1

AP Chemistry Midterm Review Chapters 2 thru 5

1. Cr2O72− + 6 I − + 14 H + → 2 Cr3+ (aq) + 3 I2 + 7H2O

Which of the following statements regarding the reaction shown above is NOT true?

(A) The oxidation number of chromium changes from +6 to +3.

(B) The oxidation number of iodine changes from – 1 to 0 .

(C) The oxidation number of hydrogen changes from +1 to 0.

(D) The oxidation number of oxygen remains the same.

(E) Iodine is oxidized and chromium is reduced.

2. CaCO3(s) → CaO (s) + CO2(g)

A sample of pure CaCO3 was heated and decomposed according to the reaction given above. If 21 grams of

CaO were produced by the reaction that gives a 75% yield, what was the initial mass of CaCO3?

(A) 14 grams

(B) 25 grams

(C) 42 grams

(D) 50 grams

(E) 84 grams

3. _2__CuFeS2 + _4__O2 → ___Cu2S + _2__FeO + _3__SO2

When the reaction above is balanced, what is the coefficient for O2 if all the coefficients are reduced to the

lowest whole number.

(A) 2

(B) 3

(C) 4

(D) 6

(E) 8

4. A student added 1 liter of a 1.0 M KCl solution to 1 liter of a 1.0 M Pb(NO3)2 solution. A lead chloride

precipitate formed and nearly all of the lead ions disappeared from the solution. Which of the following lists

the ions remaining in solution in order of decreasing concentration?

(A) NO3− > K+ > Pb2+

(B) NO3− > Pb2+ > K+

(C) K+ > Pb2+ > NO3− Nitrate will be 2moles/2 liters = 1.0 M

(D) K+ > NO3− > Pb2+ Potassium will be 1.0 mol/ 2 L = 0.5 M

(E) Pb2+ > NO3− > K+ Lead will be 0.50 mol/2 L = 0.25 M

Section

4.9

Section

3.9

Section

3.8

Section

4.3

2

5. 2 MnO4 – + 5 SO3

2 – + 6 H+ → 2 Mn2+ + 5 SO42 – + 3 H2O

Which of the following statements is true regarding the reaction given above?

(A) MnO4− has been oxidized (not true – it’s reduced from +7 to +2)

(B) H+ acts as the oxidizing agent (not true – the oxidation number does not change)

(C) SO3− is reduced (no we already established that MnO4

- is reduced)

(D) SO32− acts as the reducing agent

(E) MnO4− acts as the reducing agent (not true – it is the oxidizing agent because it’s reduced)

6. Which one of the following has its name and chemical formula correctly matched?

(A) HIO3 hydroiodic acid

(B) HIO hypoiodous acid

(C) HI iodic acid

(D) NaIO3 sodium iodide

(E) CuIO2 cupric iodate

7. An ion containing only oxygen and chlorine is 31% oxygen by mass. What is its empirical formula?

(A) ClO ─

(B) ClO2 ─

(C) ClO3 ─

(D) ClO4 ─

(E) ClO5 ─

8. Consider three 1-L flasks at STP. Flask A contains NH3 gas, flask B contains NO2 gas, and flask C contains

N2 gas. Which flask contains the largest number of molecules?

(A) flask A

(B) flask B

(C) flask C

(D) all have the same number of molecules

9. Which flask do the molecules have the highest average velocity? Depends on mass

(A) flask A

(B) flask B

(C) flask C

(D) all have the same velocity

10. Which of the following is a strong base?

I. HClO2

II. NH3

III. LiOH

IV. Mg(OH)2 Magnesium hydroxide is not very soluble. It has limited solubility, meaning not very much is going to

dissolve. You get low concentrations of hydroxides. It will act like a weak base in that it doesn't generate a high concentration of hydroxides (A) I only

(B) II only

(C) III only

(D) III and IV

(E) IV only

Section

4.9

Section

2.8

Section

3.6

Section

5.1

Section

5.1

Section

4.3

3

11. Which of the following has 3 significant figures?

I. 1990 m

II. 0.02 m

III. 0.0560 m

IV. 1.70 x 102 m

(A) I only

(B) I, II, and IV

(C) III only

(D) I, III, and IV

(E) none of the above

12. Which of the following regarding atomic theory is NOT true?

(A) Dalton was the first person to suggest the existence of atoms.

(B) Rutherford's experiments with alpha particle scattering led to the conclusion that positive

charge was concentrated in an atom's nucleus.

(C) Democritus first suggested the existence of tiny indivisible particles.

(D) Millikan's oil drop experiment led to the calculation of the charge on an electron.

