Mr. Kilduff AP Chem Exam 2 (Avengence of the Fribble)

2 MnO4-(aq) + 10 Br-(aq) + 16 H+(aq) → 2 Mn2+(aq) + 5 Br2(aq) + 8 H2O(l) How many electrons are transferred in the reaction represented by the balanced equation above? A 2 B 4 C 5 D 8 E 10

E

What is the oxidation of oxygen in bromine in aluminum bromide is A)5+ B)2+ C)5+ D)1+ E)3+

E

Which of the following best describes the process represented above that takes place when NH3 is added to water?

It is an acid-base reaction in which a proton is exchanged from H2O to NH3.

HC2H3O2(aq)+OH−(aq)→C2H3O2−(aq)+H2O(l)A student carried out a titration using HC2H3O2(aq) and NaOH(aq). The net ionic equation for the neutralization reaction that occurs during the titration is represented above. The NaOH(aq) was added from a buret to the HC2H3O2(aq) in a flask. The equivalence point was reached when a total of 20.0mL of NaOH(aq) had been added to the flask. How does the amount of HC2H3O2(aq) in the flask after the addition of 5.0mL of NaOH(aq) compare to the amount of HC2H3O2(aq) in the flask after the addition of 1.0mL of NaOH(aq), and what is the reason for this result?

it is less because more HC2H3O2(aq) reacted with the base.

Check Practice exam open ended

1 precipitation and 1 redox

A 0.50g sample of Mg(s) was placed in a solution of HCl(aq), where it reacted completely. Which of the following equations best represents the reacting species in the reaction described above? A Mg(s)+2H+(aq)→Mg2+(aq)+H2(g) B Mg(s)+HCl(aq)→MgCl2(aq)+H2(g) C Mg(s)+2HCl(aq)→MgCl2(s)+2H+(aq) D Mg(s)+2HCl(aq)→Mg2+(aq)+Cl2(g)+H2(g)

A

C6H5COOH(aq)+NaOH(aq)→C6H5COONa(aq)+H2O(l)Which of the following identifies a conjugate acid-base pair in the reaction represented above?

Acid C6H5COOHC6 Conjugate baseH5COO−

A 0.35 g sample of Li(s) is placed in an Erlenmeyer flask containing 100 mL of water at 25°C. A balloon is placed over the mouth of the flask to collect the hydrogen gas that is generated. After all of the Li(s) has reacted with H2O(l), the solution in the flask is added to a clean, dry buret and used to titrate an aqueous solution of a monoprotic acid. The pH curve for this titration is shown in the diagram below Which of the following is the balanced net-ionic equation for the reaction between Li(s) and water? A 2 Li(s) + 2 H+(aq) + 2 OH−(aq) → 2 Li+(aq) + 2 OH−(aq) + H2(g) B 2 Li(s) + 2 H2O(l) → 2 Li+(aq) + 2 OH−(aq) + H2(g) C 2 Li(s) + 2 H2O(l) → 2 LiOH(s) + H2(g) D 2 Li(s) + 2 H2O(l) → 2 LiH(s) + H2(g)

B

A group of students was asked to recover Cu(s) from a blue-green aqueous solution containing an unknown concentration of Cu2+(aq) . The students took a 100.0 mL sample of the solution and added an excess of 1.0 M Na3PO4(aq), causing the Cu2+(aq) to precipitate as Cu3(PO4)2(s), as shown in step 1 below. Step 1 3Cu(2 pos) + 2Na3PO4 —> Cu3(PO4)2 + 6Na+ The Cu3(PO4)2(s) was filtered, dried, and weighed. Then the Cu3(PO4)2(s) was dissolved in a 3.0 M HCl(aq) solution, as shown in step 2 below. Step 2 Cu3(PO4)2 + 6HCl —> 3CuCl2 + 2H3PO4 The students added a strip of Zn(s) to the solution to recover the Cu(s), as shown in step 3 below. Step 3 CuCl2 + Zn —> Cu + ZnCl2 Finally, the Cu(s) was filtered, dried, and weighed. If 3.8 g of Cu3(PO4)2(s) was recovered from step 1, what was the approximate [Cu2+] in the original solution? (The molar mass of Cu3(PO4)2 is 381 g/mol.) A 0.10 M B 0.30 M C 1.0 M D 3.0 M

