Chemical concepts are applied in candy making. A recipe for making lollipops is shown below. Hard-Candy Lollipops Recipe

Transcription

1 Name: Short Answer Review Honors Chemistry Base your answers to questions 1 and 2 on the information below and on your knowledge of chemistry. Chemical concepts are applied in candy making. A recipe for making lollipops is shown below. Ingredients: 414 grams of sugar 177 grams of water 158 milliliters of light corn syrup Hard-Candy Lollipops Recipe Step 1: In a saucepan, mix the sugar and water. Heat this mixture, while stirring, until all of the sugar dissolves. Step 2: Add the corn syrup and heat the mixture until it boils. Step 3: Continue boiling the mixture until the temperature reaches 143 C at standards pressure. Step 4: Remove the pan from the heat and allow it to stand until the bubbling stops. Pour the mixture into lollipop molds that have been coated with cooking oil spray. 1. Explain, in terms of the concentration of sugar molecules, why the boiling point of the mixture in step 3 increases as water evaporates from the mixture. 2. Determine the concentration, expressed as percent by mass, of the sugar dissolved in the mixture produced in step 1.

2 Base your answers to questions 3 and 4 on the information below. In the gold foil experiment, a thin sheet of gold was bombarded with alpha particles. Almost all the alpha particles passed straight through the foil. Only a few alpha particles were deflected from their original paths. 3. Explain, in terms of charged particles, why some of the alpha particles were deflected. 4. State one conclusion about atomic structure based on the observation that almost all alpha particles passed straight through the foil. 5. in the space below, write an electron configuration for a silicon atom in an excited state. Base your answers to questions 6 and 7 on the information below. Two isotopes of potassium are K-37 and K Explain, in terms of subatomic particles, why K-37 and K-42 are isotopes of potassium.

3 7. How many valence electrons are in an atom of K-42 in the ground state? Base your answers to questions 8 through 10 on the information below and on your knowledge of chemistry. The diagram below represents three elements in Group 13 and three elements in Period 3 and their relative positions on the Periodic Table. Some elements in the solid phase exist in different forms that vary in their physical properties. For example, at room temperature, red phosphorus has a density of 2.16 g/cm 3 and white phosphorus has a density of g/cm Identify one element from the diagram that will combine with phosphorus in the same ratio of atoms as the ratio in aluminum phosphide. 9. Compare the number of atoms per cubic centimeter in red phosphorus with the number of atoms per cubic centimeter in white phosphorus.

4 10. Consider the Period 3 elements in the diagram in order of increasing atomic number. State the trend in electronegativity for these elements. Base your answers to questions 11 through 13 on the information below and on your knowledge of chemistry. A student made a copper bracelet by hammering a small copper bar into the desired shape. The bracelet has a mass of 30.1 grams and was at a temperature of 21 C in the classroom. After the student wore the bracelet, the bracelet reached a temperature of 33 C. Later, the student removed the bracelet and placed it on a desk at home, where it cooled from 33 C to 19 C. The specific heat capacity of copper is J/g K. 11. Explain, in terms of chemical activity, why copper is a better choice than iron to make the bracelet. 12. Show a numerical setup for calculating the amount of heat released by the bracelet as it cooled on the desk. 13. Determine the number of moles of copper in the bracelet.

5 Base your answers to questions 14 and 15 on the information below. In a titration, a few drops of an indicator are added to a flask containing 35.0 milliliters of HNO3(aq) of unknown concentration. After 30.0 milliliters of 0.15 M NaOH(aq) solution is slowly added to the flask, the indicator changes color, showing the acid is neutralized. 14. Complete the equation below for this neutralization reaction by writing the formula of each product. HNO3(aq) + NaOH(aq) The volume of the NaOH(aq) solution is expressed to what number of significant figures? Base your answers to questions 16 through 18 on the information below. A tablet of one antacid contains citric acid, H3C6H5O7, and sodium hydrogen carbonate, NaHCO3. When the tablet dissolves in water, bubbles of CO2 are produced. This reaction is represented by the incomplete equation below. H3C6H5O7(aq) + 3NaHCO3(aq) Na3C6H5O7(aq) + 3CO2(g) + 3 ( ) 16. Determine the total number of moles of sodium hydrogen carbonate that will completely react with mole of citric acid. 17. State evidence that a chemical reaction occurred when the tablet was placed in the water.

