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Chemistry > Topic 5 - Separate chemistry 1 > Flashcards

Topic 5 - Separate chemistry 1 Flashcards

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1
Q

How can you calculate the molar volume of a gas

A

Molar volume = volume (dm^3) / moles of gas
Unit - dm^3 mol^-1

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2
Q

What is atom economy?

A

Measure of the efficiency of the reaction, looks at amount of reactants that get turned into useful products

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3
Q

How can you convert concentration from g dm^-3 to mol^-3?

A

Concentration (mol dm-3) = concentration (g dm^-3) / molecular mass (Mr)

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4
Q

How do you calculate the concentration of a solution in g dm^-3?

A

Concentration (g dm^-3)
= mass (g) / volume (dm3)

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5
Q

How do you calculate the concentration of a solution in
mol dm^-3?

A

Concentration (mol dm^-3)
= moles / volume (dm3)

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6
Q

Why might a specific reaction pathway be chosed over another

A
  • Higher atom economy
  • Higher yield
  • Faster rate
  • Equilibrium position favours products more
  • By-products are more useful or less harmful
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7
Q

What is the percentage yield of NH3if 40.5g of NH3 is produced from 20.0 mol H2 and excess N2?

A

Equation: N2+ 3H2 –> 2NH3
Moles of ammonia = 20/1.5 = 13.3 moles
Mass of ammonia = 13.3 x (14+1+1+!) = 227g
Percentage yield = (40.5/227 )x 100 = 17.8%

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8
Q

How do you convert concentration from g dm^-3 to mol dm^-3?

A

Concentration (g dm^-3) = concentration (mol dm^-3) x molecular mass (Mr)

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9
Q

What os the molar volume of a gas at room temperature and pressure?

A

The volume occupied by one mole of molecules of any gas at room temperature and pressure

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10
Q

Fill in the gap: ‘The ______ the atom economy, the more sustainable and efficient the process’

A

The higher the atom economy, the more sustainable and efficient the process

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11
Q

What is room temperature and pressure?

A

Room temperature - 20C
Room pressure - 1 atmoshpere

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12
Q

How do you calculate atom economy?

A

Atom economy = (Mr of desired product / Mr of reactants) x 100

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13
Q

How do you calculate percentage yield?

A

Percentage yield = (Actual yield / Theoretical yield) x 100

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14
Q

What does Avogadro’s Law state about gas volumes?

A

At the same temperature and pressure, equal amounts of gas will occupy the same volume

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15
Q

Why could the actual yield of product be less than the theoretical yield?

A
  • Incomplete reaction
  • Practical losses during experiment (e.g. some solid may get lost when being transferred between beakers)
  • Cometing, unwanted reactions (side reactions)
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16
Q

What is the haber process

A

Reversible reaction between nitrogen and hydrogen to form ammonia

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17
Q

What factors affect rate of attainment of equilibrium

A
  • Changes in temperature
  • Changes in pressure
  • Changes in concentration
  • Use of catalyst
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18
Q

How is rain of attainment of equilibrium affected by temperature

A
  • Higher temperature means equilibrium is reached quicker
  • This is because reacting particles have more kinetic energy so there are more frequent successful collisions
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19
Q

How is rate of attainment of equilibrium affected by catalyst

A
  • Equilibrium is reached faster when a catalyst is used
  • This is because catalyst provides an alternative reaction pathway with lower activation energy
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20
Q

What are typical properties of transition metals

A
  • High melting point
  • High density
  • Form coloured compounds
  • Transition metals and their compounds can be used as catalysts
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21
Q

