Third Quarter Review Sheet Answers

REACTIONS:

1. Define and explain how precipitates are formed?

Identify the type of reaction for 2-6

2. C3H5(NO3)3 CO2 + N2 + H2O + O2decomposition

3. Zn + 2HCl  ZnCl2 + H2single replacement

4. Pb(NO3)3 + K2CrO4 PbCrO4 + KNO3double replacement

5. 2C6H6 + 15O2 12CO2 + 6H2Ocombustion

6. 3H2 + N2 2NH3synthesis

Balance the equations for questions 7 through 11

7. 2HgO + Cl22HgCl + O2

8. C2H4 + 3O22CO2 + 2H2Ocombustion

9. Ca(OH)2 + 2HNO3 Ca(NO3)2 +2 H2O

10. P4 + 5O2 P4O10

11. 4FeS2 + 11O22Fe2O3 + 8SO2 2FeS2 + 5.5 O2 Fe2O3 + 4SO2 can’t have half multiply by 2

12. Which of the following reaction will take place?

  1. Mg + LiOH No Reaction
  2. 6Na + Al2(SO3)3Yes, 3Na2SO3 + 2Al
  3. Hg + CuS No Reaction
  4. None of the above

13. What happens to Na2SO4 when mixed into water?

It dissolves

14. Which of the following will not break up upon being mixed into water?

a. NaCl b. NO2c. Mg(NO3)2d. FeCl3

15. Which of the following will break up upon being mixed in water?

a. CaCO3b. AgClc. Ba(OH)2d. MgO

16. Write the net ionic equation for the following pair of reactants?

AgNO3 + NaOHAgOH(s) + NaNO3

Ag+ + OH-  AgOH(s)

  1. `What are the spectator ions in the previous reaction?

Na+ and NO3

18. Write the net ionic equation for the following pair of reactants?

Fe(NO3)2(aq)+ MgS (aq) FeS(s) + Mg(NO3)2

Fe+2 + S-2 FeS

19. Suppose we were doing an experiment in which we were trying to predict precipitates formed in double replacement reactions. We find that many of these reactions yield precipitates yet one of them, between NaCl and Mg(NO3)2, does not. What is the correct explanation for this?

both products are soluble in water

20. The following data table was generated by a student by mixing two ionic compounds together and then writing down the results. The student’s data is listed below:

Na2SO4 / MgCl2
Ba(NO3)2 / White precipitate / No precipitate
NaOH / No precipitate / White precipitate

Based on the student’s data above, which of the following substances is one of the

precipitates formed in the lab above?

a. NaClb. Mg(NO3)2c. Ba(OH)2d. BaSO4

21. In redox reactions oxidation is always coupled with what? reduction

22. Define the terms oxidation and reduction. LEO the lion goes GER

23. What three substances can be added freely to a redox reaction occurring in an acidic solution in order to balance a half reaction? Water(H2O) H+ and e-

24. What is meant by “half reaction” in reference to a redox reaction?

25. In a redox reaction the number of electrons in the oxidation half reaction must equal the number in the reduction half

26. What is the oxidation number of “Cr” in MgCr2O7? +6

27. What is the oxidation number of “P” in PO43-? +5

28. Identify what is oxidized in the following reaction.

+1 –2 +1+5-2 0 +2-2 +1-2

3H2S + 2HNO3 3S + 2NO + 4H2O

reduced

oxidized3e- +4H+ +NO3-NO + 2H2O

29. Identify what is reduced in the reaction from the previous problem. Nitrogen

30. Identify the oxidizing agent in the following reaction.

KMnO4 + HCl  MnCl2 + Cl2 + H2O + KCl

Just Mn is OK

31. Balance the following 1/2 reaction.

5e- + 8H++ MnO41- Mn2+ +4H2O

-5+ +7=+2+2

32. What half reaction is shown above? Reduction

33. Which of the following correctly balances the following 1/2 reaction?

2Cl1- Cl2 +2e-

34. What half reaction is shown above? oxidation

35. What is the net ionic equation for the following

Pb(ClO3)2 (aq)+ NaI (aq) PbI2 (s) + NaClO3

Pb+2 + I-  PbI2 (s)

MOLE:

  1. Avagadro’s number tells us what?

Particles in a mole.

2. Define empirical formula. Smallest whole number ratio

3. How many atoms are in a sample of an element whose mass in grams is numerically equal to its atomic mass? 6.02 X1023

4. What kind of substance is represented by a formula unit? Ionic compound

5. The molar mass of individual elements is generally expressed in which unit? g/mol

6. How many ions of Cu+2 are there in one formula unit of Cu3(PO3)2? 3

7. The mass of each element in a compound compared to the entire mass of the compound is called what? Percent composition

  1. The percent composition of magnesium chloride, MgCl2, is?

24.3 + 2(35.5) = 95.3 24.3/95.3 = 25% 71/95.3 = 75%

  1. What is the empirical formula for a compound whose molecular formula is C2Cl6?

CCl3

10. What is the only possible molecular formula, from the choices below, for a compound whose empirical formula is CH?

a. C2Hc. CH2

b. C2H2d. need more info

11. If the empirical formula of a compound is found to be CH2, which of the following values are possible molecular molar masses?

a. 21.04b. 46.76c. 12.01d. 70.15

12. Which of the following correctly describes how to convert 250g of Ca(OH)2 into formula units? Convert 250g of Ca(OH)2 into moles by dividing by the molar mass and then divide that by 6.02x1023.

  1. Convert 250g of Ca(OH)2 into moles by dividing by the molar mass and then multiply that by 6.02x1023.
  1. Convert 250g of Ca(OH)2 into moles by dividing by the molar mass and then divide that by 6.02x1023. Once you have that number multiply by 3.
  1. Convert 250g of Ca(OH)2 into moles by dividing by the molar mass and then multiply that by 6.02x1023. Once you have that number multiply by 3.

13. Calculate the molar mass of LiOH. 24g/mol

14. How many F- ions are present in 2.50 moles of BaF2? 2.50 X 6.02X1023 = 1.5 X1024 X 2 = 3.0 X1024

15. If you have 2.87x1024 formula units of MgCl2, how many moles do you have? 4.77 mol

16. What is the volume of 16g of O2? 16/32 = .5 mol X 22.4 L = 11.2 L

17. If you have 348L of H2O vapor, how many moles do you have? 348/22.4 = 15.5 moles

18. If you have 26.4g of gold, how much of a mole do you have? 26.4g /197(molar mass) = .13 mol

19. What is the empirical formula of a compound that is 46.62% Na, 20.95% P, and 32.43% O?

46.62/23 = 2/.68 = 3 20.95/31 = .68/.68=1 32.43/16 = 2/.68 =3 Na3PO3

20. If a compound has an empirical of CH2O, and a molecular mass of 120g, what is the molecular formula? C4H8O4

21. What is the representative particle for P4O10? molecule

22. What is the representative particle for BaCl2? FU formula unit

23. How many grams of Mg are present in 150.0g of Mg3(PO4)2? 3(24.3) + 2(31) + 8(16) = 262.9 27.7 % Mg X 150 g = 41.6 grams

24. Define the term mole with respect to mass, volume, and representative particles.