ENERGY CHANGES

If salt is dissolve in water and the resulting solution feels cold to the hand. This implies that its

• Thermostatic

• Thermophilic

• Exothermic

• Endothermic

A catalyst increase the rate of a chemical reaction by providing a path that

• Raises the activation energy

• Increases the temperature

• Lowers the activation energy

• Increases the concentration

NH₄Cl_(aq) ⇋ NH_3(g) + HCl_(g)

The reaction above can only attain equilibrium if

• it is in a closed system

• it is in an open system

• One of the product is removed

• A gaseous reactant is added.

If an equilibrium reaction has ▵H

 $>$ 0, the reaction will proceed favourably in the forward direction at

• high temperature

• any temperature

• low temperature

• minimum temperature

In the reaction E + F ⇋ G + H. The backward reaction is favoured if the concentration of

• F is increased

• E is increased

• G is reduced

• E is reduced

PCl_5(g) ⇋ PCl_3(g) + Cl_2(g) in the reactions above, a decrease pressure will

• increase the yield of PCl₅

• Decelerate the reaction

• Increase the yield of PCl₃

• Accelerate the reaction

P_(g) + Q_(g) ⇋ 3R_(s) + S_(g) ▵H is negative, which of the following increase the yield of R?

• Using a larger closed vessel

• Increasing the temperature

• Removing some S

• Adding a positive catalyst

2SO_2(g) + O₂ ⇋ 2SO₃, ▵H = -189mol^-1 the equilibrium constant for the reaction above is increased by

• increasing the temperature of the system

• increasing the pressure of the system

• the addition of catalyst to the system

• increasing the surface area of the vessels

Equilibrium is said to be attained in reversible reaction when

• all reactants have been used up

• there is no further change in temperature

• the rate of the forward and backward reaction are equal

• all the products have been formed

Dynamic equilibrium describes a situation where

• a reaction give backs the reactants

• reactants are converted to products

• the concentration of reactants and products is equal

• both forward and reverse reaction proceed at the same rate