The diagram shows a proposed energy profile for the reaction between methane and oxygen. Methane is a carbon compound used as a fuel. Fig. 1 includes the ac...
Question 1 Report
The diagram shows a proposed energy profile for the reaction between methane and oxygen. Methane is a carbon compound used as a fuel. Fig. 1 includes the activation energy, labelled A, and the overall energy change, labelled B. The reaction produces carbon dioxide and water. A teacher asks students to link the graph to the breaking and making of chemical bonds.
(a) Give the name of arrow A. [1]
(b) Give the direction of arrow B: upward or downward. [1]
(c) Use Fig. 1 to state whether combustion of methane is exothermic or endothermic. [1]
(d) Describe what happens to bonds during the rise to the peak. [1]
(e) Describe what happens to energy when bonds in carbon dioxide and water form. [1]
(f) Give one reason why methane combustion needs a spark or flame to start. [1]
Answer Details
(a) Arrow A is the activation energy, the minimum energy needed for reaction to start. [1]
(b) Arrow B is downward, from the reactants' energy level to the lower products' energy level. [1]
(c) Combustion of methane is exothermic because the products are at lower energy than the reactants. [1]
(d) On the rise to the peak, bonds in the reactants are broken and energy is taken in. [1]
(e) When bonds in carbon dioxide and water form, energy is released. [1]
(f) A spark or flame supplies the activation energy needed to start methane combustion. [1]
Download The App On Google Playstore
Everything you need to excel in your exams
