Unit 4 Chem Assignments + test
C 12
. . . C10H12O4S(s) + . . . O2(g) → . . . CO2(g) + . . . SO2(g) + . . . H2O(g) When the equation above is balanced and all coefficients are reduced to their lowest whole-number terms, the coefficient for O2(g) is A 6 B 7 C 12 D 14 E 28
D chemical change because covalent bonds are broken and new covalent bonds are formed
2 H2O2(l) → 2 H2O(l) + O2(g) The exothermic process represented above is best classified as a A physical change because a new phase appears in the products B physical change because O2(g) that was dissolved comes out of solution C chemical change because entropy increases as the process proceeds D chemical change because covalent bonds are broken and new covalent bonds are formed
A 9.0 g
2 N2H4(g) + N2O4(g) → 3 N2(g) + 4 H2O(g) When 8.0 g of N2H4 (32 g mol-1) and 92 g of N2O4 (92 g mol-1) are mixed together and react according to the equation above, what is the maximum mass of H2O that can be produced? A 9.0 g B 18 g C 36 g D 72 g E 144 g
(b) 67%
2KClO3 -> 2KCl + 3O2 What is the percentage yield of O2 if 12.3 g of KClO3 (molar mass 123 g) is decomposed to produce 3.2 g of O2 (molar mass 32) according to the equation above? (a) 100% (b) 67% (c) 50% (d) 33% (e) 10%
A It is an oxidation-reduction reaction, and MgMg is oxidized.
2Mg(s)+SiCl4(l)→2MgCl2(s)+Si(s)2Mg(s)+SiCl4(l)→2MgCl2(s)+Si(s) Which of the following statements about the reaction represented above is correct? A It is an oxidation-reduction reaction, and MgMg is oxidized. B It is an oxidation-reduction reaction, and electrons are transferred from SiCl4SiCl4 to MgMg C It is an oxidation-reduction reaction, and the oxidation number of ClCl changes from +4+4 to +2+2. D It is not an oxidation-reduction reaction because none of the oxidation numbers change.
B Fe2+(aq)→Fe3+(aq)+e−]
5Fe2+(aq)+MnO4−(aq)+8H+(aq)→5Fe3+(aq)+Mn2+(aq)+4H2O(l)5Fe2+(aq)+MnO4−(aq)+8H+(aq)→5Fe3+(aq)+Mn2+(aq)+4H2O(l) Which of the following represents the oxidation half-reaction based on the balanced ionic equation shown above? A Fe2+(aq)+e−→Fe3+(aq)\ B Fe2+(aq)→Fe3+(aq)+e− C MnO4−(aq)→Mn2+(aq)+5e− D MnO4−(aq)+5e−→Mn2+(aq)
B O2(g)O2(g)
A beaker was half filled with freshly distilled H2OH2O and placed on a hot plate. As the temperature of the water reached 100°C100°C, vigorous bubbling was observed in the beaker. The gaseous contents of the bubbles were analyzed. The presence of which of the following substances would support the claim that the observed phenomenon was a physical change? A H2(g)H2(g) B O2(g)O2(g) C CO2(g)CO2(g) D H2O(g)
C One piece of solid substance was changed into small pieces.
A chemistry teacher carried out several demonstrations, and students recorded their observations. For one of the demonstrations, a student concluded that a physical change took place, but not a chemical change. Which of the following observations could the student have made of the results of the demonstration? A Two colorless solutions were combined, and the resulting solution was pink. B When a solid was added to a liquid, sparks were produced. C One piece of solid substance was changed into small pieces. D When two solutions were combined, a precipitate formed.
