Consider the following system at equilibrium where H° = -111 kJ, and Kc = 0.159 , at 723 K: N2 (g) + 3 H2 (g) 2 NH3 (g)

If the TEMPERATURE on the equilibrium system is suddenly decreased :

The value of Kc A. Increases B. Decreases C. Remains the same

The value of QcA. Is greater than Kc B. Is equal to Kc C. Is less than Kc

The reaction must: A. Run in the forward direction to restablish equilibrium. B. Run in the reverse direction to restablish equilibrium. C. Remain the same. Already at equilibrium.

The concentration of H2 will: A. Increase. B. Decrease. C. Remain the same.

The value of will increase.

The value of will decrease.

The reaction must run in the forward direction to re-establish equilibrium.

The concentration of hydrogen gas will decrease.

Explanation:

Any change in the equilibrium is studied on the basis of Le-Chatelier's principle.

This principle states that if there is any change in the variables of the reaction, the equilibrium will shift in the direction to minimize the effect.

As, enthalpy of the reaction is negative. So, it is an exothermic reaction.

For an exothermic reaction, heat is released during a chemical reaction and is written on the product side.

As, heat is released during a chemical reaction. This means that temperature is decreased on the reactant side. If the temperature in the equilibrium is decreased, the equilibrium will shift in the direction where, temperature is getting increased.

Thus, the reaction will shift in right direction that is towards the product to reestablish the equilibrium..

As the reaction will move in forward direction the value of will increase and the value of will decrease.

( Move in froward direction )

Since, the equilibrium will be shifting in forward direction the concentration of hydrogen gas will decrease.

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."

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