D. Bond making is endothermic and releases energy. (Total 1 mark) Cu(s) + 2. D (Total 1 mark)

Transcription

1 1. Which statement about bonding is correct? A. Bond breaking is endothermic and requires energy. B. Bond breaking is endothermic and releases energy. C. Bond making is exothermic and requires energy. D. Bond making is endothermic and releases energy.. Consider the following reactions. Cu O(s) + 1 O (g) CuO(s) Cu O(s) Cu(s) + CuO(s) H O = 144 kj H O = +11 kj What is the value of H O, in kj, for this reaction? Cu(s) + 1 O (g) CuO(s) A B C D IB Questionbank Chemistry 1

2 3. Which types of reaction are always exothermic? I. Neutralization II. III. Decomposition Combustion A. I and II only B. I and III only C. II and III only D. I, II and III 4. A pure aluminium block with a mass of 10 g is heated so that its temperature increases from 0 C to 50 C. The specific heat capacity of aluminium is J g 1 K 1. Which expression gives the heat energy change in kj? A B C D IB Questionbank Chemistry

3 5. Which is true for a chemical reaction in which the products have a higher enthalpy than the reactants? Reaction H A. endothermic positive B. endothermic negative C. exothermic positive D. exothermic negative 6. Hydrazine is a valuable rocket fuel. The equation for the reaction between hydrazine and oxygen is given below. N H 4 (g) + O (g) N (g) + H O(g) Use the bond enthalpy values from Table 10 of the Data Booklet to determine the enthalpy change for this reaction. (Total 3 marks) 7. Methanol is made in large quantities as it is used in the production of polymers and in fuels. The enthalpy of combustion of methanol can be determined theoretically or experimentally. CH 3 OH(l) O (g) CO (g) + H O(g) IB Questionbank Chemistry 3

4 (a) Using the information from Table 10 of the Data Booklet, determine the theoretical enthalpy of combustion of methanol (3) (b) The enthalpy of combustion of methanol can also be determined experimentally in a school laboratory. A burner containing methanol was weighed and used to heat water in a test tube as illustrated below. The following data were collected. Initial mass of burner and methanol / g Final mass of burner and methanol / g Mass of water in test tube / g Initial temperature of water / C 1.5 Final temperature of water / C 6.4 IB Questionbank Chemistry 4

5 (i) Calculate the amount, in mol, of methanol burned. () (ii) Calculate the heat absorbed, in kj, by the water. (3) (iii) Determine the enthalpy change, in kj mol 1, for the combustion of 1 mole of methanol. () IB Questionbank Chemistry 5

6 (c) The Data Booklet value for the enthalpy of combustion of methanol is 76 kj mol 1. Suggest why this value differs from the values calculated in parts (a) and (b). (i) Part (a) (1) (ii) Part (b) (1) (Total 1 marks) 8. Consider the reaction between gaseous iodine and gaseous hydrogen. I (g) + H (g) HI(g) H O = 9 kj Why do some collisions between iodine and hydrogen not result in the formation of the product? A. The I and H molecules do not have sufficient energy. B. The system is in equilibrium. C. The temperature of the system is too high. D. The activation energy for this reaction is very low. IB Questionbank Chemistry 6

7 9. Under which conditions will the reaction between 1.0 g calcium carbonate and excess hydrochloric acid be the fastest? Assume that all reactions are carried out at the same temperature. A. One large piece of calcium carbonate and mol dm 3 hydrochloric acid B. One large piece of calcium carbonate and 1 mol dm 3 hydrochloric acid C. Powdered calcium carbonate and mol dm 3 hydrochloric acid D. Powdered calcium carbonate and 1 mol dm 3 hydrochloric acid 10. Which unit could be used for the rate of a chemical reaction? A. mol B. mol dm 3 C. mol dm 3 s 1 D. dm 3 hydrochloric acid IB Questionbank Chemistry 7