(b) with 4 CO2 molecules and 2 O2 lone pairs
A mixture of CO(g) and O2(g) is placed in a container, as shown above. A reaction occurs, forming CO2(g). Which of the following best represents the contents of the box after the reaction has proceeded as completely as possible? (a) (b) with 4 CO2 molecules and 2 O2 lone pairs (c) (d)
(c) 3 Br2 + 6OH- -> H2SeO3 +Cl2 +H2O
A reaction in which the same reactant undergoes both oxidation and reduction: (c) 3 Br2 + 6OH- -> H2SeO3 +Cl2 +H2O
D not change, because the amount of AgNO3(aq)AgNO3(aq) did not change
A student combines a solution of NaCl(aq)NaCl(aq) with a solution of AgNO3(aq)AgNO3(aq), and a precipitate forms. Assume that 50.0mL50.0mL of 1.0MNaCl(aq)1.0MNaCl(aq) and 50.0mL50.0mL of 1.0MAgNO3(aq)1.0MAgNO3(aq) were combined. According to the balanced equation, if 50.0mL50.0mL of 2.0MNaCl(aq)2.0MNaCl(aq) and 50.0mL50.0mL of 1.0MAgNO3(aq)1.0MAgNO3(aq) were combined, the amount of precipitate formed would A double, because all of the coefficients are 1 B double, because the amount of one of the reactants was doubled C not change, because all of the coefficients are 1 D not change, because the amount of AgNO3(aq)AgNO3(aq) did not change
C The precipitate has a high melting point.
A student combines a solution of NaCl(aq)NaCl(aq) with a solution of AgNO3(aq)AgNO3(aq), and a precipitate forms. Which of the following is evidence that ionic bonds formed during the precipitation? A The resulting solution is colorless. B The resulting solution conducts electricity. C The precipitate has a high melting point. D The temperature of the solution did not change significantly during the precipitation.
A Ag+(aq)+Cl−(aq)→AgCl(s)
A student combines a solution of NaCl(aq)NaCl(aq) with a solution of AgNO3(aq)AgNO3(aq), and a precipitate forms. Which of the following is the balanced net ionic equation for the formation of the precipitate? A Ag+(aq)+Cl−(aq)→AgCl(s) B Na+(aq)+NO3−(aq)→NaNO3(s)Na+(aq)+NO3−(aq)→NaNO3(s) C NaCl(aq)+AgNO3(aq)→NaNO3(s)+AgCl(aq)NaCl(aq)+AgNO3(aq)→NaNO3(s)+AgCl(aq) D NaCl(aq)+AgNO3(aq)→NaNO3(aq)+AgCl(s)
D After the water has evaporated, the white crystals in the beaker have a mass of 20.0g20.0g.
A student mixes 20.0g20.0g of white KClKCl crystals with distilled water in a beaker. After the mixture was stirred, no crystals are visible and the solution is clear. After several days, all of the water evaporates and white crystals are found in the beaker. Which of following pieces of experimental evidence would best help the student to confirm that a new compound had not been made and that only a physical change occurred? A The solution does not change color after stirring. B The KClKCl crystals are no longer visible after mixing with water. C There is a temperature change in the solution during the dissolving process. D After the water has evaporated, the white crystals in the beaker have a mass of 20.0g20.0g.
A The resulting mixture was cloudy.
A student was given two clear liquids; a colorless liquid and a dark-blue liquid. The student was asked to combine the liquids in a beaker and record observations. Which of the following results, if true, would provide the best evidence that a chemical change took place when the liquids were combined? A The resulting mixture was cloudy. B The total volume of the mixture was equal to the sum of the initial volumes. C The resulting liquid was light blue. D The liquids formed two separate layers in the beaker.
A A cube of metal was changed into a flat sheet of metal.
A student was studying physical and chemical changes. The student carried out some procedures in the laboratory and recorded observations. For one of the procedures, the student concluded that a physical change took place, but not a chemical change. Which of the following could have been the results of the procedure? A A cube of metal was changed into a flat sheet of metal. B When two liquids at room temperature were combined in a beaker, the beaker became hot. C When two clear liquids were combined, the resulting mixture was cloudy. D When a colorless liquid was added to a blue liquid, the resulting solution was yellow.
