AP Chem unit 4 hw

C6H12O6+6O2→6CO2+6H2OC6H12O6+6O2→6CO2+6H2O The reaction between C6H12O6C6H12O6and O2O2is represented by the balanced equation above. In an experiment, 0.30mol0.30molof CO2CO2was produced from the reaction of 0.05mol0.05molof C6H12O6C6H12O6with excess O2O2. The reaction was repeated at the same temperature and in the same container, but this time 0.60mol0.60molof CO2CO2was produced. Which of the following must be true? A The initial amount of C6H12O6C6H12O6 in the container must have been 0.10mol0.10mol. B Exactly 0.30mol0.30molof C6H12O6C6H12O6must have reacted because CCatoms were conserved. C Exactly 0.40mol0.40molof O2O2of 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.

A

2F2(g)+2NaOH(aq)→OF2(g)+2NaF(aq)+H2O(l)2F2(g)+2NaOH(aq)→OF2(g)+2NaF(aq)+H2O(l) A 2mol2mol sample of F2(g)F2(g) reacts with excess NaOH(aq)NaOH(aq) according to the equation above. If the reaction is repeated with excess NaOH(aq)NaOH(aq) but with 1 mol1 mol of F2(g)F2(g), which of the following is correct? A: The amount of OF2(g) produced is doubled. B: The amount of OF2(g)OF2(g) produced is halved. C: The amount of NaF(aq)NaF(aq) produced remains the same. D: The amount of NaF(aq)NaF(aq) produced is doubled.

B

A student places a sample of a pure metal in a crucible and heats it strongly in air. Data from the experiment are given in the table above. The final mass was determined after the sample was cooled to room temperature. Which of the following statements related to the experiment is correct? A The mass of the sample decreased, so physical changes occurred as the metal first melted and then boiled out of the crucible. B The mass of the sample increased, so a chemical change occurred when bonds formed between the metal and another substance. C There was nothing for the metal to react with, so only a physical change could have occurred. D The sample was only heated, so neither a physical nor a chemical change occurred.

B

Al(s)→Al3+(aq)+3e−Al(s)→Al3+(aq)+3e− Zn2+(aq)+2e−→Zn(s)Zn2+(aq)+2e−→Zn(s) The half-reactions for the oxidation-reduction reaction between Al(s)Al(s) and Zn2+(aq)Zn2+(aq) are represented above. Based on the half-reactions, what is the coefficient for Al(s)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

B

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.

B

A student was asked to formulate a hypothesis about what would happen if 100.mL100.mLof 0.1MNaOH(aq)0.1MNaOH(aq)at 25°C25°Cwas combined with 100.mL100.mLof 0.1MMgCl2(aq)0.1MMgCl2(aq)at 25°C25°C. Which of the following hypotheses indicates that the student thought a chemical change would occur? A The volume of the resulting solution will be equal to the sum of the volumes of the original solutions. B The mass of the resulting solution will be equal to the sum of the masses of the original solutions. C The resulting solution would contain a precipitate. D The resulting solution will be clear.

C

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.

D

HCl(aq)+H2O(l)→H3O+(aq)+Cl−(aq)HCl(aq)+H2O(l)→H3O+(aq)+Cl−(aq) For the dissolution of HClHClin 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)

D

MgCl2(aq)+2NaOH(aq)→2NaCl(aq)+Mg(OH)2(s)MgCl2(aq)+2NaOH(aq)→2NaCl(aq)+Mg(OH)2(s) A 100mL100mLsample of 0.1MMgCl2(aq)0.1MMgCl2(aq)and a 100mL100mLsample of 0.2MNaOH(aq)0.2MNaOH(aq)were combined, and Mg(OH)2(s)Mg(OH)2(s)precipitated, as shown by the equation above. If the experiment is repeated using solutions of the same molarity, which of the following changes in volume will double the amount of Mg(OH)2(s)Mg(OH)2(s)produced? A Using the same volume of MgCl2(aq)MgCl2(aq)but twice the volume of NaOH(aq)NaOH(aq) B Using twice the volume of MgCl2(aq)MgCl2(aq)but half the volume of NaOH(aq)NaOH(aq) C Using twice the volume of MgCl2(aq)MgCl2(aq)but the same volume of NaOH(aq)NaOH(aq) D Using twice the volume of MgCl2(aq)MgCl2(aq)and twice the volume of NaOH(aq)

D

Ni(s)→Ni2+(aq)+2e−Ni(s)→Ni2+(aq)+2e− Ag+(aq)+e−→Ag(s)Ag+(aq)+e−→Ag(s) Which of the following is the balanced net ionic equation for an oxidation-reduction reaction between Ag+(aq)Ag+(aq) and Ni(s)Ni(s) based on the half-reactions represented above? A: Ag+(aq)+Ni(s)→Ag(s)+Ni2+(aq)Ag+(aq)+Ni(s)→Ag(s)+Ni2+(aq) B: 2Ag+(aq)+Ni(s)→Ag(s)+2Ni2+(aq)2Ag+(aq)+Ni(s)→Ag(s)+2Ni2+(aq) C: Ag+(aq)+2Ni(s)→Ag(s)+2Ni2+(aq)Ag+(aq)+2Ni(s)→Ag(s)+2Ni2+(aq) D: 2Ag+(aq)+Ni(s)→2Ag(s)+Ni2+(aq)

D

Which of the following is the net ionic equation for the reaction between aqueous sodium fluoride and hydrochloric acid? A NaF(aq)+HCl(aq)→NaCl(aq)+HF(aq)NaF(aq)+HCl(aq)→NaCl(aq)+HF(aq) B Na+(aq)+F−(aq)+H+(aq)+Cl−(aq)→Na+(aq)+Cl−(aq)+HF(aq)Na+(aq)+F−(aq)+H+(aq)+Cl−(aq)→Na+(aq)+Cl−(aq)+HF(aq) C Na+(aq)+Cl−(aq)→NaCl(aq)Na+(aq)+Cl−(aq)→NaCl(aq) D F−(aq)+H+(aq)→HF(aq)

D