(E) Thomson's cathode ray experiments confirmed the existence of the electron.

13. Elements in group 7A on the periodic table are known as the

(A) halogens

(B) alkali metals

(C) alkaline earth metals

(D) iron family

(E) noble gases

14. The correct name for HClO4 is

(A) hydrochloric acid

(B) hypochloric acid

(C) perchloric acid

(D) chloric acid

(E) hydrogen chlorate

15. The 6 strong acids ___.

(A) are weak electrolytes

(B) dissociate 100% ONE HUNDRED PERCENT!

(C) are insoluble in aqueous solution

(D) are ionic

(E) would not conduct an electric current in aqueous solution

Section

1.5

Sections

2.3

Section

2.5

Section

2.8

Section

4.2

4

16. Water and a salt are always the products of a(n) ___ reaction.

(A) redox

(B) displacement * metathesis = double replacement

(C) combustion

(D) neutralization

(E) metathesis, or hydrolysis (if it reacts, soluble salts dissociate into their ions.)

17. What is/are the spectator ion(s) in the reaction between Pb (s) and HCl(aq)?

(A) Cl─ and H+

(B) H+ and Pb2+ (single replacement yields PbCl2 (s) and H2)

(C) Pb2+ and Cl ─

(D) H+ only

(E) there are no spectator ions

18. Which of the following compounds is 100% dissociated in aqueous solution?

(A) Mg(OH)2

(B) Sc2S3

(C) CuCO3

(D) BaSO4

(E) HNO3 Strong acid

19. In which of the following compounds has a percent composition of 30% N and 70 % O?

(A) N2O5

(B) NO

(C) N2O3

(D) N2O

(E) NO2

20. The following data were gathered in an experiment to determine the density of a sample of an unknown

substance.

Mass of the sample 7.5 grams

Volume of the sample 2.5 mL

The density of the sample should be reported as

(A) 3 g/ cm3

(B) 3.0 g/ cm3

(C) 3 g/ cm3

(D) 0.3 g/ cm3

(E) 0.33 g/ cm3

Section

4.8

Section

4.6

Section

4.2

Section

3.6

Section

1.8

5

21. Which of the following unbalanced equations would have the net ionic equation of

H+ + OH – → H2O? (Do not worry about balancing.)

I. HNO3(aq) + KOH (aq) →

II. Fe(s) + Ni(NO3)2(aq) →

III. HCl (aq) + Na2S (aq) →

IV. Mg(s) + HCl(aq) →

(A) I, II, III, and IV

(B) III only

(C) I and IV only

(D) IV only

(E) I only

22. The name of the following compound, C2H6, is

(A) ethane

(B) tetrane

(C) butane

(D) propane

(E) pentane

23. NaCH3COO Ba(NO3)2 KCl

Aqueous solutions of equal concentration of the three compounds listed above are prepared in 3 separate

containers. A precipitate in one of the containers could be expected when a solution of ___ is added.

(A) SO42─ ions –will form a ppt with barium nitrate

(B) Cu2+ ions

(C) OH─ ions

(D) nitric acid

(E) potassium chlorate

24. Use the following reactions to determine the activity series for the halogens. Do not look at the periodic

table until AFTER you have tried this.

Br2(aq) + 2 NaI(aq) → 2 NaBr (aq) + I2(aq)

Cl2(aq) + 2 NaBr(aq) → 2 NaCl(aq) + Br2(aq)

(A) Br < Cl < I

(B) I < Br < Cl

(C) Cl < Br < I

(D) I < Cl < Br

(E) Cl < I < Br

Section

4.6

Section

22.1

Section

4.5

Section

4.9

6

25. On the periodic table, which group typically has an oxidation number of ─2 ?

(A) 5A

(B) 6A

(C) 7A

(D) 3A

(E) 2A

26. Which of the following best represents the net ionic equation for the reaction of solid sodium carbonate

with an aqueous solution of magnesium chloride solution?

(A) Na2CO3 + MgCl2 → MgCO3 + 2 NaCl

(B) Na2CO3 + Mg2+ → MgCO3 + 2 Na+

(C) CO32─ + Mg2+ → MgCO3

(D) 2 Na+ + 2 Cl– → 2 NaCl

(E) There is NO net-ionic equation b/c everything is soluble!

27. When 80.0 mL of a 0.40 M NaI solution is combined with 20.0 mL of a 0.30 M CaI2 solution, what will be

the molar concentration of I− ions in the solution?