6 18. write the formula of the missing product. Base your answers to questions 19 through 21 on the information below and on your knowledge of chemistry. Rubbing alcohol is a product available at most pharmacies and supermarkets. One rubbing alcohol solution contains 2-propanol and water. The boiling point of 2-propanol is 82.3 C at standard pressure. 19. Determine the vapor pressure of water at a temperature equal to the boiling point of the 2-propanol. 20. Identify a strong intermolecular force of attraction between an alcohol molecule and a water molecule in the solution. 21. Draw a structural formula formula for the 2-propanol.

7 22. What is the mass of KNO3(s) that must dissolve in 100. grams of water to form a saturated solution at 50. C? Base your answers to questions 23 and 24 on Heat is added to a sample of liquid water, starting at 80.ºC, until the entire sample is a gas at 120.ºC. This process, occurring at standard pressure, is represented by the balanced equation below. H2O( ) + heat H2O(g) 23. On the diagram below, complete the heating curve for this physical change. 24. In the box below, using the key, draw a particle diagram to represent at least five molecules of the product of this physical change at 120. C.

8 Base your answers to questions 25 through 27 on the information below. A soft-drink bottling plant makes a colorless, slightly acidic carbonated beverage called soda water. During production of the beverage, CO2(g) is dissolved in water at a pressure greater than 1 atmosphere. The bottle containing the solution is capped to maintain that pressure above the solution. As soon as the bottle is opened, fizzing occurs due to CO2(g) being released from the solution. 25. State the relationship between, the solubility of CO2(g) in water and the temperature of the aqueous solution. 26. Write the chemical name of the acid in soda water. 27. Explain why CO2(g) is released when a bottle of soda water is opened. 28. Base your answer to the following question on the information below and on your knowledge of chemistry. A few pieces of dry ice,, at are placed in a flask that contains air at. The flask is sealed by placing an uninflated balloon over the mouth of the flask. As the balloon inflates, the dry ice disappears and no liquid is observed in the flask. Compare the entropy of the CO2 molecules in the dry ice to the entropy of the CO2 molecules in the inflated balloon.

9 Base your answers to questions 29 and 30 on the information below and on your knowledge of chemistry. Ethene and hydrogen can react at a faster rate in the presence of the catalyst platinum. The equation below represents a reaction between ethene and hydrogen. 29. Explain why the reaction is classified as an addition reaction. 30. Explain, in terms of activation energy, why the catalyzed reaction occurs at a faster rate.

10 Base your answers to questions 31 and 32 on the information below. At 550 C, 1.00 mole of CO2(g) and 1.00 mole of H2(g) are placed in a 1.00-liter reaction vessel. The substances react to form CO(g) and H2O(g). Changes in the concentrations of the reactants and the concentrations of the products are shown in the graph below. 31. What can be concluded from the graph about the concentrations of the reactants and the concentrations of the products between time t 1 and time t 2? 32. Determine the change in the concentration of CO2(g) between time t 0 and time t 1.

11 Base your answers to questions 33 and 34 on the information below. Many esters have distinctive odors, which lead to their widespread use as artificial flavorings and fragrances. For example, methyl butanoate has an odor like pineapple and ethyl methanoate has an odor like raspberry. 33. What is a chemical name for the alcohol that reacts with methanoic acid to produce the ester that has an odor like raspberry? 34. Draw a structural formula for the ester that has an odor like pineapple. Base your answers to questions 35 and 36 on the equation below, which represents an organic compound reacting with bromine. 35. What is the gram-formula mass of the product in this reaction? 36. What is the IUPAC name for the organic compound that reacts with Br2?