What causes metals to corrode

A

Oxidation of metals

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22
Q

Why is corrosion of metal a redox reaction

A

Metal loses electrons so is oxidised and oxygen gains electrons so is reduced

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23
Q

What is rusting

Study These Flashcards
A

Corrosion of iron when it oxidises

24
Q

How can rusting be prevented

Study These Flashcards
A
  • Exclusion of oxygen
  • Exclusion of water
  • Sacrificial protection
25
How can oxygen and water be excluded to prevent iron rusting
* Paint metal * Coat metal in oil/greass * Cover metal in plastic * Keep metal in vacuum container
26
What is sacrificial protection
When metal being protected from rusting is galvanized with more reactive metal
27
How does sacrificial protection prevent corrosion
Outer metal will corrode first preventing corrosion of inner metal
28
Which metal is used in sacrificial protection of iron
Zinc
29
What is electroplating
When metal is coated with a layer of another metal
30
What are uses of electroplating
* To improve appearance of metal * Improve resistance of metal objects
31
What is process of electroplating something
* Metal being coated is cathode * Metal that will form exterior layer is anode * Electrolyte solution must contain ions of metal which will form outer coating * Power supply connected to both electrodes
32
What is an alloy
Mixture of two or more metals or metal and another element
33
How does converting a pure metal to an alloy increase the strength of product
* Allous contain several metals which will have different sized atoms * This distorts regular arrangement of atoms so layers are unable to slide over one another very easily
34
Why is iron alloyed with other metal to produce alloy steels
* iron is relatively brittle so is combined with other elements such as carbon to produce material with more desirable qualities * Low carbon steel - Malleable so used for sheeting * High carbon steel - Hard so used for cutting tools * Stainless steel - corrosion resistant so used for cutlery
35
What property of copper makes it suitable to be used in electrical cables
It is a very good electrical conductor
36
What property of aluminium makes it suitable for use in aircraft’s
Low density
37
What property of gold makes it suitable to be used in jewellery
* Very unreactive so resistant to corrosion * Jewellety appearance won’t be affected over time
38
What is magnalium and what is it used for
* It is an alloy of magnesium and aluminium * Lighter and stronger than aluminium and more resistant to corrosion * Used for cars and aircraft’s
39
What is brass and what is it used for
* Alloy of copper and zinc * It is hard and resistant to corrosion * Used for decorative hardware.
40
41
How is rate of attainment of equilibrium affected by pressure
* Equilibrium is reached faster with higher pressure * This is because there are more particles in same volume so more collisions between reacting particles
42
How is rate of attainment of equilibrium affected by concentration
* Equilibrium is reached faster at higher concentration * This is because there are more particles in same volume so more collisions between reacting particles
43
What factors are considered when deciding conditions for industrial reaction
* Availability and cost of raw materials * Energy supplies * Optimum temperatire and pressure for high yield and fast rate of reaction * Need for catalyst
44
Why are conditions in Haber process a compromise
* High temperature increases rate of reaction however it will favour reverse reaction decreasing yield. Compromise of 450o is used to obtain sufficient rate and yield * High pressure speeds up rate of reaction and favours forward reaction increasing yield. High pressures can be dangerous and require expensive machinery so compromise of 200 atm is used
45
Why is catalyst used in Haber process
To increase rate of reaction so more product is produced within same time frame
45
What is purpuse of fertilisers
To promote plant growth
46
What chemicals might fertilisers contain
* Nitrogen * Phosphorus * Potassium compounds
47
How is salt ammonium nitrate formed | Include chemical equation
* React ammonia with nitric acid * NH3 + HNO3 --> NH4NO3
48
How can ammonium sulfate be prepared in laboratory
Titration between ammonia and sulfuric acid: * Add exact volume of 3 added to conical flask using pippette * Add few drops of indicator * Add2SO4 from burette drop by drop. Stop when indicator changes colour * Repeat adding exact volumes of reactants without indicator * Remove water by evaporation and crystallisation leaving pure crystals
49
How can ammonium sulfate be produced on industrial scale
* Raw materials obtained from Haber process (ammonia> and contact process (sulfuric acid). * Large reactor chamber is filled with ammonia gas * Sulfuric acid is sprayed into chamber from above * Ammonium sulfate crystals are produced
50
Compare laboratory method of producing ammonium sulfate with industrial process
Laboratory method: * Faster rate of reaction * Small reactant quantities can easily. be bought * Room temperature and pressure * Simple equipment required * Very small yield Industrial process * Very expensive and complex * Continuous process so continous yield * Large volumes of product * Slow rate of reaction * High energy requirement * Other industrial processes required to obtain reactants
51
What do chemical cells produce
Voltage until one of reactants is used up
52
What is used as voltage in hydrogen-oxygen fuel cell
Hydrogen and oxygen are used to produce voltage and water is only product
53
What is a fuel cell
Cell that continually produces voltage as long as it is supplied with oxygen and fuel
54
What are advantage sof using fuel cells
* No pollution produced * Produce more energy than alternative fuel like petrol * Continous process as long as fuel is supplied
55
What are disadvantages of using fuel cells
* Materials used to make them are expensive * High pressure tanks required to store oxygen and fuels like hydrogen * Hydrogen is expensive and hard to store * Efficiency is affected by temperature

Chemistry (5 decks)

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