B 2
Al(s)→Al3+(aq)+3e− Zn2+(aq)+2e−→Zn(s) The half-reactions for the oxidation-reduction reaction between Al(s) and Zn2+(aq) are represented above. Based on the half-reactions, what is the coefficient for Al(s) if the equation for the oxidation-reduction reaction is balanced with the smallest whole-number coefficients? A 1 B 2 C 3 D 4
C 2 NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(g)
At 27°C, five identical rigid 2.0 L vessels are filled with N2(g) and sealed. Four of the five vessels also contain a 0.050 mol sample of NaHCO3(s), NaBr(s), Cu(s), or I2(s), as shown in the diagram above. The volume taken up by the solids is negligible, and the initial pressure of N2(g) in each vessel is 720 mm Hg. All four vessels are heated to 127°C and allowed to reach a constant pressure. At 127°C, the pressure in vessel 1 is found to be higher than that in vessel 2. Which of the following reactions best accounts for the observation? A NaHCO3(s) → Na(s) + HCO3(s) B NaHCO3(s) → NaH(s) + CO3(s) C 2 NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(g) D 2 NaHCO3(s) + N2(g) → 2 NaNO3(s) + C2H2(g)
A HS−HS−
Based on the Brønsted-Lowry theory of acids and bases, which of the following species can act as both a conjugate acid and a conjugate base? A HS−HS− B CH3COO−CH3COO− C H3O+H3O+ D NH4+
(c) H atoms are both oxidized and reduced
Because pure H2 is a hazardous substance, safer and more cost effective techniques to store it as a solid for shipping purposes have been developed. One such method is the reaction represented above, which occurs at 200 degrees C. Which of the following happens to H atoms in the forward reaction? (a) H atoms are oxidized only (b) H atoms are reduced only (c) H atoms are both oxidized and reduced (d) H atoms are neither oxidized or reduced
(d) 2.00 mol
C3H8 + 5O2 -> 3CO2 + 4H2O 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.oo mol
A The initial amount of C6H12O6C6H12O6 in the container must have been 0.10mol0.10mol.
C6H12O6+6O2→6CO2+6H2O The reaction between C6H12O6 and O2O2 is represented by the balanced equation above. In an experiment, 0.30mol of CO2 was produced from the reaction of 0.05mol of C6H12O6 with excess O2. The reaction was repeated at the same temperature and in the same container, but this time 0.60mol of CO2CO2 was produced. Which of the following must be true? A The initial amount of C6H12O6C6H12O6 in the container must have been 0.10mol. B Exactly 0.30mol0.30mol of C6H12O6C6H12O6 must have reacted because CC atoms were conserved. C Exactly 0.40mol0.40mol of O2O2 of must have reacted because the temperature and container volume are the same. D More than 0.60mol0.60mol of O2O2 must have reacted because it was present in excess.
B Oxidation Half-reaction = Cu(s)→Cu2+(aq)+2e− Reduction Half-reaction = Ag+(aq)+e−→Ag(s)
Cu(s)+2AgNO3(aq)→Cu(NO3)2(aq)+2Ag(s) The reaction between solid copper and aqueous silver nitrate produces solid silver and a blue solution, as represented by the balanced equation shown above. Based on the balanced equation, which of the following identifies the oxidation and reduction half-reactions? A Oxidation Half-reaction = Cu(s)→Cu+(aq)+e− Reduction Half-reaction = Ag(s)Ag2+(aq)+2e− B Oxidation Half-reaction = Cu(s)→Cu2+(aq)+2e− Reduction Half-reaction = Ag+(aq)+e−→Ag(s) C Oxidation Half-reactionReduction Half-reactionAg+(aq)+e−→Ag(s)Ag+(aq)+e−→Ag(s)Cu(s)→Cu2+(aq)+2e−Cu(s)→Cu2+(aq)+2e− D Oxidation Half-reactionReduction Half-reactionAg2+(aq)+2e−→Ag(s)Ag2+(aq)+2e−→Ag(s)Cu(s)→Cu+(aq)+e−Cu(s)→Cu+(aq)+e−
