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Chemistry 101 > Topic 4 > Flashcards

Topic 4 Flashcards

1
Q

Describe:

Photosynthesis with equation.

A

Is an endothermic process as there is a net absorption of energy where Light energy is absorbed by chlorophyll and stored as chemical energy in carbohydrates, given the equation:
6CO2(g) + 6H2O(l) =(energy)= C6H12O6(s) (Delta) H = +2802 kJ mol^-1

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2
Q

Explain:

How Chemical energy in carbohydrates can be accessed

A

Through respiration and combustion, chemical energy within bonds of long carbon chains are broken.

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3
Q

Describe:

Aerobic respiration with equation:

A

Series of reactions releasing energy in carbohydrates, an exothermic process as a net release of energy and is used for metabolic activity through equation:
C6H12O6(s) + 6O2(g) == 6CO2(g) + 6H2O(l) (Delta)H= -2802 KJ mol^-1

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4
Q

Describe and compare the uses of:

Carbon based fuels

A

Fossil fuels and biofuels, are able to undergo combustion with an oxidiser releasing energy stored in covalent bonds for electricity/transport. Fuels are also feedstock for consumer products or their production for paint/textile.

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5
Q

Describe:

Fossil fuels

A

Formed through decay of organic matter under metamorphic conditions. Coal, petroleum, natural gas. Non-renewable as they are used faster than they are formed.

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6
Q

Describe:

Biofuels

A

Derived from biomass, biodiesel, bioethanol, biogas. Are renewable as they are formed quick

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7
Q

Explain Advantages in terms of:

Fossil fuel reserves and infrastructure:

A

Coal, oil, gas reserves are relatively abundant
Developed infrastructure distributes fossil fuel to generate electricity, power internal combustion engines, produce products associated with petrochemicals.

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8
Q

Explain Advantages:

Fossil fuel extraction and energy density

A

Easily extracted/distributed though drilling, then through pipelines.
Combustion releases large energy per gram thus effective for production and transportation.

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9
Q

Explain Disadvantages:

Fossil fuel reserves, production and combustion

A

Rate of combustion is more than rate of formation. They are non-renewable as production.
Combustion results in much carbon dioxide, contributing to global warming. Also soot for air pollution leading to illness. Temperature leads to oxides of nitrogen for photochemical smog. Oxides of sulfur as impurities lead to acid rain.

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10
Q

Explain Advantages:

Biofuel Reserves, Production.

A

Reserves are plentiful, can be grown in short time. Production, as renewable they are derived from crops. 2nd gen are non-food biomass, 3rd gen are algae making a range of products.

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11
Q

Explain Advantages:

Biofuel energy density, products of combustion.

A

Provide energy density comparable to fossil fuel.
Is carbon neutral as emissions of CO2 from combustion is offset by absorbtion of CO2 by biofuel crops/microbes through photosynthesis.

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12
Q

Describe Disadvantages

Biofuel production, Product of combustion, Infrastructure

A

1st gen competes with land use of agriculture, for food production.
CO2 is still emitted, contributing to global warming. Oxides of nitrogen are produced contributing to photochemical smog.
Limited production/distribution of biofuel. Few manufactures design motors specifically for biofuel. Infrastructure not widespread for production/use of biofuel.

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13
Q

Detail:

Contributions to global warming of Fossil fuels, Biofuels

A

GHG released through extraction, processing, burning of FF. CO2 released in electricity production and combustion of FF.
Farming burns FF through production, processing, transportation. BF production uses electricity derived from combustion.

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14
Q

Detail:

Contribution to global warming of renewable energy sources

A

Hydropower, wind, solar do not directly generate GHG, however construction, maintenance, infrastructure require input of energy from FF.
Geothermal directly emits methane, carbon into troposphere.

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15
Q

Describe:

Production of bioethanol with equations:

A

Through anaerobic Fermentation of carbohydrates derived from vegetation given.
C6H12O6(aq) =(enzyme)= 2 C2H5OH(l) + 2CO2(g)
Polysaccharides go through hydrolysis to form monosaccharide for fermentation given:
(C6H10O5)n(aq) + nH2O =(enzymes)= nC6H12O6(aq)
C12H22O11(aq) + H2O = 2 C6H12O6
Higher concentrations are obtained through fractional distillation

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16
Q

Describe:

Production of biodiesel with equations:

