The volume of the container is now decreased to 2,50 dm 3, while the temperature is kept at a constant 600 C. How will each of the following be affected? Choose from INCREASES, DECREASES or REMAINS THE SAME. 5.1 The value of Kc. 5.2 The mass of Cl 2 (g) in the container.

6.5
6.5.1 The value of $K_c$.
The equilibrium constant $K_c$ is only affected by temperature. Since the temperature is kept constant at $600 \text{ °C}$, the value of $K_c$ will not change.
$\boxed{\text{REMAINS THE SAME}}$

6.5.2 The mass of $\text{Cl}_2(\text{g})$ in the container.
Decreasing the volume of the container increases the pressure. The equilibrium will shift to the side with fewer moles of gas.
Reactants: $4\text{HCl}(\text{g}) + \text{O}_2(\text{g})$ (5 moles of gas)
Products: $2\text{H}_2\text{O}(\text{g}) + 2\text{Cl}_2(\text{g})$ (4 moles of gas)
Since the product side has fewer moles of gas, the equilibrium will shift to the right, favoring the formation of products, including $\text{Cl}_2(\text{g})$.
$\boxed{\text{INCREASES}}$

6.6 Explain the answer to QUESTION 6.5.2 by referring to Le Chatelier's Principle.
When the volume of the container is decreased, the total pressure of the system increases. According to Le Chatelier's Principle, the equilibrium will shift in the direction that reduces the number of moles of gas to counteract this increase in pressure. In the given reaction, the product side has 4 moles of gas, while the reactant side has 5 moles of gas. Therefore, the equilibrium shifts to the right (towards the products), leading to an increase in the concentration and thus the mass of $\text{Cl}_2(\text{g})$.

6.7
6.7.1 Is the heat of the forward reaction, ($\Delta H$), POSITIVE or NEGATIVE?
The temperature was increased, and the value of $K_c$ increased from 81 (from previous context) to 450. An increase in $K_c$ indicates that the equilibrium shifted to the right (towards products). According to Le Chatelier's Principle, an increase in temperature favors the endothermic reaction. Therefore, the forward reaction is endothermic.
$\boxed{\text{POSITIVE}}$

6.7.2 Explain the answer to QUESTION 6.7.1 by referring to Le Chatelier's Principle.
When the temperature of the container is increased, the equilibrium shifts to counteract this change. Since the value of $K_c$ increased, it indicates that the equilibrium shifted to the right, favoring the formation of products. According to Le Chatelier's Principle, an increase in temperature favors the endothermic reaction (the reaction that absorbs heat). Therefore, the forward reaction must be endothermic, meaning its heat of reaction ($\Delta H$) is positive.