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Flashcards in Chemistry in Society Deck (53):
1

Industrial processes are designed to (maximise and minimise)?

Maximise Profit

Minimise Impact on the Environment

2

Factors influencing design include?

Sustainability and cost of feedstocksOpportunities for recyclingEnergy RequirementsMarketability of ByproductsProduct Yield

3

Environmental Considerations Include?

Minimising wasteAvoiding use/production of toxic substancesDesigning products which will biodegrade if appropriate

4

Balanced equations show (Unit 3)?

Mole ratio of reactants and products

5

n = (In terms of Mass)

m/GFM

6

n= (In terms of molar volume)

V/MV

7

Volumes of reactant and product gases can be calculated from?

The number of moles of each reactant and product

8

n = (In terms of concentration)

c x V

9

The efficiency with which reactants are converted into the desired product is measured in terms of?

The percentage yieldAtom Economy

10

Percentage Yield =

(Actual Yield x 100)/Theoretical Yield

11

Given costs for reactants, a percentage yield can be used to?

Calculate the feedstock's cost for producing a given mass of products

12

The atom economy measures?

The proportion of total mass of all the starting materials succesfuly converted into the desired products

13

Atom Economy = 

(Mass of Desired Products x 100)/ Total Mass of reactants

14

Reactions with a high percentage yield may have a low atom economy if?

Large quantities of unwanted products are formed

15

In order to ensure that costl reactants/feedstock are converted into products?

An excess of less expensive reactant/feedstock can be used

16

As many reactions are reversible products may be?

In equilibrium with reactants

17

Equilibrium may result in costly reactants?

Failing to be completely converted into products

18

In a closed system, reversible reactions attain a state of?

Dynamic equilibrium

19

What is dynamic equilibrium?

When the rates of forward and reverse reactions are equal

20

What happens to the concentrations of reactants and products at equilibrium?

Concentrations remain constant but are rarely equal

21

Manipulation of equilibria for profit

To maximise profits chemists employ strategies to move the position of the equilibrium to favour products

22

Le Chatelier's principle states?

An equilibrium will move to undo any change imposed upon it by temporarily favouring either the forward or reverse reaction until a new equilibrium position is reached

23

Le Chatelier's principle can be used to?

Predict the likely effects of altering pressure, altering temperature and addition/removal of reactants/products

24

Increasing the temperature of an equilibrium micture will favour?

The endothermic reaction

25

Decreasing the temperature of an equilibrium mixture will favour?

The exothermic reaction

26

If an equilibrium involving unequal numbers of moles of gas on either side the position will be affected by?

A change in pressure

27

In an equilibrium an increase in pressure will favour?

The reaction which produces fewer moles of gas

28

In an equilibrium a decrease in pressure will favour?

the reaction which produces more moles of gas

29

In an equilibrium increasing the concentration of a reactant will favour?

The forwards reaction

30

In an equilibrium decreasing the concentration of a reactant will favour?

The backwards reaction

31

Effect of catalyst on equilibrium

Increases the rate of attainment of the equilibrium but doesn't affect the position of equilibrium

32

The enthalpy of combustion of a substance is?

The enthalpy change when one mole of the substance burns completely in oxygen

33

Hess' Law states?

The enthalpy change for a chemical reaction is independent of the pathway taken

34

Bond enthalpies can be used to estimate the enthalpy change by?

Calculating the energy required to break bonds in reactants and energy released when new bonds are formed in the product

35

An oxidising agent is?

A substance which gains elecrons

36

A reducing agent is?

A substance which loses electrons

37

Elements with low electronegativity values tend to from positive ions so can act as?

Reducing Agents

38

Elements with high electronegativity values tend to form negative ions so can act as?

Oxidising agents

39

Where in the ECS are the strongest oxidising agents found?

Bottem Left (Come from group 7)

40

Where in the ECS do the strongest reducing agents come from?

The top right (Come from Group 1)

41

Examples of strong oxidising agents in acidic solution?

MnO4-  and Cr2O72-

42

Example of a molecule that can act as an oxidising agent

Hydrigen peroxide

43

Example of a molecule which can act as a reducing agent

Carbon Monoxide

44

Oxidising agents can be used to kill?

Bacteria and fungi

45

What does Chromatography do?

Seperates compounds according to their relative affinity for the mobile phase and the stationary phase

46

Predictors of solubility in the mobile phase

Size of molecules and their polarity

47

The stationary phase may be?

Paper, silica gel or inert packing material

48

The Rf value is?

The distance travelled by the sample divided by the distance travelled by the solvent

49

Retention time is?

The time it takes for the sample to move the full length of the stationary phase

50

Volumetric analysis involves?

Using a solution of accurately known concentration in a quantitative reaction to determine the concentration of another substance

51

What is a standard solution?

A solution of accurately known concentration

52

What is an indicator?

A substance which changes colour at the end-point of a reaction

53

Substance which acts as its own indicator?

Potassium Manganate(VII)  (potassium permanganate)