B

An experiment is performed to measure the mass percent of CaCO3(s) in eggshells. Five different samples of CaCO3(s) of known mass react with an excess of 2.0MHCl(aq) in identical sealed, rigid reaction vessels. The pressure of the gas produced is measured with a pressure gauge attached to the reaction vessel. Since the reaction is exothermic, the reaction system is cooled to its original temperature before the pressure is recorded. The experimental data are used to create the calibration line below. The experiment is repeated with an eggshell sample, and the experimental data are recorded in the table below. Mass of eggshell sample - 0.200g Pressure prior to rxn - 0.800atm Pressure at completion of reaction - 0.870atm Which of the following equations best represents the species that react and the species that are produced when CaCO3(s) and HCl(aq) are combined? A 2H+(aq)+CaCO3(s)→Ca2+(aq)+CO32−(aq)+H2(g) B 2H+(aq)+CaCO3(s)→Ca2+(aq)+H2O(l)+CO2(g) C 2H+(aq)+CaCO3(s)→Ca2+(aq)+2OH−(aq)+CO(g) D 2HCl(aq)+CaCO3(s)→Ca2+(aq)+H2O(l)+CO2(g)+2Cl−(aq)

B

HCl(aq)+NaOH(aq)→NaCl(aq)+H2O(l) A student had two dilute, colorless solutions, HCl(aq) and NaOH(aq), which were at the same temperature. The student combined the solutions, and the reaction represented above occurred. Which of the following results would be evidence that a chemical reaction took place? A The resulting solution is colorless. B The temperature of the reaction mixture increases. C The total volume of the mixture is approximately equal to the sum of the initial volumes. D The resulting solution conducts electricity.

B

Which equation represents a neutralization reaction? (All aqueous) A) Na+ + Cl- —>NaCl B) HCl + NH3 —> NH4Cl C) Pb2+ + 2Cl- —> PbCl2 D) BaI2 + MgSO4 —> BaSO4 + MgI2

B

A 1.0 L sample of an aqueous solution contains 0.10 mol of NaCl and 0.10 mol of CaCl2. What is the minimum number of moles of AgNO3 that must be added to the solution in order to precipitate all of the Cl- as AgCl(s) ? (Assume that AgCl is insoluble.) A 0.10 mol B 0.20 mol C 0.30 mol D 0.40 mol E 0.60 mol

C

A 20. mL sample of 0.50 M HC2H3O2(aq) is titrated with 0.50 M NaOH(aq). Which of the following best represents the species that react and the species produced in the reaction? A H+(aq) + OH−(aq) → H2O(l) B H+(aq) + C2H3O2−(aq) + Na+(aq) + OH−(aq) → H2O(l) + NaC2H3O2(aq) C HC2H3O2(aq) + OH-(aq) → C2H3O2-(aq) + H2O(l) D HC2H3O2(aq) + NaOH(aq) → H2O(I) + Na+(aq) + C2H3O2-(aq)

C

A solution is known to contain Ca2+, Fe2+, and Hg2 2+ ions. What is the best way to separate calcium ions from the others in solution? A) Adding a dilute acetic acid (aq) solution B) Adding a dilute perchloric acid (aq) solution C) Adding a dilute hydroflouric (aq) solution D) Adding a Dilute nitric acid (aq) solution E) Adding a Dilute sodium hydroxide (aq)

C

A solution of MgCl2 has a chloride ion concentration of 0.300M, what is the concentration of MgCl2? A. 0.300M B. 0.200M C. 0.150M D. 0.100M E. 0.600M

C

The entire ionic equation for the hydrolysis of Na2CO3 is A) H2O + Na+ —> NaOH + H+ B) H2O + CO3 2- —> H2CO3 + O 2- C) H2O + CO3 2- —> HCO3 - + OH- D)H2O +2Na + —> NaOH + H +

C

Which of the following causes a precipitate to form when Mg2+ is added, but not when Zn2+ is added? A) S2- B)Cl- C)SO4 2- D)CO3 2- E)NO3-

C

Solution: NaI; Observation: no precipitate Solution: Na2SO4; Observation: precipitate Solution: NaOH; Observation: no precipitate A solution containing an unknown cation was added to three solutions and the above observations were recorded. The unknown cation is A)Ca 2+ B)Pb 2+ C)Ag + D)Sr 2+

D

Which of the following ions could be used to separate the Cl-(aq) from SO4 2- by precipitation? A)NH4+ B)Pb2+ C)K+ D)Ca2+ E)Al3+

D

Which of the following titrations would have an equivalence point of less than pH 7? A) NaOH and HNO3 B) Ba(OH)2 and H2SO$ C) KOH and CH3COOH D) NH3 and HCL E) BaSO4 and KOH

D