(d) They remain dissolved in the filtrate solution
During the course of the experiment, which of the following happens to the NO3- ions? (a) They are oxidized by Cl- ions (b) They are reduced to NO2- ions (c) They are decomposed by reacting with M+ ions (d) They remain dissolved in the filtrate solution
A Pb2+(aq)+2Br−(aq)→PbBr2(s)
Equal volumes of 0.2M0.2M solutions of lead(II)(II) nitrate and potassium bromide are combined to form lead(II)(II) bromide as a yellow precipitate. Which of the following is the correct net ionic equation for the reaction? A Pb2+(aq)+2Br−(aq)→PbBr2(s) B K+(aq)+NO3−(aq)→KNO3(aq) C Pb2+(aq)+2NO3−(aq)+2K+(aq)+2Br−(aq)→2K+(aq)+2NO3−(aq)+PbBr2(s) D Pb(NO3)2(aq)+2KBr(aq)→PbBr2(s)+2KNO3(aq)
D 0.22 L of H2 has been produced
Fe(s) + 2 HCL(aq) -> FeCl2 (aq) + H2 (g) When a student adds 30.0 mL of 1.00 M HCl to 0.56 g of powdered Fe, a reaction occurs according to the equation above. When the reaction is complete at 273 K and 1.0 atm, which of the following is true? A HCl is in excess, and 0.100 mol of HCl remains unreacted. B HCl is in excess, and 0.020 mol of HCl remains unreacted. C 0.015 mol of FeCl2 has been produced. D 0.22 L of H2 has been produced
D H2O(l)H2O(l) and Cl−(aq)
For the dissolution of HCl in water represented above, which of the following pairs includes the Brønsted-Lowry bases? A HCl(aq)HCl(aq) and Cl−(aq)Cl−(aq) B HCl(aq)HCl(aq) and H3O+(aq)H3O+(aq) C H2O(l)H2O(l) and H3O+(aq)H3O+(aq) D H2O(l)H2O(l) and Cl−(aq)
B HC2O4−(aq) and C2O42-(aq)
H2C2O4(aq) + H2O(l) ⇄ H3O+(aq) + HC2O4-(aq) HC2O4-(aq) + H2O(l) ⇄ H3O+(aq) + C2O42-(aq) H2O(l) + H2O(l) ⇄ H3O+(aq) + OH- (aq) All the reactions represented above occur in an aqueous solution of oxalic acid. Which of the following represent a Brønsted-Lowry conjugate acid-base pair? A H2C2O4(aq) and C2O42-(aq) B HC2O4−(aq) and C2O42-(aq) C HC2O4-(aq) and H2O(aq) D H3O+(aq) and OH−(aq)
A It is less because more HC2H3O2(aq)HC2H3O2(aq) reacted with the base.
HC2H3O2(aq)+OH−(aq)→C2H3O2−(aq)+H2O(l)HC2H3O2(aq)+OH−(aq)→C2H3O2−(aq)+H2O(l) A student carried out a titration using HC2H3O2(aq)HC2H3O2(aq) and NaOH(aq)NaOH(aq). The net ionic equation for the neutralization reaction that occurs during the titration is represented above. The NaOH(aq)NaOH(aq) was added from a buret to the HC2H3O2(aq)HC2H3O2(aq) in a flask. The equivalence point was reached when a total of 20.0mL20.0mL of NaOH(aq)NaOH(aq) had been added to the flask. How does the amount of HC2H3O2(aq)HC2H3O2(aq) in the flask after the addition of 5.0mL5.0mL of NaOH(aq)NaOH(aq) compare to the amount of HC2H3O2(aq)HC2H3O2(aq) in the flask after the addition of 1.0mL1.0mL of NaOH(aq)NaOH(aq), and what is the reason for this result? A It is less because more HC2H3O2(aq)HC2H3O2(aq) reacted with the base. B It is the same because the half-equivalence point has not been reached. C It is the same because all of the coefficients in the neutralization equation are 1. D It is greater because HC2H3O2(aq)HC2H3O2(aq) is a proton donor.
