UNIDAD EDUCATIVA MONTE TABOR-NAZARET QUÍMICA SEGUNDO DE BACHILLERATO Actividades Refuerzo Académicas y/o Preparación Examen Remedial

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1 UNIDAD EDUCATIVA MONTE TABOR-NAZARET QUÍMICA SEGUNDO DE BACHILLERATO Actividades Refuerzo Académicas y/o Preparación Examen Remedial ALUMNO: AÑO DE BACHILLERATO: 2 do PARALELO: FECHA: PROFESOR: Yesenia Uzca/Ángel Cherrez Para apoyar al desarrollo de destrezas y contenidos de la asignatura en base a los temarios de supletorios publicados en la página web se recomienda trabajar las siguientes actividades académicas a realizarse en casa previo a las fechas de exámenes remediales. Adicionalmente para el estudio y preparación es necesario utilizar las diferentes herramientas trabajadas durante el año lectivo como actividades en clase, tareas, lecciones, evaluaciones sumativas, exámenes quimestrales y actividades de preparación exámenes supletorios. Semana 1: DESARROLLE LAS SIGUIENTES ACTIVIDADES g of NaNO 3 (M r = 85) is dissolved in water to prepare 0.20 dm 3 of solution. What is the concentration of the resulting solution in mol dm 3? A B. 0.1 C. 0.2 D How many molecules are present in a drop of ethanol, C 2 H 5 OH, of mass g? (L = mol 1 ) A B C D

2 3. What mass, in g, of hydrogen is formed when 3 mol of aluminium react with excess hydrochloric acid according to the following equation? A. 3.0 B. 4.5 C. 6.0 D Al(s) + 6HCl(aq) 2AlCl 3 (aq) + 3H 2 (g) 4. What is the total number of hydrogen atoms in 1.0 mol of benzamide, C 6 H 5 CONH 2? A. 7 B C D Chloroethene, C 2 H 3 Cl, reacts with oxygen according to the equation below. 2C 2 H 3 Cl(g) + 5O 2 (g) 4CO 2 (g) + 2H 2 O(g) + 2HCl(g) What is the amount, in mol, of H 2 O produced when 10.0 mol of C 2 H 3 Cl and 10.0 mol of O 2 are mixed together, and the above reaction goes to completion? A B C D A fixed mass of gas has a certain volume at a temperature of 50 C. What temperature is required to double its volume while keeping the pressure constant? A. 100 K B. 323 K C. 373 K D. 646 K

3 7. What is the concentration of NaCl, in mol dm 3, when 10.0 cm 3 of mol dm 3 NaCl solution is added to 30.0 cm 3 of mol dm 3 NaCl solution? A B C D Which of the following is consistent with Avogadro s law? P A. = constant (V, n constant) T V B. = constant (P, n constant) T C. Vn = constant (P, T constant) V D. = constant (P, T constant) n mol of aluminium reacts with oxygen to form aluminium oxide. What is the amount of oxygen, in mol, needed for complete reaction? A. 1.5 B. 3.0 C. 4.5 D Al(s) + 3O 2 (g) 2Al 2 O 3 (s) 10. Equal masses of the metals Na, Mg, Ca and Ag are added to separate samples of excess HCl(aq). Which metal produces the greatest total volume of H 2 (g)? A. Na B. Mg C. Ca D. Ag

4 cm 3 of water is added to a solution of 200 cm 3 of 0.5 mol dm 3 sodium chloride. What is the concentration of sodium chloride in the new solution? A mol dm 3 B. 0.1 mol dm 3 C. 0.2 mol dm 3 D. 0.3 mol dm dm 3 of carbon monoxide, CO(g), and 2 dm 3 of oxygen, O 2 (g), at the same temperature and pressure are mixed together. Assuming complete reaction according to the equation given, what is the maximum volume of carbon dioxide, CO 2 (g), in dm 3, that can be formed? 2CO(g) + O 2 (g) 2CO 2 A. 3 B. 4 C. 5 D What volume of sulfur trioxide, in cm 3, can be prepared using 40 cm 3 sulfur dioxide and 20 cm 3 oxygen gas by the following reaction? Assume all volumes are measured at the same temperature and pressure. A. 20 B. 40 C. 60 D. 80 2SO 2 (g) + O 2 (g) 2SO 3 (g) 14. The percentage by mass of calcium carbonate in eggshell was determined by adding excess hydrochloric acid to ensure that all the calcium carbonate had reacted. The excess acid left was then titrated with aqueous sodium hydroxide. (a) A student added cm 3 of mol dm 3 HCl to g of eggshell. Calculate the amount, in mol, of HCl added.

5 (b) The excess acid requires cm 3 of mol dm 3 NaOH for neutralization. Calculate the amount, in mol, of acid that is in excess. (c) Determine the amount, in mol, of HCl that reacted with the calcium carbonate in the eggshell. (d) State the equation for the reaction of HCl with the calcium carbonate in the eggshell. (e) Determine the amount, in mol, of calcium carbonate in the sample of the eggshell. (f) Calculate the mass and the percentage by mass of calcium carbonate in the eggshell sample.