A

Derived from triglycerides from plants/algae, through Transesterification, conversion of carboxylic acid in one ester into another. Methanol mixed with catalyst (strong base) and react with triglyceride, producing methyl esters given:
Triglyceride + Methanol =(Base catalyst)= Mix of fatty acid esters + glycerol

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17
Q

Describe:

Combustion

A

Reaction between fuel and oxdiant, exothermic. Complete combustion has enough moles of oxygen available to convert all carbon atoms into carbon dioxide, equation to combust can have half oxygens eg.
C8H18(l)+(25/2)O2(g) = 8CO2(g) + 9H2O(l) (Delta)H=-xxx KJ mol^-1

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18
Q

Explain:

equation; 1371 KJ heat released one mole of bioethanol undergoes combustion: give equation

A

C2H5OH(l) + 3O2(g) == 2CO2(g) + 3H2O(l) (Delta)H = -1371 KJ mol^-1

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19
Q

Expain:

Why incomplete combustion is more likely with long chains.

A

As length of chin increases or saturation decreases the ratio of carbon to oxygen increases, limiting O2 available, resulting in partially oxidised carbon, CO or Soot (aggregate if carbon nanoparticles), given eq
C8H18(l) + (17/2)O2(g) = 8CO2 + 9H2O(l)
C8H18(l) + (9/2)O2(g) = 8C + 9H2O(l)

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20
Q

Discuss:

Undesirable products of incomplete combustion.

A

Carbon monoxide binds to haemoglobin, decreasing oxygen carrying capacity in blood.
Soot, aggregate of carbon nanoparticles, limits visibility, covers plants limiting photosynthesis, causes respiratory issues, contribute to global warming.

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21
Q

Describe:

Molar enthalpy of combustion and values of Qmcatn and include total equation.

A 
Represents quantity of heat released per mole of fuel going through combustion in units of J.
Q = quantity of heat transferred
(Delta)H = molar enthalpy of combustion
m=Mass of liquid heated
C = specific heat capacity of the solvent
(Delta)T= Temperature change of solvent
N = moles of fuel that underwent combustion.
Given equation (Delta)H = (m c AT)/1000 n
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22
Q

Explain:

Determination of enthalpy of combustion

A

Through Calorimetry. A burner under can of water with thermometer.

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23
Q

Explain:

Energy conversions between, molar enthalpy, specific energy and energy density to compare fuels.

A

(KJ/mol) x M^-1 == (KJ/g) x g/L[density of fuel] == (KJ/L)

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24
Q

Describe:

Solar cells and fuel cells in electricity production and downsides.

A

Photovoltaic cells, convert sunlight into electricity through electron photon absorption to generate current, production of cells emit CO2.
Galvanic cells use spontaneous redox reactions to make current, chemical energy into electrical energy.

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25
Q

Detail:

Galvanic cell: cathode reaction, sign of anode, cation movement.

A

Reduction
Negative
Cathode

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26
Q

Describe and give half equations:

Proton exchange membrane

A

Hydrogen goes into anode, oxidises, proton goes though proton exchange membrane to cathode, electrons forced through external circuit to coming with protons and O2 molecules in cathode.
Anode: H2 = 2H+ + 2e-
Cathode: O2 + 4H+ + 4e- = 2H2O
Overall: 2H2 + O2 = 2H2O

27
Q

Describe:

Advantages/Disadvantages of Proton Exchange Membrane to galvanic cells. Then to fossil fuels.

A

Hydrogen is abundant fuel source, can last for ages, output is consistent.
Hydrogen may be obtained from fossil fuel. Electrodes easily contaminated. Metal catalysts expensive. Limited infrastructure.
Few atmospheric pollutants. Silent during operation.

28
Q

Describe:

Flow cells and advantages against fuel cells.

A

Is a rechargeable fuel cell, where positive and negative electrolyte is stored and pumped back when needed.
Virtually unlimited capacity. No emissions. Components can be laid in various configurations.

29
Q

Describe:

Coagulation

A

Colloids (fine particles suspended in water due to like charges) are neutralised through salts of aluminum which hydrolyse in water to make positive metal complexes in coagulation, neutralising negative charge on clay. Dispersion forces allow particles to aggregate into microfloc.

30
Q

Describe:

Flocculation.

A

Formation of larger floc, through agitation or addition of polymers which neutralise the surface charge and physically trap particles.

31
Q

Describe:

Hard water

A

Water with concentrations of Ca2+ and Mg2+ ions. This renders soap less effective. Causes build up of soap scum or precipitates which block pipes.

