Beatty 14.3_EC_REVIEW(W3)_2023_Answers 1

1 Beatty Secondary School Science Department (Chemistry Unit) Chemistry 6092 Name: ___________________________________ ( ) Date: ________________ Class: 4E___ TOPIC: ENERGY CHANGES REVIEW Multiple-Choice Questions 1 Burning fuels such as methane is an exothermic process. CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (l) Which statement explains this fact? A Molecules release energy when they react. B More bonds are formed than are broken. C The bonds formed are weaker than the bonds broken. D That energy is released to the surroundings and maybe detected by an increase in temperature. ( D ) 2 In which equation is the sign of the energy change,  H, shown correctly? equation  H A 2AgCl (s) → 2Ag (s) + Cl2 (g) positive B CH4 (g) → C (g) + 4H (g) negative C H2O (l) → H2O (g) negative D CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (l) positive ( A ) 3 On combustion, which fuel never produces pollutants? A diesel B hydrogen C methane D petrol ( B ) 4 The energy profile diagram for a chemical reaction is shown. Which statement is correct? A The overall enthalpy change is equal to x + y. B The reaction is exothermic C The value of x would increase in the presence of a catalyst. D The value of y would decrease in the presence of a catalyst. ( B )

2 5 An equation for respiration is shown. C6H12O6 (s) + 6O2 (g) → 6CO2 (g) + 6H2O (g) ∆H = −2830 kJ/mol What can be deduced from the equation? A ∆H for photosynthesis is +2830 kJ/mol. B Energy from sunlight is needed for this reaction. C Respiration is only carried out by animals. D The equation shows the reaction between one volume of glucose and six volumes of oxygen to produce six volumes of carbon dioxide and six volumes of water. ( A ) 6 The equation for the combustion of hydrogen is shown. 2H2 (g) + O2 (g) → 2H2O (g) H−H O−H O=O bond energy in kJ/mol 436 463 498 What is the enthalpy change of this reaction? A −482 kJ/mol B −444 kJ/mol C +444 kJ/mol D +482 kJ/mol ( A ) 7 When steam is passed through excess hot coke a reaction occurs and the coke cools. C (s) + H2O (g) → CO (g) + H2 (g) The activation energy for the reaction is X. Which energy profile diagram for this reaction is correct? ( C )

3 8 The energy profile diagram for the reversible reaction, 2NH3 ⇌ N2 + 3H2, is shown. Which statements about this reaction are both correct? statement 1 statement 2 A Forward reaction is endothermic. The activation energy is different for the forward and reverse reactions. B Forward reaction is endothermic. The activation energy is same for the forward and reverse reactions. C Forward reaction is exothermic. The activation energy is different for the forward and reverse reactions. D Forward react