B The temperature of the reaction mixture increases.
HCl(aq)+NaOH(aq)→NaCl(aq)+H2O(l)HCl(aq)+NaOH(aq)→NaCl(aq)+H2O(l) A student had two dilute, colorless solutions, HCl(aq)HCl(aq) and NaOH(aq)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.
C Using 200.0mLof 0.100MK2SO3(aq)and 200.0mL of 0.200MHNO3(aq), because these are the required stoichiometric amounts
K2SO3(aq)+2HNO3(aq)→2KNO3(aq)+SO2(g)+H2O(l)K2SO3(aq)+2HNO3(aq)→2KNO3(aq)+SO2(g)+H2O(l) According to the balanced chemical equation above, when 100.0mL100.0mL of 0.100MK2SO3(aq)0.100MK2SO3(aq) is mixed with 100.0mL100.0mL of 0.200MHNO3(aq)0.200MHNO3(aq) at 30°C30°C and 1 atm1 atm, the volume of SO2SO2 gas produced is 0.24 L0.24 L. If it is assumed that the reaction goes to completion, which of the the following changes would double the volume of SO2SO2 produced at the same temperature and pressure? (For each change, assume that the other solutions and volumes remain the same.) A Using 200.0mL200.0mL of the 0.100MK2SO3(aq)0.100MK2SO3(aq), because it then becomes the reactant in excess B Using 200.0mL200.0mL of the 0.200MHNO3(aq)0.200MHNO3(aq), because the volume of SO2SO2 produced is inversely proportional to the number of moles at constant temperature and pressure C Using 200.0mL200.0mL of 0.100MK2SO3(aq)0.100MK2SO3(aq) and 200.0mL200.0mL of 0.200MHNO3(aq)0.200MHNO3(aq), because these are the required stoichiometric amounts D Using 400.0mL400.0mL of 0.100MK2SO3(aq)0.100MK2SO3(aq) and 200.0mL200.0mL of 0.200MHNO3(aq)0.200MHNO3(aq), because this provides the same number of moles of each reactant
A Bubbles formed when the two solutions were combined.
Na2CO3(aq)+2HCl(aq)→2NaCl(aq)+H2O(l)+CO2(g)Na2CO3(aq)+2HCl(aq)→2NaCl(aq)+H2O(l)+CO2(g) A student combined two colorless aqueous solutions. One of the solutions contained Na2CO3Na2CO3 as the solute and the other contained HClHCl. The chemical reaction that took place is represented by the equation above. What experimental result would be evidence that a chemical reaction took place when the solutions were combined? A Bubbles formed when the two solutions were combined. B The total volume of the mixture is close to the sum of the initial volumes. C The resulting solution is colorless. D The resulting solution conducts electricity.
(d) where AgCl sticks together and Na and NO3 are floating
The diagrams above represent solutes present in two different dilute aqueous solutions before they were mixed. Water molecules are not shown. When the solutions were combined, a precipitation reaction took place. Which of the diagrams below is the best particle representation of the mixture after the precipitation reaction occurred? (a) (b) (c) (d) where AgCl sticks together and Na and NO3 are floating
B Sr2+(aq)+SO42−(aq)→SrSO4(s)
The reaction between aqueous strontium chloride (SrCl2)(SrCl2) and aqueous potassium sulfate (K2SO4)(K2SO4) forms a precipitate of strontium sulfate (SrSO4)(SrSO4). Which of the following represents the net ionic equation for the reaction? A Cl−(aq)+K+(aq)→KCl(aq) B Sr2+(aq)+SO42−(aq)→SrSO4(s) C Sr2+(aq)+2Cl−(aq)+SO42−(aq)+2K+(aq)→SrSO4(s)+2Cl−(aq)+2K+(aq) D SrCl2(aq)+K2SO4(aq)→SrSO4(s)+2KCl(aq)
D Rinse the buret two times: each time with some of the titrant solution.
