ap unit 4 worksheet answers - Ms. Jensen Chemistry

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Name______ANSWER KEY________________________________period________ap chemistry unit 4 worksheet. 1. The molecules BF3 and SO3 are both ...
Name__________________________________________________period____________AP chemistry Unit 4 worksheet 1.

The formation of glucose, C6H12O6 produces ethyl alcohol, C2H5OH and CO2: C6H12O6  2C2H5OH + 2CO2 a. How many moles of carbon dioxide are produced when 0.300 mol of glucose reacts? 0.600 mol b. How many grams of glucose are needed to form 2.00 g of methyl alcohol? 3.91 g c. How many grams of carbon dioxide form when 2.00 g of methyl alcohol are produced? 1.91 g

2.

Aluminum sulfide reacts with water to form aluminum hydroxide and hydrogen sulfide. a. Write the balanced equation for this reaction. Al2S3 + 6H2O  2Al(OH)3 +3 H2S b. How many grams of aluminum hydroxide are formed from 10.5 g of aluminum sulfide? 10.9 g c. What is the percent yield if the mass obtained of aluminum hydroxide was 3.4 g? 32% Automotive air bags inflate when sodium azide, NaN3, rapidly decomposes. 1 L = 0.035 ft3 2NaN3 (s)  2 Na (s) + 3 N2 (g) a. How many moles of nitrogen gas are produced by the decomposition of 1.50 moles of sodium azide? 2.25 mol b. How many grams of NaN3 are required to form 5.00 g of nitrogen gas? 7.74 g c. How many grams of NaN3 are required to produce 10.0 ft3 of nitrogen gas if the gas has a density of 1.25 g/L? 548 g Why are the amounts of the product formed in a reaction determined only by the amount of limiting reaction? The limiting reactant regulates the amount of products because it is completely used up during the reaction; no more products can be made when one reactant is unavailable.

3.

4.

5.

6.

The fizz produced when an alka-seltzer tablet is dissolved in water is due to the reaction between sodium bicarbonate and citric acid, H3C6H5O7 3NaHCO3 + H3C6H5O7  3 CO2 + 3 H2O + Na3C6H5O7 In a certain experiment 1.00 g of sodium bicarbonate and 1.00 g of citric acid are allowed to react. a. Which reactant is the limiting reactant? NaHCO3 b.

How many grams of carbon dioxide form? 0.524 g

c.

How much of the excess reactant remains after the limiting reactant is completely consumed? 0.238 g

Solutions of sodium carbonate and silver nitrate react to form solid silver carbonate and sodium nitrate. A solution containing 5.00 g of sodium carbonate is mixed with one containing 5.00 g of silver nitrate. After the reaction is complete, the solutions are evaporated to dryness, leaving a mixture of salts. How many grams of sodium carbonate, silver nitrate, silver carbonate, and sodium nitrate are present after the reaction is complete? 3.46 g of sodium carbonate, 0 g of silver nitrate, 4.00 g of silver carbonate, and 2.47 g sodium nitrate

7.

Write a balanced reaction for each of the following. a. Lithium metal is burned in air 4Li + O2  2Li2O b. Aluminum metal is added to a solution of copper (II) chloride 2Al + 3CuCl2  2AlCl3 + 3Cu c.

Manganese (II) nitrate solution is mixed with sodium hydroxide solution Mn(NO3)2 + 2NaOH  2NaNO3 + Mn(OH)2

d.

The hydrocarbon hexane (C6H14) is burned in excess oxygen 2C6H14 + 19O2  12 CO2 + 14H2O

a.

Silver nitrate solution is added to potassium chromate solution and a precipitate forms 2AgNO3 + K2CrO4  Ag2CrO4 + 2KNO3

b.

Hydrogen peroxide decomposes H2O2 2H2O + O2

c.

Solid calcium carbonate is reacted with sulfuric acid CaCO3 + H2SO4  CaSO4 + H2O + CO2

d.

magnesium sulfate solution and potassium hydroxide solution are mixed together MgSO4 + 2KOH  Mg(OH)2 + K2SO4 Strontium hydroxide is mixed with hydrofluoric acid Sr(OH)2 + 2HF  2H2O + SrF2

e.

f.

Powdered strontium oxide is added to distilled water SrO + H2O  Sr(OH)2

g.