12 37. State one difference between voltaic cells and electrolytic cells. Include information about both types of cells in your answer. Base your answers to questions 38 through 40 on the diagram of a voltaic cell provided below. 38. Explain the function of the salt bridge. 39. Write an equation for the half-reaction that occurs at the zinc electrode. 40. Indicate with one or more arrows the direction of electron flow through the wire.

13 Base your answers to questions 41 through 44 on the following redox reaction, which occurs spontaneously. 41. State what happens to the number of protons in a Zn atom when it changes to Zn 2+ as the redox reaction occurs. 42. Balance the equation using the smallest whole-number coefficients. 43. Which species loses electrons and which species gains electrons? 44. Which half-reaction occurs at the cathode?

14 Base your answers to questions 45 through 47 on the information below. Some carbonated beverages are made by forcing carbon dioxide gas into a beverage solution. When a bottle of one kind of carbonated beverage is first opened, the beverage has a ph value of After the beverage bottle is left open for several hours, the hydronium ion concentration in the beverage solution decreases to of the original concentration. Determine the new ph of the beverage solution. 46. Using Table M, identify one indicator that is yellow in a solution that has the same ph value as this beverage. 47. State, in terms of the ph scale, why this beverage is classified as acidic. 48. Base your answer to the following question on the information below and on your knowledge of chemistry. A breeder reactor is one type of nuclear reactor. In a breeder reactor, uranium-238 is transformed in a series of nuclear reactions into plutonium-239. The plutonium-239 can undergo fission as shown in the equation below. The X represents a missing product in the equation. Write a notation for the nuclide represented by missing product X in this equation.

15 Base your answers to questions 49 and 50 on the information below and on your knowledge of chemistry. lodine has many isotopes, but only iodine-127 is stable and is found in nature. One radioactive iodine isotope, I-108, decays by alpha particle emission. Iodine-131 is also radioactive and has many important medical uses. 49. Determine the total time required for an 80.0-gram sample of I-131 to decay until only 1.25 grams of the sample remains unchanged. 50. Explain, in terms of protons and neutrons, why I-127 and I-131 are different isotopes of iodine. Base your answers to questions 51 and 52 on the information below and on your knowledge of chemistry. During a laboratory activity, a student places 25.0 ml of HCl(aq) of unknown concentration into a flask. The student adds four drops of phenolphthalein to the solution in the flask. The solution is titrated with M KOH(aq) until the solution appears faint pink. The volume of KOH(aq) added is 18.5 ml. 51. Determine the concentration of the HCl(aq) solution, using the titration data. 52. Describe one laboratory safety procedure that should be used if a drop of the KOH(aq) is spilled on the arm of the student.

16 Base your answers to questions 53 through 55 on the information below. A hydrate is a compound that has water molecules within its crystal structure. The formula for the hydrate CuSO4 5H2O(s) shows that there are five moles of water for every one mole of CuSO4(s). When CuSO4 5H2O(s) is heated, the water within the crystals is released, as represented by the balanced equation below. CuSO4 5H2O(s) > CuSO4(s) + 5H2O(g) A student first masses an empty crucible (a heat-resistant container). The student then masses the crucible containing a sample of CuSO4 5H2O(s). The student repeatedly heats and masses the crucible and its contents until the mass is constant. The student s recorded experimental data and calculations are shown below. 53. Explain why the sample in the crucible must be heated until the constant mass is reached. 54. Use the student s data to show a correct numerical setup for calculating the percent composition by mass of water in the hydrate.

17 55. Identify the total number of significant figures recorded in the calculated mass of CuSO 4 5H2O(s).