32
Q

Describe and explain:

Zeolites and its use

A

Hydrated aluminosilicate, linked alumina (AlO4) and silica (SiO4) tetrahedra, being negative charged acts as an exchangeable ion surface, where hard water cations are exchanged in equilibrium:
2Na+(z) +Ca2+(aq) ⇔ Ca2+(z) + 2Na+(aq)

33
Q

Describe:

Advantages and disadvantages of desalination.

A

Produces potable water, reduces demand of freshwater on its ecology, not reliant on climate and reliable production.
Energy intensive, expensive, results in waste of salts, kills fish in processing.

34
Q

Describe and explain:

Processes of desalination.

A

Thermal distillation, saline water boiled, vapor condensed and collected.
Reverse osmosis, semi permeable membrane to remove dissolved ions, molecules, pressure used to overcome osmotic pressure.

35
Q

Describe with equation:

Disinfection of water through chlorine and effect of pH

A

Chlorine gas, added to water, reacting establishing equilibrium, formation of HClO and HCl.
Cl2(g) + 2H2O(l) = HClO(aq) + Cl-(aq) + H3O+(aq)
According to le chateliers principle, addition of base like NaOH will increase hypochlorous acid.
Is used in water softening, to remove metal ions.

36
Q

Describe with equation

Disinfection of water through hypochlorites and effect of pH

A

Hypochlorite salts form hypochlorous acid in water given:
NaClO(s) + H2O(l) ⇔ HOCl(aq) + Na+(aq) + OH-(aq)
Addition of acid will reduce hydroxide ion concentration, le chatiliers principle says to counter change, eqilibrium wil shift to favor forward response, making more hypochlorous ions.

37
Q

Explain:

Why plants need nutrients in soluble form.

A

Mass-flow and Diffusion is how nutrient ions are taken into the root system. Mass-flow as nutrients are taken with the water from soil during transpiration. Ions in direct contact diffuse through concentration gradient.

38
Q

Describe:

The nitrogen cycle’s process of lightning.

A

.Lightning provides energy sufficient to convert nitrogen in the air given:
N2(g) + O2(g) = 2NO(g)
Which is oxidised.
2NO(g) + O2(g) = 2NO2(g)
Combines with water vapor/rain making nitric/nitrous acid
2NO2(g) + H2O(l) = HNO2(aq) + HNO3(aq)
Which then further ionise to form soluble nitrate/nitrite ions
HNO3(aq) + H2O(l) = H3O(aq) + NO3(aq)
HNO2(aq) + H2O(l) = H3O(aq) + NO2(aq)

39
Q

Describe:

The nitrogen cycle’s process excluding lighting.

A

Ammonification (decay), through decomposition of organic matter nitrogen is removed from amino acids/proteins forming into ammonia(NH3)/ammonium(NH4). Aerobic decom gives nitrate ions (NO3)
Nitrification, nitrifying bacteria convert ammonia into nitrite/nitrate ions
NH3/NH4 = NO2 = NO3

40
Q

Explain:

Why fertilizers are required to improve productivity of soils.

A

Nutrient deficient soils require fertilisers containing essential nutrients, nitrogen/phosphorus/potassium. Global food production necessitates arable land

41
Q

Explain:

Process of eutrophication

A

It is the increased nutrient concentration in the environment/body of water through human activity/rock weathering. Stimulating growth of microbes into Bloom, keeping sunlight/O2 from getting in, bloom uses O2

42
Q

Explain:

Consequences of eutrophication.

A

Anaerobic bacteria produce toxic product though decay, fish species may die, decrease in diversity.

43
Q

Describe:

Components of rocks and soils and normal charge of units.

A

Mostly silicates and aluminosilicates. Based off SiO4 tetrahedral unit. Aluminosilicates have Al in Si place.
Ca(2+) Si(4+) Al(3+)

44
Q

Describe;

Anion formula of silicates.

A

Anions are counterbalanced by metal cations/anions/uncharges species. thi s is the section that includes (Al)SiO. Its charge is identified by counting up all other charges.

45
Q

Describe:

Cation exchange in soils:

A

Occuring in equilibrium cations are adsorbed on surface of alumino/silicates, H+ ions are absorbed and would replace other cations.

46
Q

Explain:

Acidic or saline conditions in soil

A

Rock weathering/fertilisers change ph, shifting equilibrium acco. Le Chat. given eq.
3H+(aq) + Al3+(clay) ⇔ Al3+(aq) + 3H+(clay)
Leaving cations susceptible to leaching over rainfall.
Mg/Ca maintain flocculation in clays, binding layers. Sodium does not do that, weakening electrostatic attraction between layers.

