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chemistry semester 2 (2022) > Chemistry Synthesis > Flashcards

Chemistry Synthesis Flashcards

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1
Q

Give a summary of Ethyl Ethanoate
(Essential Chem: SET 18: Q11)

A
  • Is an example of a multi-step reaction
  • Ethene is reacted with steam to produce ethanol and then is reacted with acetic acid (CH3COOH) to produce ethanoic acid and then another ethanol (through the reaction of ethene + H2O (steam) is then reacted with ethanoic acid to form Ethyl Ethanoate
  • The ester formation uses convergent pathway
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2
Q

Rate & Yield
———————

Define the following:
- Yield
- Catalyst
- Rate
- Equilibrium

A

Yield: Actual amount of products formed from reaction
Catalyst: An alternate reaction where it speeds up the reaction with a lower activation energy. It increases desired product in less time & doesn’t increase yield.
Rate: Measures how much product produced in given time period as per hour or per day
Equilibrium: The extent of a reaction measures proportion of reactant to the product. This can be stated as a % yield. Relates to equilibrium constant - high kinetic energy means lots of products

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3
Q

Rate & Yield
———————
Give a summary on rate and yield affected by the following actions:
- addition of reactants to mixture
- Removing products as they form
- Increase pressure of gases in case of reaction involving gases
- Adding catalyst
- Increasing surface area of a solid reactant or of a catalyst (can also apply to a liquid reactant)
- Increasing temp.

A

(Revise on booklet)

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4
Q

Rate & Yield
——————-

Describe other factors to consider in increasing yield + rate

A
  • Costs + risks associated w/ operating at high or low pressures since both require stronger vessels, pipes & pumps
  • Energy costs of operating at higher temps.
  • Hazards + risks associated w/ raw materials
  • Management of any wastes has disposal needs (e.g. gases, liquids & solids)
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5
Q

Polymers
—————
Draw a formation of polyethene

A

(In booklet)

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6
Q

Polymers
—————
Give a summary of low density polyethene and high density polyethene and their properties & uses

A

Low density polyethene:
-Produced using high temperatures
- Have short branches off main chain
- Dispersion forces are weak
- Properties: soft, flexible, low melting point, non-crystalline & non-conductors of electricity
- Uses: plastic bags, containers, waterproof layers in milk cartons

High density polyethene:
- Produced using low temperatures
- Have very few branches of main chain
- Properties: Hard, high b.p., crystalline & non-conductors of electricity
- Uses: plastic water bottles, food storage containers, water pipes and fuel tanks

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7
Q

Polymers
—————
What are the properties of teflon?

A

Properties:
- Non-stick
- Heat resistance
- Chemical resistance
- Good mechanical properties
- Low friction coefficient
- Flame resistance

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8
Q

Polymers
—————
What are the properties & uses of nylon?

A

Properties:
- High mechanical strength, stiffness, hardness & toughness
- Good fatigue resistance
- High mechanical dampening ability

Uses:
- Women’s stockings
- Materials in swim wear
- Parachutes

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9
Q

Polymers
—————
- What are the properties & uses of PET (Polyethene terephthalate)

A

Properties:
- Very strong and lightweight
- Known for good gas and moisture properties
- Is recyclable

Uses:
- plastic bottles
- microwaveable containers
- Textiles

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10
Q

Biodiesel
—————
What is biodiesel?

(Set 21: Q4-13)

A
  • Fuels that are organic compounds containing mostly carbon and hydrogen. When combusted they produce large amounts of energy, along with CO2 and H2O as primary products.
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11
Q

Biodiesel
—————
Where are biodiesel produced from?

(Set 21: Q4-13)

A
  • Plant
  • Animal material
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12
Q

Biodiesel
—————
What is produced when sugars are fermented and what is it used for?

(Set 21: Q4-13)

A

It produces ethanol and is used as a fuel.

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13
Q

Biodiesel
—————
Describe diesel and draw it’s molecule

(Set 21: Q4-13)

A
  • Diesel is a hydrocarbon with chain length around 8-21 carbons
  • Biodiesel has a modified structure with an ester group due to it’s source being a triglyceride
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14
Q

Biodiesel
—————
What are the advantages and disadvantages of lipases over bases?

(Set 21: Q4-13)

A

Advantages:
- Operate at mil temp. & pH
- Don’t cause side reactions
- Less energy required
- Catalyse 2 reactions at the same time

Disadvantages:
- Slower acting
- Higher concentration of enzymes needed
- More $$$
- Hard to recover lipase from final mixture

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15
Q

Contact Process
————————
Give summary of Contact Process and what processes are used?