Chlorine gas is bubbled through a solution of potassium bromide Cl2 +2 KBr 2KCl + Br2

h.

Potassium sulfide is reacted with nitric acid K2S + 2HNO3  2KNO3 + H2S

i.

Solid lithium is added to distilled water 2Li + 2H2O  LiOH + H2

8.

When methyl alcohol, CH3OH is dissolved in water, a nonconducting solution results. When acetic acid dissolves in water, the solution is weakly conducting. Describe what happens upon dissolution in the two cases, and account for the different results. Methyl alcohol does not dissociate or ionize. There are no ions moving around. Acetic acid is a weak acid is it partially ionizes and a small amount of ions move around to conduct electricity.

9.

Show how the following dissociates or ionizes upon dissolving in water a. Zinc chloride b. nitric acid c. iron (II) sulfate d. ammonium carbonate 2+ a. ZnCl2  Zn + 2Cl b. HNO3  H+ + NO3c. FeSO4  Fe2+ + SO42d. (NH4)2CO3  2NH4+ + CO32-

10. Formic acid, HCHO2, is a weak electrolyte. What solute particles are present in an aqueous solution of this compound? (draw a picture of it in water) HCHO2, H+, CHO211. Hydrobromic acid is a strong electrolyte. What solute particles are present in an aqueous solution of this compound? (draw a picture of it in water) H+ and Br12. Will precipitation occur when the following are mixed? If so, name the precipitate a. Na2CO3 and AgNO3 b. NaOH and K2SO4 c. FeSO4 and Pb(NO3)2 Ag2CO3 no precipitate lead sulfate 13. What are the spectator ions when the following react a. Pb(NO3)2 + Na2SO4 b. CuBr2 + NaOH c. AgNO3 + KI Sodium and nitrate Sodium and bromide Potassium, nitrate 14. Separate samples of a solution of an unknown ionic compound are treated with dilute AgNO 3, Pb(NO3)2 and BaCl2. Precipitates form in all three cases. Which of the following anions could be the anion of the unknown salt? Br -, CO32-, NO3Carbonate 15. What is the difference between a. A monoprotic acid and a diprotic acid Donates one proton; donates two protons b. A weak acid and a strong acid Partially ionizes; completely ionizes c. An acid and a base Has Hydrogen; has hydroxide 16. Label as a strong, weak, or nonelectrolyte a. HCl b. NaF c. CO2 Strong strong non

d. HF weak

17. Classify each as a strong or weak acid or base a. HClO4 b. HClO2 c. LiOH Strong acid weak acid strong base

d. NH3 weak base

e. NaOH strong

f. Mg(OH)2 weak

e. H2S weak acid

g. C2H5OH non

f. Al(OH)3 weak base

18. Write a balanced net ionic reaction for the following a. b. c. d. e. f. g.

h.

Potassium hydroxide solution is added to a solution of aluminum nitrate 3OH- + Al3+  Al(OH)3 Sulfur dioxide gas is bubbled into distilled water. SO2 + H2O  H2SO3 A strip of magnesium metal is heated strongly in pure nitrogen gas Mg + N2  Mg3N2 A solution of nickel (II) chloride is added to a solution of sodium sulfide and a precipitate forms. Ni2+ + S2-  NiS Sodium metal is added to water Na + H2O  Na+ + OH- + H2 A strip of copper is immersed in nitric acid Cu + 2H+  H2 + Cu2+ Concentrated hydrochloric acid is added to solid manganese (II) sulfide (chlorides are soluble unless with silver, mercury, or lead) 2H+ + MnS  Mn2+ + H2S A solution of potassium phosphate and zinc nitrate are mixed and a precipitate is made PO43- + Zn2+  Zn3(PO4)2

Mass of KI tablet Mass of thoroughly dried filter paper Mass of filter paper + precipitate after first drying Mass of filter paper + precipitate after second drying Mass of filter paper + precipitate after third drying

0.425 g 1.462 g 1.775 g 1.699 g 1.698 g

19. A student is given the task of determining the I  content of tablets that contain KI and an inert, water-soluble sugar as a filler. A tablet is dissolved in 50.0 mL of distilled water, and an excess of Pb(NO3)2 (aq) is added to the solution. A yellow precipitate forms, which is then filtered, washed, and dried. The data from the experiment are shown in the table above. (a) For the chemical reaction that occurs when the precipitate forms, (i) write a balanced, net-ionic equation for the reaction, and

Pb2+ + 2 I  PbI2 (ii) explain why the reaction is best represented by a net-ionic equation.

