topic 11

Question 1

what is the symbol for a reversible reaction

Answer 1

–> <–

Question 2

what happens in the forward reaction of a reversible reaction

Answer 2

initially the reactants are used up quickly but then slow as their conc. drops

Question 3

what happenes in the backwards reaction of a reversible reaction

Answer 3

initially reactants are reformed slowly then speed up as the conc. of products increases

Question 4

what is dynamic equilibrium

Answer 4

rate of forwards reaction equals rate of backwards reaction in a closed system, conc. of each substance remains constant

Question 5

write a Kc equation for 2A + B –><– 2C + D

Answer 5

[A]^2 [B]

Question 6

how to calculate units of Kc

Answer 6

cancel out top and bottom of fraction
mol dm^-3
see flash card
invert powers if units under line

Question 7

what is homogeneous

Answer 7

all reactants and products in same state and all reactants and products in Kc

Question 8

what is herterogeneous

Answer 8

all reactants and products in different states and dont include solids and pure liquids in Kc

Question 9

2 NO2 (g) –><– 2NO (g) + O2 (g)
33.2 g NO2 heated in vessel with volume of 9.65 dm^3 at 450 degrees and 6.88g of O2 found in equilibrium mixture
calculate Kc

Answer 9

Initial moles
Change in moles
Equilibrium moles

see flash card

Question 10

CH3COOH (l) = C2H5OH (l) –><– CH3COOC2H5 (l) +H2O
at equilibrium conc, of ethanoic acid was 1,8 moldm-3 and ethanol was 3.2 moldm-3, Kc is 3.5 calculate conc. of products

Answer 10

see flash card
ans= 4.49 moldm-3

Question 11

what is total pressure

Answer 11

sum of all pressures of the individual gases (partial pressure)

Question 12

SO2Cl2 (g) –><– SO2 (g) + Cl2 (g)
at equlilibrium 263 KPa of Cl2, total pressure is 714 KPa
calculate partial pressure of SO2Cl2

Answer 12

188K
see flash card

Question 13

what is a mole fraction

Answer 13

proportion of gas in a mixture

Question 14

how to calculate a mole fration

Answer 14

number of moles of gas / total number of moles of gas in the mixture

Question 15

how to calculate partial pressure from mole fraction

Answer 15

mole fraction of a gas x total pressure in mixture

Question 16

3 moles of SO2Cl2 heated, eq\uilibrium mixture contains 1.75 moles of Cl2, total pressure = 714KPa , what is the partial pressure of SO2Cl2
SO2Cl2 (g) –><– SO2 (g) + Cl2 (g)

Answer 16

1. draw ICE table and write initial moles
2. we know we have 1.75 mol Cl2 at equilibrium
3. 1:1 ratio so change the same
4. mole fractiom of SO2Cl2
   1.25/4.75 = o.263
5. work out partial pressure
   0.263 x 7.14 = 188KPa

Question 17

write Kp expression for
eE (g) + fF (g) –><– gG (g) + hH (g)

Answer 17

Kp = (pG)^g (pH)^h
——————–
(pE)^e (pF)^f

Question 18

what is le chateliers principle

Answer 18

if a reaction is at equilibrium and is subjected to a change in pressue, temperature, or concentration, the position of equilibrium will move to counteract change

Question 19

what happens to the psoition of equilibrium if you increase conc. of reactant and conc. product

Answer 19

increase reactant = shift right, more product

increase product = shift left, less product

Question 20

what happens to the position of equilibrium is you increase pressure

Answer 20

shift to side with fewest number of gas particles

Question 21

what happens to the position of equilibrium is you increase temperature and decrease temp

Answer 21

increase = shift in endothermic direction +ve
decrease = shift exothermic -ve

Question 22

what happens to the position of equilibrium is you add a catalyst

Answer 22

nothing