47
Q

Describe:

Addition polymerisation and identification

A

Addition, reaction without loss of atoms, tending to have C=C double bond.
Polymer has continuous carbon backbone

48
Q

Describe:

Condensation polymer and identification.

A

Reaction with elimination of molecule (water). Can be polyester/polyamide. Ester has either hydroxycarboxylic or one dicarboxylic + one diol.
Amide(O=C-N-R)has either, aminocarboxylic acid or one dicarboxylic acid + one diamine.
Can be identified through amide/ester group. Monomer will need added H2O.

49
Q

Discuss:

Advantages and Disadvantages of synthetic polymers.

A

Offer range of structure/properties. Cheap manufacture/process. Equal, better to natural material.
Persist in environment, ingested by life. Limited recyclability. Take up landfill space. Leech harmful chemicals out, can be toxic if combusted.

50
Q

Discuss:

Organic polymer properties

A

Developed density, hardness, rigidity, conductivity. Molecular size increases strength of dispersion forces. Monomers determine, ester/amide link, hydroxyl/carboxyl/amino branch will experience Dipole-Dipole interaction/ H-bond between chain. Increase interaction strength/density/rigidity.

51
Q

Compare:

Effects of heating on thermoset and thermoplastics.

A

Thermo becomes fluid in heat, solid in cooling as there are no covalent crosslinking, secondary interactions are overcome by heat.
Thermoset has cross linking in polymers during curing as atoms of covalent bridges. Under heat, crack/char.

52
Q

Discuss:

Advantages and Disadvantages of polymer production from petrol.

A

Relatively abundant feedstock. Easily extracted and processed into chemicals. Existing infrastructure. Large ranger of polymers can be made
Non-renewable, being used faster than can be restored.

53
Q

Discuss:

Advantages and Disadvantages of polymer production from biomass.

A

Biomas is relatively abundant. Raw materials easily extracted and processes. Source of biomass may be by-products from other industry(farming). Is renewable.
Limited range of polymers derived. May compete with land cropped for food production.

54
Q

Explain:

Biodegradability of polymers, how?

A

Addition polymers are hard to break down due to strong C-C covalent bonds.
Degradables are designed to degrade after use. Through chemical reactions in environment, microorganisms, absorption of sunlight.

55
Q

Explain

How to tell if metal will be uncombined in nature

A

Low activity will result in being in a native form (uncombined).

56
Q

Explain:

Likely method of reduction for metal compound.

A

From most reactive to least: Molten electrolytic (6). Aqueous electrolytic(7).
Chemical reduction, CO as reducing agent(11)
O2 as reducing agent(Cu-Hg).
Found uncombined in nature(Ag-Au).

57
Q

Explain:

Method for conversion of mineral to metal.

A

Extraction: from what ore
Concentration: Crushed, waste removed (NA if % mineral high)
Conversion: Equations, processes to transfer into state for reduction (NA if already)
Reduction: Equations, electrolysis through molten/aqueous
Refining: Reactions to remove remains, may be allowed (NA if purity high)

58
Q

Explain:

Comparison of one method of reduction to another.

A

Thermal process requires much energy, combustion of fossil fuels. Electrolytic needs none of that.

59
Q

Describe:

In an electrolytic cell. Reaction at cathode. Sign of anode. Cation movement.

A

Reduction
Positive
To cathode

60
Q

Explain:

Advantages of recycling

A

Finite resources on earth may be reused. Reduces energy demands from extraction and processing of raw materials.

61
Q

Explain:

Difference in ease of recycling thermoplastic and thermoset polymers.

A

Thermoplastic may be cleaned, remodeled into new material through temperature as molecular chains may move freely before decomposition.
Degree of cross-linking increased, ease of recycling reduced. As it is heated, covalent cross links hold chains in fixed position, until decomposition by combustion.

62
Q

Explain:

Advantage of using composite materials.

A

Materials which complement eachother, improve properties offered by both.

63
Q

Explain:

Difficulties associated with recycling composite materials.

A

Heterogeneity of material makes it hard to seperate. Composites made from thermosetting polymer resin cannot be heated to seperate.
Mechanical, thermal, chemical methods used. Is limited due to costs, lower quality of separated components, lack of incentive, infrastructure.

Chemistry 101 (4 decks)

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