The net-ionic equation shows the formation of the PbI2 (s) from Pb2+(aq) and I  (aq) ions, omitting the non-reacting species (spectator ions), K+ (aq) and NO3  (aq). (b) Explain the purpose of drying and weighing the filter paper with the precipitate three times.

The filter paper and precipitate must be dried several times (to a constant mass) to ensure that all the water has been driven off. (c) In the filtrate solution, is [K+ ] greater than, less than, or equal to [NO3  ] ? Justify your answer.

[K+ ] is less than [NO3  ] because the source of the NO3 , the Pb(NO3 )2 (aq), was added in excess. (d) Calculate the number of moles of precipitate that is produced in the experiment.

5.12 x 10-4 mol (e) Calculate the mass percent of I in the tablet. 30.6% (f) In another trial, the student dissolves a tablet in 55.0 mL of water instead of 50.0 mL of water. Predict whether the experimentally determined mass percent of I will be greater than, less than, or equal to the amount calculated in part (e). Justify your answer.

The mass percent of I  will be the same. Pb2+(aq) was added in excess, ensuring that essentially no I  remained in solution. The additional water is removed by filtration and drying, leaving the same mass of dried precipitate. (g) The student only has access to one KI tablet and a balance that can measure to the nearest 0.01 g. Will the student be able to determine the mass of precipitate produced to three significant figures? Justify your answer.

No. If masses can be measured to 0.01 g, then the mass of the dry AgI(s) precipitate (which is less than 1 g) will be known to only two significant figures. Review: 20. After doing a calculation the display shows the number 3760.289 on the calculator. If the answer is supposed to have three significant figures, the correct way to display the answer would be: a. 3.76 x 102 b. 3760. c. 376 d. 376 x 101 e. 3.76 x 103

21. How many protons, neutrons, and electrons are in the following atoms a. 40 Ar b. 55Mn c. 65Zn d. phosphorus-32 18, 22, 18 25,30,25 30,35,30 15, 17, 15

e. 235 U 92, 143, 92

22. What are basic properties of metals, metalloids, and nonmetals? Metals are conductors, malleable, shiny luster Metalloids- semiconductors Nonmetals- nonconductors, brittle as a solid, 23. A student is assigned the task of determining the mass percent of silver in an alloy of copper and silver by dissolving a sample of the alloy in excess nitric acid and then precipitating the silver as AgCl. The the student pours 25 mL of the HNO3 into a beaker and adds a 0.6489 g sample of the alloy. After the sample completely reacts with the acid, some saturated NaCl(aq) is added to the beaker, resulting in the formation of an AgCl precipitate. Additional NaCl(aq) is added until no more precipitate is observed to form. The precipitate is filtered, dried, and weighed to constant mass in a filter crucible. The data are shown in the table below. Mass of sample of copper - silver alloy Mass of dry filter crucible Mass of filter crucible and precipitate (1st weighing) Mass of filter crucible and precipitate (2nd weighing) Mass of filter crucible and precipitate (3rd weighing)

0.6489 g 28.7210 g 29.3587 g 29.2599 g 29.2598 g

a.)

Calculate the number of moles of AgCl precipitate collected. 0.003760 mol

b.)

Calculate the mass percent of silver in the alloy of copper and silver. 63.7 %

24. According to the information in the table below, a 1.00 g sample of which of the following contains the greatest mass of oxygen? Compound Molar mass (grams) Na2O 62.0 MgO 40.3 K2O 94.2 CaO 56.1 a. Na2O

b. MgO

c. K2O

d. CaO

25. An empty crucible has a mass of 12.770 grams. The crucible and hydrate have a mass of 13.454 grams. After heating, the crucible and anhydrous salt have a mass of 13.010 grams. What is the formula of this hydrate of MgSO 4 ?H2O? MgSO4 · 12H2O 26. What is the molar mass of cholesterol if 0.00105 mol weighs 0.406 g? 386.6 g/mol 27. What is the molecular geometry of SF4? Is this a polar or nonpolar molecule? See saw; polar 28. Find the molecular geometry, hybrid orbitals used, bond order, polarity and formal charges of NO2-? Bent, sp2, 1.5, polar, O:-1 N:0, O:0