6 (3) (g) Deduce one assumption made in arriving at the percentage of calcium carbonate in the eggshell sample. (Total 11 marks) 15. Biodiesel makes use of plants ability to fix atmospheric carbon by photosynthesis. Many companies and individuals are now using biodiesel as a fuel in order to reduce their carbon footprint. Biodiesel can be synthesized from vegetable oil according to the following reaction. (b) For part of her extended essay investigation into the efficiency of the process, a student reacted a pure sample of a vegetable oil (where R = C 17 H 33 ) with methanol. The raw data recorded for the reaction is below. Mass of oil = g Mass of methanol = g Mass of sodium hydroxide = 3.5 g Mass of biodiesel produced = g The relative molecular mass of the oil used by the student is Calculate the amount (in moles) of the oil and the methanol used, and hence the amount (in moles) of excess methanol.

7 (3) (c) The reversible arrows in the equation indicate that the production of biodiesel is an equilibrium process. (iii) Suggest a reason why excess methanol is used in this process (iv) State and explain the effect that the addition of the sodium hydroxide catalyst will have on the position of equilibrium (d) The reactants had to be stirred vigorously because they formed two distinct layers in the reaction vessel. Explain why they form two distinct layers and why stirring increases the rate of reaction. (e) Calculate the percentage yield of biodiesel obtained in this process.

8 (f) When biodiesel is combusted it produces carbon dioxide. Explain why the use of biodiesel as a fuel does not significantly contribute to global warming. (Total 14 marks) 16. Smog is common in cities throughout the world. One component of smog is PAN (peroxyacylnitrate) which consists of 20.2 % C, 11.4 % N, 65.9 % O and 2.50 % H by mass. Determine the empirical formula of PAN, showing your working (Total 3 marks) Semana 2: mol of aluminium hydroxide is mixed with mol of sulfuric acid, and the following reaction occurs: 2Al(OH) 3 (s) + 3H 2 SO 4 (aq) Al 2 (SO 4 ) 3 (aq) + 6H 2 O(l) (a) Determine the limiting reactant.

9 (b) Calculate the mass of Al 2 (SO 4 ) 3 produced. (c) Determine the amount (in mol) of excess reactant that remains. (d) Define a Brønsted-Lowry acid Brønsted-Lowry acid (e) H 2 SO 4 (aq) is a strong acid. State the name and the formula of any weak acid. (Total 7 marks) 2. Consider the overall reaction taking place in a voltaic cell. Ag 2 O(s) + Zn(s) + H 2 O(l) 2Ag(s) + Zn(OH) 2 (s) What is the role of zinc in the cell? A. The positive electrode and the oxidizing agent. B. The positive electrode and the reducing agent. C. The negative electrode and the oxidizing agent. D. The negative electrode and the reducing agent. (Total 1 mark)

10 3. A voltaic cell is constructed from two half-cells as illustrated below. (i) Use Table 14 of the Data Booklet to deduce the equation for the spontaneous reaction occurring in this cell. (ii) Calculate the standard potential for this cell. (iii) State the conditions necessary for the potential of the cell to equal that calculated in part (ii) using the data from Table 14. (Total 3 marks) 4. Using the data below and data from Table 14 of the Data Booklet, predict and explain which metal, cadmium or chromium, may be obtained by electrolysis of separate aqueous solutions of Cd 2+ (aq) ions and Cr 2+ (aq) ions. E O / V Cd 2+ (aq) + 2e Cd(s) 0.40 Cr 2+ (aq) + 2e Cr(s) 0.91

11 (Total 2 marks) 5. Nitrogen monoxide may be removed from industrial emissions via a reaction with ammonia as shown by the equation below. 4NH 3 (g) + 6NO(g) 5N 2 (g) + 6H 2 O(l) (i) Deduce the oxidation number of the nitrogen in the reactants and product. (3) (ii) Deduce the oxidation and reduction half-equations and identify the oxidizing agent for the reaction. (3) (iii) 30.0 dm 3 of ammonia reacts with 30.0 dm 3 of nitrogen monoxide at 100 C. Identify which gas is in excess and by how much and calculate the volume of nitrogen produced. (Total 8 marks)

12 6. Iron is more reactive than copper. (i) Draw a labelled diagram of a voltaic cell made from an Fe(s) / Fe 2+ (aq) half-cell connected to a Cu(s) / Cu 2+ (aq) half-cell. In your diagram identify the positive electrode (cathode), the negative electrode (anode) and the direction of electron flow in the external circuit. (4) (ii) Deduce the half-equations for the reactions taking place at the positive electrode (cathode) and negative electrode (anode) of this voltaic cell. (iii) Deduce the overall equation for the reaction taking place in the voltaic cell and determine which species acts as the oxidizing agent and which species has been reduced. (Total 8 marks) 7. Consider the following three redox reactions. Cd(s) + Ni 2+ (aq) Cd 2+ (aq) + Ni(s) Ni(s) + 2Ag + (aq) Ni 2+ (aq) + 2Ag(s) Zn(s) + Cd 2+ (aq) Zn 2+ (aq) + Cd(s) (i) Deduce the order of reactivity of the four metals, cadmium, nickel, silver and zinc and list in order of decreasing reactivity. (ii) Identify the best oxidizing agent and the best reducing agent. (Total 4 marks)