18 Answer Key SA Review 1. The boiling point of the mixture increases as water evaporates because the concentration of dissolved molecules increases. An increase in the concentration of sugar particles increases the boiling point % 3. Alpha particles are positive and are repelled by the nucleus that is also positive. Both protons and alpha particles are positively charged so they repel each other. Protons and alpha particles have the same charge. 4. Atoms are mostly empty space Acceptable responses include, but are not limited to: same number of protons, different number of neutrons K-37 has fewer neutrons than K-42. same element; different number of neutrons 7. 1 or one. 8. Ga, indium, element 31, element White phosphorous has fewer atoms per cm 3. Red has more. 10. As atomic number increases, the electronegativity increases. Electronegativity increases. from lower to higher 11. Copper is less chemically active than iron, so copper is less likely to react with substances in the air or on the skin. Iron is more active. Fe oxidizes more easily. 12. q = (30.1 g)(0.385 J/g K)(19ºC 33ºC) (30.1 g)(306 K 292 K)(0.385 J/g K) (0.385)(30.1)(14) mol or for any value from 0.47 mol to mol, inclusive, or for 0.5 mol 14. NaNO3(aq) + H2O( ) or HOH + NaNO or three mol. Significant figures do not need to be shown. 17. Acceptable responses include, but are not limited to: The reactants and products are different chemicals. Bonds were broken and bonds were formed. A gas was created. 18. H2O kpa 52 kpa 20. hydrogen bonding dipole-dipole g 2g 23. a line is drawn horizontally to represent the phase change and extending the line with a positive slope to represent the gas phase, only. 24. Five water molecules are drawn and all of the particles drawn represent the gas phase. 25. The solubility of CO2 (g) decreases as the temperature of the solution increases; As temperature decreases, solubility of CO2 increases. 26. Carbonic Acid 27. The pressure above the solution decreases, so the CO2 (g) is less soluble in the solution; The pressure is less, so the CO2 has lower solubility. 28. The CO2 molecules in the dry ice have less entropy than the CO2 molecules in the inflated balloon. The CO2 gas in the balloon is more disordered. less for CO2(s) 29. Hydrogen atoms are added to the ethene molecule at the site of the carbon-carbon double bond to form a single molecule. Two reactants combine to form a single product. Two subtances form one. Two hydrogen atoms are added at C C An unsaturated reactant becomes a saturated product. The reaction is a hydrogenated reaction, which is a type of addition reaction. 30. The catalyzed reaction pathway has a lower activation energy than the original reaction. Less energy is needed. 31. Between time t 1 and time t 2, the concentrations of the reactants and the concentrations of the products are no longer changing. The concentrations of the reactants and the products remain constant. The concentration of each reactant is 0.73 mol/l, and the concentration of each product is 0.27 mol/l mol/l 0.27 mol/l 33. Examples: ethanol ethyl alcohol

19 Answer Key SA Review Examples: 202 g/mol g/mol 36. propene 37. Examples: Voltaic cells produce energy; electrolytic cells consume energy. voltaic changes chemical energy to electrical, electrolytic does the opposite Voltaic cells involve spontaneous redox reactions; electrolytic cells involve non-spontaneous redox reactions. 38. Examples: migration of ions maintains neutrality prevents polarization 39. Zn 0 Zn e or Zn 0 2e Zn The number of protons remains the same or is unaffected Zn (not Zn 2+ ) loses electrons and Cr 3+ (not Cr) gains electrons e + 2 Cr 3+ 2 Cr or reduction or chromium half-reaction or Cr e Cr bromthymol blue bromcresol green thymol blue 47. The beverage is acidic because its ph value is below 7. A ph of 3 is in the acid range on the ph scale Ce 144 Ce cerium-144 Ce d 48.0 d 48.1 d 50. I-127 atoms and I-131 atoms have the same number of protons, but different numbers of neutrons. Both have 53 p, but I-127 has 74 n while I-131 has 78 n. They have the same atomic number but different mass numbers. same atomic number but different numbers of neutrons The only difference is the number of neutrons M 0.11 M 0.1 M 52. The student should immediately place his/her arm under running water to dilute and wash away the KOH(aq). Tell the teacher 53. Examples: Until the samples reaches a constant mass, the student cannot be sure that all the water has been removed. to make sure all the water is heated out of the sample