8 11. Which factors can affect reaction rate? I. The state of the reactants II. III. The frequency of the collisions between particles The average kinetic energy of the particles A. I and II only B. I and III only C. II and III only D. I, II and III 1. What is the equilibrium constant expression for the reaction below? NO (g) N O 4 (g) A. K c = B. K c = C. K c = D. K c = [NO [N [N O O [NO [N [NO [N [NO O O IB Questionbank Chemistry 8

9 13. On the axes below sketch two Maxwell-Boltzmann energy distribution curves for the same sample of gas, one at a temperature T and another at a higher temperature T. Label both axes. Explain why raising the temperature increases the rate of a chemical reaction (Total 5 marks) 14. (a) A solution of hydrogen peroxide, H O, is added to a solution of sodium iodide, NaI, acidified with hydrochloric acid, HCl. The yellow colour of the iodine, I, can be used to determine the rate of reaction. H O (aq) + NaI(aq) + HCl(aq) NaCl(aq) + I (aq) + H O(l) The experiment is repeated with some changes to the reaction conditions. For each of the changes that follow, predict, stating a reason, its effect on the rate of reaction. (i) The concentration of H O is increased at constant temperature. () (ii) The solution of NaI is prepared from a fine powder instead of large crystals. () IB Questionbank Chemistry 9

10 (b) Explain why the rate of a reaction increases when the temperature of the system increases. (3) (Total 7 marks) IB Questionbank Chemistry 10

11 1. A. C 3. B 4. D 5. A 6. bonds broken: 4 N H, N N, O=O / +0 (kj mol 1 ); bonds formed: 1 N N, 4O H / 801(kJ mol 1 ); 581 (kj mol 1 ); Award [3 for correct final answer. 3 [3 7. (a) amount of energy required to break bonds of reactants (kj mol 1 ) / 808 (kj mol 1 ); amount of energy released during bond formation of products (kj mol 1 ) / 3348 (kj mol 1 ); H = 540 (kj mol 1 ); 3 Award [3 for correct final answer. Award [ for (+)540. If old Data Booklet is used accept answer: 535 (kj mol 1 ) or award [ for (+)535. (b) (i) m(methanol) = ( ) = 0.53 (g); 0.53 g n(methanol) = 1 = (mol); 3.05 g mol Award [ for correct final answer. IB Questionbank Chemistry 1

12 (ii) T = ( ) = 4.9 (K); q = (mc T =) (J) / (kj); 0.41 (kj); 3 Award [3 for correct final answer. (iii) H O 0.41(kJ) c = / 5153 (J mol 1 ); (mol) = 5 (kj mol 1 ); Award [ for correct final answer. Award for (+)5 (kj mol 1 ). (c) (i) bond enthalpies are average values/differ (slightly) from one compound to another (depending on the neighbouring atoms) / methanol is liquid not gas in the reaction; 1 (ii) not all heat produced transferred to water / heat lost to surroundings/environment / OWTTE / incomplete combustion (of methanol) / water forms as H O(l) instead of H O(g) ; 1 Do not allow just heat lost. [1 8. A 9. C 10. C 11. D 1. D 13. IB Questionbank Chemistry

13 correctly labelled axes showing number of particles/frequency against (kinetic) energy; correctly shaped graph for T (curve must not touch or cross x axes); T curve to the right of T and with a peak lower than T; increasing the temperature increases the (kinetic) energy of the particles / more particles will possess the necessary activation energy; there will be more collisions per unit time / the frequency of collisions increases / there are more successful collisions; 5 [5 14. (a) (i) increases rate of reaction; molecules (of H O ) collide more frequently / more collisions per unit time; No ECF here. (ii) no effect / (solution) remains unchanged; solid NaI is not reacting / aqueous solution of NaI is reacting / surface area of NaI is not relevant in preparing the solution / OWTTE; (b) kinetic energy/speed of reacting molecules increases; frequency of collisions increases per unit time; greater proportion of molecules have energy greater than activation energy/e a ; Accept more energetic collisions. 3 max [7 IB Questionbank Chemistry 3