(A) 0.70 M

(B) 0.44 M

(C) 0.38 M

(D) 0.35 M

(E) 0.10 M

28. A beaker contains 150.0 mL of a 0.20 M Pb(NO3)2 solution. If 50.0 mL of a 0.20 M solution of MgCl2 is

added to the beaker, what will be the final concentration of Pb2+ ions in the solution?

(A) 0.20 M

(B) 0.10 M

(C) 0.050 M

(D) 0.025 M

(E) 0.012 M

29. How much 0.1-molar NaOH solution must be added to 100 milliliters of a 0.2-molar H2SO4 solution in

order to neutralize all of the hydrogen ions in H2SO4

(A) 100 mL

(B) 200 mL

(C) 300 mL

(D) 400 mL

(E) 500 mL

30. How much water must be added to a 50.0 mL solution of 0.60 M HNO3 to produce a 0.40 M solution of

HNO3?

(A) 25 mL

(B) 33 mL

(C) 50 mL

(D) 67 mL

(E) 78 mL

Sections

4.9

Section

4.6

Section

4.3

Section

4.3

Section

4.8

Section

4.3

7

AP Chem-1 Midterm Review Chp 1 - 4

Follow ALL math work rules! Circle your final answers. Work must be neat, easy to follow and flow in a logical progression towards the answer. No credit will be given for

correct answers with incomprehensible, little, or no supporting work.

2 KMnO4(aq) + 16 HCl(aq) → 2 KCl(aq) + 2MnCl2(aq) + 5 Cl2(g) + 8 H2O(l)

1. In a solution KMnO4 was mixed with a solution of HCl as shown above.

(a) Which ELEMENT has been oxidized in this reaction? Chlorine

(b) Which ELEMENT has been reduced in this experiment? Manganese

(c) What mass, in grams, of permanganate ion must the student use to completely react 5.0 g of

chloride ion? 2.1 g

Section

4.4

Section

4.4

Section

3.6

8

2. Answer the following question about a pure compound that contains only carbon, hydrogen, and oxygen.

A compound is composed of only C, H, and O. Combustion of a 0.519-g sample of the

compounds yields 1.24 g of CO2 and 0.255 g of H2O. What is the empirical formula of the

compound.

(a) Calculate the mass in grams of carbon in the original sample. 0.338 g

(b) Calculate the mass in grams of hydrogen in the original sample. 0.0285 g

(c) Calculate the mass in grams of oxygen in the original sample. 0.153 g

(d) Determine the empirical formula for the compound. C3H3O

Section

3.5

Section

3.5

Section

3.5

Section

3.5

9

3. (a) Write the complete balanced equation, including phases of matter, for combustion

of decane, C10H22 (l).

2 C10H22 (l) + 31 O2 (g) 20 CO2 (g) + 22 H2O (g)

(b) Decane has a density of 0.703 g/ mL at 20oC. Calculate the total number of moles of

product formed when 2-L of decane measured at 20.0oC is completely combusted. 208 mol

Section

3.2

Section

3.6

10

4. 16 grams of methane gas reacts with 16 grams of oxygen in a combustion reaction.

(a) Write a balanced chemical equation (least whole-number ratio) for this reaction. Include

phases of matter.

CH4 + 2 O2 CO2 + 2 H2O

(b) Identify the limiting reactant, if any, in this reaction. Prove your answer mathematically.

The limiting reactant is oxygen.

(c) Determine the mass, in grams, of the excess reactant after completion of the reaction.

12 grams of CH4 are excess

Sections

3.1, 3.2

Section

3.7

Section

3.5

11

5. A beaker contains exactly 200 milliliters of a solution of hydrochloric acid solution of unknown

concentration.

(a) The solution was titrated with 0.400- molar NaOH solution and the equivalence point was

reached when 100- milliliters of NaOH was added.

i. Write a balanced chemical equation for this neutralization reaction. Don’t forget phases

of matter!

HCl (aq) + NaOH (aq) NaCl + H2O

ii. Calculate the moles of hydrochloric acid in the original 200 mL of solution.

0.400 M NaOH x 100 mL = 40 mmol NaOH = 40 mmol HCl or 0.040 mol

iii. Calculate the concentration of the hydrochloric acid in the original 200 mL of solution.

40 mmol/200 mL = 0.200 M HCl

iv. What is the concentration of chlorine ion in the solution at the equivalence point reached

in (a) (i)?

0.133 M - Chlorine is a spectator ion so the moles do not change (0.040 mol) but the

volume does change from 200 mL to 300 mL at the equivalence point.

Section

3.5

Sections

4.5, 4.6

Sections

4.5, 4.6

Sections

4.5, 4.6

12

END