Acertain reaction has an equilibrium constant of 3.5 × 108 at 25°c and 6.0 × 10–2 at 500°c. is the reaction exothermic or endothermic?

The reaction is exothermic.

Explanation:

When the temperature changes in a balanced system, it ceases to be in equilibrium because the value of the equilibrium constant is modified. Thus, at a temperature T1 the constant is K1, and at a temperature T2, the constant is K2. The relationship between these magnitudes is given in the so-called Van't Hoff equation.

The Wan't Hoff equation is:

Where:

ΔH: standard enthalpy of the reaction

R: constant of ideal gases

K1: equilibrium constant at temperature T1

K2: equilibrium constant at temperature T2

The Van't Hoff equation allows us to study how the chemical equilibrium shifts with temperature depending on whether we have an endothermic or exothermic reaction. So if the reaction is exothermic, ΔH <0, increasing the temperature decreases the equilibrium constant and the reaction moves to the left, while if the temperature decreases, the equilibrium constant increases and the equilibrium moves to the right.

Therefore, given the values of the equilibrium constant at different temperatures and observing that it decreases when the temperature rises, the reaction is exothermic.

when [oh-] is 10-5  m, and [h3o+] is 10-9  m, the poh is 5 and ph is 9. again in both cases the sum of ph and poh is 14. however, the hydrogen ion concentration is not always going to be equal to exactly 1 x 10 raised to a negative number. for example, we skipped over the value of 2.0 x 10-7.