TOPIC 10 - EQUILIBRIUM I + II

Is one where no substances are added to or lost from the system.

When the rate of the forward reaction is equal to the rate of the reverse reaction and the concentration of the reactants and products remain in constant only reached in a closed system. - system will always go ahead to establish equilibrium. Reaction still continues even when quantity remains constant.

If dynamic eq. disturbed by a change in conditions the position of the equilibrium moves to counteract to oppose the change in the system.

• The reaction must be closed (i.e. nothing being added or removed) • The reaction must be reversible

• Pressure • Temperature • Concentration of reactants/products (material either added or removed) ALWAYS TALK ABT RATE OF REACTION and obtaining greater yield

Shifts to right to get rid of added reactants. So increase in yield (but not greatly if by-product formed). Opposite is reactants are removed, shifts to right to produce more reactants.

For reactions that involve gases Increase in press. shift equil to side with fewer molecules - moles to reduce the press in the system so it occupies a smaller volume. If same amount on either side, rate will be same and no equil. shift. For some reactions increase in pressure= darkening due to compressing molecules in a smaller volume

The equilibrium will move to the left (in the endothermic backwards direction) to lower the temperature. so syst. counteract by absorbing heat and problem is slow ROR. And decrease in yield.

Have NO EFFECT on equil. Catalyst will reduce time required to estabilish equil by lowering the activation energy. only increase ROR and also can lower energy costs catalysts increase the ROR without being chemically altered or used up in a reaction by lowering the activation energy of the reaction.

the concentration of products/concentration of reactants. - small letters = moles = [C]^c [D]^d / [A]^a [B]^b all [] is mol/dm3 when attempting it can make 1/mol/dm3 = dm3/mol show how far to the left or right the equilibrium is to the left/right Kc > 1 = forwards react dominates. productsproducts

A system in which there are at least two different states present. Catalyst diff state to the reactants.

A system in which everything is in the same physical state

Because their concentration is constant. Only works for homogeneous equilibria

Because they don’t affect the equilibrium concentrations of the products or reactants

3H2 + N2 —> 2NH3 - low temp = 450, high press = 200-100atm and iron catalyst. Need these conditions in order to maintain a greater yield, especially compromising temp maximises the yeild whilst ROR fast.

Stage 1: S (s) + O2(g) –>SO2 (g) not reversible Stage 2: SO2 (g) + ½ O2 (g) —> SO3 (g) ^H = -98 kJ mol-1 reversible - high press favour right side catalyst = V2O5 but slow rate and compromise temp used - give slightly better yield at a higher rate but high pressure - too high energy costs - good yield at high rates

CH2=CH2 (g) + H2O (g) —> CH3CH2OH(l) catalyst = concen H3PO4 p = 70 atm temp= 300 high pressure also leads to unwanted polymeriastion of ethene = polyethene

there are 2 rates of reaction lines A + B (reversible react)C + D - A+B reaction falls with time - C+D reaction increases (non-zero rate) = the 2 rates of react become equal

moles of reactant at equilib = initial moles - moles reacted moles of product at equilib = initial moles + moles formed CH3COOC2H5 + H20 = CH3COOH + C2H5OH n: 1 1 0 0 n at equilib: 0.7 0.7 0.3 0.3 c: 0.7/v 0.7/v 0.3/v 0.3/v v - total volume always then use Kc eq

N2 + 3H2 = 2NH3 n: 1.5 4.0 0 30% N reacted 0.3*1.5 = 0.45 moles formed n at equil: (1.5-0.45) (4-0.45*3) (0+0.45*2) times by n in eq c = n/v(1.5dm3) in Kc eq

of a gas in a mixture of gases is the pressure that the gas would exert if it alone occupied the volume of the mixture Kp - used for gas syst

mole fraction*total pressure Tp = p1 +p2 (no. of diff gases X mole fract = n of a gas/ total n of ALL gases

i. 1 0 0 c/f. 0.4 0.6 0.6 total n = 1.6 e. f/1.6 each gas individually Kp = Partial press reactant/ partial pressure of prod = f/1.6 * 6atm) each one and units in atm

i. 1 0 0 equil mole c/f. 0.4 0.6 0.6 total n = 1.6 e. f/1.6 each gas individually Kp = Partial press reactant/ partial pressure of prod = f/1.6 * 6atm) each one and units in atm - use eq to check mole ratio to find the equilibrium mole