When a buret is rinsed before a titration, which of the techniques below is the best procedure? A Rinse the buret one time with some of the titrant solution. B Rinse the buret one time with some of the titrant solution and then dry the buret in an oven. C Rinse the buret two times: once with some of the titrant solution, then once with distilled water. D Rinse the buret two times: each time with some of the titrant solution. E Rinse the buret two times: each time with distilled water.
B It is an acid-base reaction in which a proton is exchanged from H2OH2O to NH3NH3.
Which of the following best describes the process represented above that takes place when NH3NH3 is added to water? A It is a single replacement reaction in which an electron pair on NN is replaced with an HH atom. B It is an acid-base reaction in which a proton is exchanged from H2OH2O to NH3NH3. C It is a precipitation reaction in which NH4OHNH4OH, an insoluble solid, is produced. D It is an oxidation-reduction reaction in which the oxidation number of NN changes from −3−3 to −4−4.
D HF(aq)+OH−(aq)→H2O(l)+F−(aq)
Which of the following is the correct net ionic equation of the neutralization reaction between hydrofluoric acid and sodium hydroxide in aqueous solution? A HF(aq)+NaOH(aq)→H2O(l)+NaF(aq)HF(aq)+NaOH(aq)→H2O(l)+NaF(aq) B HF(aq)+NaOH(aq)→NaH(aq)+FOH(aq)HF(aq)+NaOH(aq)→NaH(aq)+FOH(aq) C H+(aq)+OH−(aq)→H2O(l)H+(aq)+OH−(aq)→H2O(l) D HF(aq)+OH−(aq)→H2O(l)+F−(aq)
B NH3(aq)+H+(aq)→NH4+(aq)
Which of the following is the correct net ionic equation of the reaction that occurs when aqueous solutions of ammonia and hydrochloric acid are combined? A NH3(aq)+HCl(aq)→NH4Cl(aq)NH3(aq)+HCl(aq)→NH4Cl(aq) B NH3(aq)+H+(aq)→NH4+(aq) C NH3(aq)+HCl(aq)→NH4+(aq)+Cl−(aq)NH3(aq)+HCl(aq)→NH4+(aq)+Cl−(aq) D NH3(aq)+H+(aq)+Cl−(aq)→NH4+(aq)+Cl−(aq)NH3(aq)+H+(aq)+Cl−(aq)→NH4+(aq)+Cl−(aq)
(c) h2 and 02 separate pairs floating
Which of the following particulate diagrams best shows the formation of water vapor from hydrogen gas and oxygen gas in the rigid container at 125 degrees C? (a) (b) (c) h2 and 02 separate pairs floating (d)
(d) NO3-- -> NO
Which of the following represents a process in which a species is reduced? (a) Ca -> Ca2+ (b) Hg -> Hg22+ (c) Fe2+ -> Fe3+ (d) NO3-- -> NO (e) SO32- 0> SO42-
D NO3-(aq) → NO(g)
Which of the following represents a process in which a species is reduced? A Ca(s) → Ca2+(aq) B Hg(l) → Hg22+(aq) C Fe2+(aq) → Fe3+(aq) D NO3-(aq) → NO(g) E SO32-(aq) → SO42-(aq)
D It is an oxidation-reduction reaction because zinc is oxidized and hydrogen is reduced.
Zn(s)+2HCl(aq)→ZnCl2(aq)+H2(g)Zn(s)+2HCl(aq)→ZnCl2(aq)+H2(g) When the reaction represented above proceeds, heat is produced. Which of the following best describes the reaction? A It is a combustion reaction because heat is produced by the reaction. B It is a double replacement reaction because 2Cl2Cl atoms are added to ZnZn. C It is an acid-base reaction because HClHCl is an acid that is capable of exchanging H+H+. D It is an oxidation-reduction reaction because zinc is oxidized and hydrogen is reduced.