13 SEMANA 3: 1. What condition is necessary for the electroplating of silver, Ag, onto a steel spoon? A. The spoon must be the positive electrode. B. The silver electrode must be the negative electrode. C. The spoon must be the negative electrode. D. The electrolyte must be acidified. 2. What is the reducing agent in the reaction below? 2MnO 4 (aq) + Br (aq) + H 2 O(l) 2MnO 2 (s) + BrO 3 (aq) + 2OH (aq) A. Br B. BrO 3 C. MnO 4 D. MnO 2 3. Consider the following standard electrode potentials. Cr 3+ (aq) + 3e Cr(s) Fe 3+ (aq) + e Fe 2+ (aq) E O = 0.74 V E O = V What will be the cell potential, in V, of a voltaic cell in which the following reaction takes place? A B C D Cr(s) + 3Fe 3+ (aq) 3Fe 2+ (aq) + Cr 3+ (aq)

14 4. A voltaic cell is made by connecting two half-cells represented by the half-equations below. Mn 2+ (aq) + 2e Mn(s) Pb 2+ (aq) + 2e Pb(s) E O = 1.19 V E O = 0.13 V Which statement is correct about this voltaic cell? A. Mn is oxidized and the voltage of the cell is 1.06 V. B. Pb is oxidized and the voltage of the cell is 1.06 V. C. Mn is oxidized and the voltage of the cell is 1.32 V. D. Pb is oxidized and the voltage of the cell is 1.32 V. 5. Fertilizers may cause health problems for babies because nitrates can change into nitrites in water used for drinking. (i) Define oxidation in terms of oxidation numbers. (ii) Deduce the oxidation states of nitrogen in the nitrate, NO 3, and nitrite, NO 2, ions. (Total 2 marks) 6. Nitric acid reacts with silver in a redox reaction. Ag(s) + NO 3 (aq) + Ag + (aq) + NO(g) + Using oxidation numbers, deduce the complete balanced equation for the reaction showing all the reactants and products. (Total 3 marks) SEMANA 4: 1. An electrochemical cell is made from an iron half-cell connected to a cobalt half-cell:

15 The standard electrode potential for Fe 2+ (aq) + 2e Fe (s) is 0.45 V. The total cell potential obtained when the cell is operating under standard conditions is 0.17 V. Cobalt is produced during the spontaneous reaction. (i) (ii) (iii) (iv) Define the term standard electrode potential and state the meaning of the minus sign in the value of 0.45 V. Calculate the value for the standard electrode potential for the cobalt half-cell. Deduce which species acts as the oxidizing agent when the cell is operating. Deduce the equation for the spontaneous reaction taking place when the iron half-cell is connected instead to an aluminium half-cell. (3) (v) Explain the function of the salt bridge in an electrochemical cell. (Total 9 marks) 2. Definir el ácido términos y base de acuerdo con la teoría de Bronsted-Lowry y estado de un ejemplo de un ácido débil y un ejemplo de una base fuerte Describe dos métodos diferentes, uno químicas y uno física, aparte de medir el ph, que podría ser utilizado para distinguir entre el ácido etanoico y soluciones de ácido clorhídrico de la misma concentración [4] 4. Black coffee has a ph of 5 and toothpaste has a ph of 8. Identify which is more acidic and deduce how many times the [H + ] is greater in the more acidic product

16 5. In an experiment conducted at 25.0 C, the initial concentration of propanoic acid and methanol were 1.6 mol dm 3 and 2.0 mol dm 3 respectively. Once equilibrium was established, a sample of the mixture was removed and analysed. It was found to contain 0.80 mol dm 3 of compound X. (i) Calculate the concentrations of the other three species present at equilibrium. (3) 6. Ammonia, NH 3, is a weak base. It has a pk b value of Calculate the ph of a mol dm 3 aqueous solution of ammonia at 298 K (Total 4 marks) 7. (i) 25.0 cm 3 of mol dm 3 hydrochloric acid solution is added to 50.0 cm 3 of mol dm 3 aqueous ammonia solution. Calculate the concentrations of both ammonia and ammonium ions in the resulting solution and hence determine the ph of the solution.

17 (5) (ii) State what is meant by a buffer solution and explain how the solution in (i), which contains ammonium chloride dissolved in aqueous ammonia, can function as a buffer solution. (3) [8] 8. Salts may form neutral, acidic or alkaline solutions when dissolved in water. (i) Explain why a solution of sodium chloride is neutral but sodium carbonate forms an alkaline solution when it dissolves in water.