A
  • C.P is multi-step process of synthesising sulfuric acid. All steps are designed to minimise waste, side reactions and undesired products. All steps are energy efficient and catalysts are used to reduce energy use.
  • This process uses raw materials such as sulfur, water and oxygen in a reaction sequenced involving up to 5 separate chemical reactions
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16
Q

Contact Process
————————
Explain the 3 main steps in Contact Process (include equations)

A
  1. Production of sulfur dioxide
    S(l) + O2(g) —> SO2(g)
  2. Conversion of sulfur dioxide to sulfur trioxide by reacting it with oxygen
    2SO2(g) + O2(g) —><— 2SO3(g)
  3. Conversion of sulfur trioxide to sulfuric acid by dissolving sulfur trioxide in concentrated sulfuric acid before reacting w/ water
    (Indirectly absorbing SO3(g) into H2SO4(l)
17
Q

Contact Process
————————
Where does the compromise occur in this process and why?

A
  • C.P involves industrial compromise in second step. As the ideal temp. Is low but this lowers the rate of reaction, so the reaction occurs at a temperature that is a compromise between the two.
18
Q

Contact Process
————————
Give a summary of conditions of C.P on how increased temp, increased pres, and catalysts affects the equ. Yield, reaction rate and actual conditions used in C.P

A

Increased temperature:
- Effect in eq. Yield = decreases
- Effect on reaction rate = increases
- Actual conditions used = Approx 400 degrees Celsius

Increased pressure:
- Effect in eq. Yield = increases
- Effect on reaction rate = increases
- Actual conditions used = 1-2 Atm pressure

Catalyst present:
- Effect in eq. Yield = no effect
- Effect on reaction rate = increases
- Actual conditions used = Porous pellets of vanadium (V) oxide

19
Q

Soaps & Detergents
——————————
Give a brief summary about soaps

A
  • Soap is made when ester hydrolysis occurs: where heating of an ester w/ strong base (NaOH) —> hydrolysis. This converts the ester to original alcohol an carboxylic acid from which is was added, but the presence of a strong n .base in reaction means that the carboxylic acid will be in a form of a salt.
  • Soaps consists of fatty acids with a long non-polar chain and a polar carboxylate at the other end
  • The soap is bonded to a potassium or sodium ion, making final structure a potassium or sodium carboxylate salt
20
Q

Soaps & Detergents
—————————-
Describe the structure of soap

A
  • Soap’s ability to clean things are associated with their non-polar hydrocarbon chain w/ a highly polar ionic group.
  • It’s ionic end is hydrophilic (meaning water attracting) while the non-polar hydrocarbon chain is hydrophobic (no attracted to water).
  • The ionic hydrophilic end is commonly associated with carboxylic acid whilst non-polar hydrocarbon chains that are hydrophobic are commonly associated with alcohols
21
Q

Soaps & Detergents
—————————-
What are the structural differences between soaps and detergents? Include diagrams as examples.

A

Soaps:
- Ionic head is a carboxylate
- Has a straight hydrocarbon chain length

Detergents
- Ionic head is a sulfonate ion
- Hydrocarbon chain includes a benzene ring

22
Q

Soaps & Detergents
—————————-
How do soaps and detergents remove grease?

A
  • The non-polar hydrocarbon chains of soap and detergent ions form dispersion forces w/ grease which is soluble in the grease
  • The ionic heads aren’t soluble in grease but forms dipole forces with water and there become soluble in water
  • Non-polar chains dissolves into grease w/ ionic heads sitting on surface of the grease still in contact with polar water
  • The hydrophobic tails of soap ions are attracted to one another, this attraction coupled with hydrophilic ends of soap ions to water molecules (caused by ion dipole forces) cause soap ions and grease to form micelles
  • As non-polar grease is embedded inside micelle it is stabilised in water and repel each other due to negatively charged surfaces, preventing formation of larger lumps of insoluble grease.
  • Finally, micelles can then be washed away leaving clean surface
23
Q

Soaps & Detergents
—————————-
Brief summary of the process of Hard Water

A
  • Hard water is water containing ions that can’t lather with soap ions
  • A factor that prevents soaps and detergents to clean is due to presence of ions such as calcium and magnesium in water.
  • These ions react with soap ions and precipitation occurs forming insoluble substance resembling floating scum.
  • Synthetic detergents don’t form scum in hard water as calcium and magnesium sulfonates are soluble in water

chemistry semester 2 (2022) (2 decks)

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