Chemistry in Society

Question 1

bond enthalpies

Answer 1

the quantity of energy needed to break one mole of a bond in a gaseous molecule

measured in diatomic molecules (in data book)

Question 2

chromatography

Answer 2

a qualitative technique used to separate out the components of mixtures to help identify the chemicals present in a mixture

Question 3

dynamic equilibrium

Answer 3

acheived when the rates of the forward and reverse reactions are equal

the concentrations of reactants and products are constant (rarely equal)

Question 4

endothermic

reaction

Answer 4

reaction which absorbs heat from the surroundings

+ΔH

Question 5

enthalpy of combustion

Answer 5

the enthalpy change that occurs when one mole of a substance is burned completely in oxygen

Question 6

enthalpy of neutralisation

Answer 6

the energy change when acid is neutralised to form one mole of water

Question 7

enthalpy of solution

Answer 7

the energy change when one mole of a substance disolves in water

Question 8

exothermic

reaction

Answer 8

reactions which release heat into the surroundings

-ΔH

Question 9

feedstocks

Answer 9

• a reactant from which other chemicals can be extracted or synthesised
• they are derived from raw materials either by physical separation or by a chemical reaction

Question 10

hess’s law

Answer 10

the enthalpy change for a chemical reaction is independant of the route taken, so long as the start and end point are the same for both routes

Question 11

mean bond enthalpies

Answer 11

the quantity of energy needed to break bonds between gaseus atoms, averaged over different molecules that the bond can be found in

Question 12

molar volume

Answer 12

volume occupied by one mole of atoms in the gaseous state is the same for all gases (at a constant pressure and temperature)

l mol^-1

Question 13

oxidising agent

Answer 13

a substance which accepts electrons and is reduced in the process

Question 14

reducing agent

Answer 14

a substance which donates electrons and is oxidised in the process

Question 15

retention time

Answer 15

in gas chromatography, it is the time taken for an individual peak to pass through the column after the injection time

Question 16

specific heat capacity

formulae

Answer 16

E_h = cmΔT
can be used to find the enthalpy change of a reaction along with
ΔH = E_h/n

Question 17

standard solution

definition

Answer 17

a solution of accurately known concentration

Question 18

theoretical yield

Answer 18

the maximum possible amount of product in a reaction (if all the reactants have been converted into the product)

Question 19

titration

Answer 19

determines the volume of reactant solution required to react completely with the test solution

Question 20

volumetric analysis

Answer 20

using a standard solution in a quantitative reaction to determine the concentration of another substance

Question 21

factors influencing industrial process design

Answer 21

• availability, sustainability and cost of feedstock(s)
• opportunities for recycling
• energy requirements
• marketability of by-products
• product yield

Question 22

environmental considerations when designing industrial process

Answer 22

• minimising waste
• avoiding the use or production of toxic substances
• designing products which will biodegrade if appropriate

Question 23

standard solution

process

Answer 23

• calculate mass needed through molar calculations
• weigh out solid using weigh boat and mass balance
• transfer solid into a beaker (wash weigh boat 3 times)
• add deionised water and stir until solid is completely dissolved
• transfer into volumetric flask and wash beaker and glass rod 3 times
• fill flask so bottom of meniscus on line
• stopper flask and invert

Question 24

three types of chromatography

Answer 24

• paper chromatography
• thin layer chromatography
• gas chromatography

Question 25

factors which cause separation in chromatography

Answer 25

• size of molecule - the larger the molecule, the less it travels
• polarity of molecule - in a polar solvent, polar molecules will travel further as they are most attracted to the mobile phase

Question 26

gas chromatography

process

Answer 26

sample is injected into carrier gas which passes along a column to separate - substances with a greater affinity to the mobile phase will reach the detector more quickly whereas substances with greater affinity to the stationary phase will move more slowly through the column