C5

Question 1

Features of

equilibrium

Answer 1

-occurs in closed systems
-rate of foreword reaction decreases over time and rate of backwards reaction increases over time, until the
Rate of the forward reaction = rate of backward reaction
(Equilibrium)
-Concentration of all reacting substances stay constant

Question 2

What is equilibrium position?

Answer 2

The trend in reactions (Are most reactions backward or forward?)

Le Chateliers principle- change made to a reactions In equilibrium leads to a change of the equilibrium position, opposite to the change.

Question 3

Theoretical yield of product

Answer 3

Maximum amount of product that can be produced with the given quantities of reactants

Theoretical yield of product (g) = mass of limiting reactant (g)/ sum of Mr for limiting reactant x sum of Mr for product

Question 4

Factor affecting equilibrium position

Answer 4

Higher concentration of reacting substance-position moves away from the reacting substance

Higher temperature-position moves towards the endothermic reaction

Higher pressure-position moves in the direction of the fewest moles of reacting gas

Question 5

Percentage yield

Answer 5

The amount product actually produced relative to the theoretical yield

Percentage yield= actual yield/theoretical yield x 100

Question 6

Reasons for percentage yield not being 100%

Answer 6

• side reactions may take up by products
• reaction may not go to completion
• product lost during transfers and purification

Question 7

Atom economy

Answer 7

Amount of desired product (in atoms) relative to the total amount of products

Atom economy = sum of Mr of the desired product/sum of Mr of all products x 100

Question 8

Factors that need to be considered for a reaction pathway

Answer 8

-atom economy, absence/usefulness of byproducts, rate of reaction and equilateral position
Cost of reactants

Question 9

Titration

Answer 9

Technique used to find the concentration of an acid or alkali

Question 10

Reaction conditions

Answer 10

• for a reaction to happen, particles must collide
• particles must have activation energy or more
• higher frequency of successful collisions leads to higher rate of reaction

Question 11

Catalysts

Answer 11

• increase the rate of reaction without being used up themselves
• do this by lowering activation energy

Question 12

Concentration of solutions formula

Answer 12

Concentration (mol/dm3) = amount of solute (mol)/ volume of solution (dm3)

Question 13

Gas volume calculations

Answer 13

Volume of gas (dm3)=amount (mol)x Vm

Vm= molar volume =24 dm3/mol at rtp + surface air pressure

Question 14

What indicator is used in titration and what happens to it?

Answer 14

Phenolphthalein- turns pink over pH 9

Question 15

What effect does increasing pressure have on equilibrium position?

Answer 15

The equilibrium position moves in the direction of the fewer moles of gas.

Question 16

What effect does increasing the temperature have on equilibrium position?

Answer 16

The equilibrium position will move in the direction of endothermic energy change

Question 17

What effect does decreasing pressure have on equilibrium position?

Answer 17

The equilibrium position moves in the direction of more moles.

Question 18

What effect does decrease in Temperature have on equilibrium position?

Answer 18

The equilibrium position moves in the direction of the exothermic energy change

Question 19

How is a fraction in column used to separate fractions in crude oil?

Answer 19

• Tall column with condensers coming off at different heights
• Column heated at the bottom so hot at the bottom and cool, at the top
• Substances with high boiling points condense at the bottom
• Substances with low boiling points condense at the top