physical science/control test 7 nw/september 2022\nquestion 4\nconsider the decomposition reaction of…

physical science/control test 7 nw/september 2022\nquestion 4\nconsider the decomposition reaction of dinitrogen pentoxide:\n2 n₂o₅(g) → 2 n₂o₄(g) + o₂(g)\nthe table below shows the different energies for the above reaction.\n| heat of the reactants (hr) | 26.6 kj·mol⁻¹ |\n| activation energy (ea) | 6.73 kj·mol⁻¹ |\n| heat of the reaction (δh) | -7.28 kj·mol⁻¹ |\n4.1 define the term activation energy.\n4.2 is the above reaction endothermic or exothermic? give a reason for the answer.\n4.3 calculate the heat of the products.\n4.4 draw the potential energy versus course of reaction graph for the above reaction. on the graph indicate values for: heat of reactants (h reactants), heat of products (h products), energy at the activated complex, heat of the reaction (δh)\n4.5 on the same graph drawn in question 4.4, use a dotted line and draw the shape of the graph when a catalyst is added to the original reaction.

physical science/control test 7 nw/september 2022\nquestion 4\nconsider the decomposition reaction of dinitrogen pentoxide:\n2 n₂o₅(g) → 2 n₂o₄(g) + o₂(g)\nthe table below shows the different energies for the above reaction.\n| heat of the reactants (hr) | 26.6 kj·mol⁻¹ |\n| activation energy (ea) | 6.73 kj·mol⁻¹ |\n| heat of the reaction (δh) | -7.28 kj·mol⁻¹ |\n4.1 define the term activation energy.\n4.2 is the above reaction endothermic or exothermic? give a reason for the answer.\n4.3 calculate the heat of the products.\n4.4 draw the potential energy versus course of reaction graph for the above reaction. on the graph indicate values for: heat of reactants (h reactants), heat of products (h products), energy at the activated complex, heat of the reaction (δh)\n4.5 on the same graph drawn in question 4.4, use a dotted line and draw the shape of the graph when a catalyst is added to the original reaction.

Answer

Brief Explanations:

4.1 Activation energy is the minimum energy that reacting particles must have in order to undergo a chemical reaction. 4.2 The reaction is exothermic. The heat of reaction ($\Delta H$) is -7.28 kJ/mol. A negative $\Delta H$ value indicates that heat is released during the reaction. 4.3 We know that $\Delta H=H_{products}-H_{reactants}$. Rearranging for $H_{products}$, we get $H_{products}=\Delta H + H_{reactants}$. Substituting the given values: $H_{products}=-7.28\ kJ/mol+ 26.6\ kJ/mol = 19.32\ kJ/mol$. 4.4 To draw the potential - energy versus course of reaction graph: - Mark the heat of reactants ($H_{reactants}=26.6\ kJ/mol$) on the y - axis. - Since $\Delta H=-7.28\ kJ/mol$, the heat of products ($H_{products}=19.32\ kJ/mol$) is lower than the heat of reactants. - The activation energy ($E_a = 6.73\ kJ/mol$) is the energy difference between the reactants and the energy at the activated complex. Draw a curve starting from the reactants, rising to the activated complex (with the activation - energy height) and then dropping to the products. 4.5 When a catalyst is added, it lowers the activation energy. On the same graph, draw a dotted line with a lower peak (lower activation energy) than the original solid - line curve, while the heat of reactants and products remain the same.

Answer:

4.1 Activation energy is the minimum energy required for reacting particles to react. 4.2 Exothermic. Reason: $\Delta H=-7.28\ kJ/mol$ (negative value means heat is released). 4.3 $19.32\ kJ/mol$ 4.4 Graph should show reactants at 26.6 kJ/mol, products at 19.32 kJ/mol, and activation - energy of 6.73 kJ/mol with a curve connecting them. 4.5 Draw a dotted line on the graph with a lower activation energy peak while reactants and products energies are unchanged.