ACSBR 18 Energy Changes - Assignment ANS

Anglo-Chinese School (Barker Road) A Methodist Institution Founded in 1886 CHEMISTRY DEPARTMENT OF SCIENCE Name: ANSWERS ( ) Class: SEC 4 ENERGY CHANGES – ASSIGNMENT LIM POH FANG & ALEX LEE/2010 PAGE 1 OF 5 PURE/COMBINED Multiple-Choice Questions [20 Marks] TOTAL SCORE / 30 Write in your selected answer for the multiple-choice questions in the boxes provided. 1 2 3 4 5 6 7 8 9 10 D D B A C C A B B A 11 12 13 14 15 16 17 18 19 20 A D C C A C B D D D 1. Which of the following statements about an exothermic reaction is false? A The enthalpy change of the reaction is negative. B The reactants have higher energy than the products. C The reaction vessel increases in temperature. D The speed of reaction is greatest under low temperatures. 2. The dissolving of calcium chloride in water is an exothermic process. Which of the following graphs most accurately shows how the temperature of the reaction vessel varies with time? A C B D 3. Which of the following processes is exothermic? A boiling of water C photosynthesis B neutralisation D thermal decomposition temperature 25 °C time temperature 25 °C time temperature 25 °C time temperature 25 °C time

LIM POH FANG & ALEX LEE/2010 PAGE 2 OF 5 4. An endothermic reaction occurs when A ammonium chloride dissolves in water. B sodium reacts with water. C water at 0 oC changes to ice at 0 oC. D water is formed from hydrogen and oxygen. 5. Which of the following is an endothermic process? A The addition of water to anhydrous copper(II) sulfate. B The combustion of ethanol in air. C The formation of a carbohydrate and oxygen from carbon dioxide and water. D The oxidation of carbon to carbon dioxide. 6. Which of the following is a difference between endothermic and exothermic reactions? A Endothermic reactions have a negative enthalpy. B In endothermic reactions, light is always absorbed. C In exothermic reactions, bonds are formed. D In exothermic reactions, heat is always absorbed. 7. Which energy diagram best represents an exothermic reaction? A C B D 8. Which of the following statements is not true? A All chemical reactions involve an energy change. B Dissolving a salt in water is always an endothermic reaction. C Exothermic reactions usually involve bond formation. D When a chemical bond is broken, energy is absorbed. 9. Heat energy is given to the surroundings during A boiling B condensation C evaporation D melting energy progress of reaction reactants products energy progress of reaction reactants products energy progress of reaction reactants products energy progress of reaction reactants products

LIM POH FANG & ALEX LEE/2010 PAGE 3 OF 5 10. The formation of liquid water from hydrogen and oxygen occurs in three stages: Stage I: 2 H2 (g) + O2 (g) ⎯→ 4 H (g) + 2 O (g) Stage II: 4 H (g) + 2 O (g) ⎯→ 2 H2O (g) Stage III: 2 H2O (g)