A. So3 + H2 → SO2 + H2O B. N2 + 3H2 → 2NH3 C. Ag + Cl- →AgCl D. C2H2 + 2H2 → C2H6 E. MgSo3 →MgO + So2

E