Unit 3 Flashcards
(123 cards)
1
Q
What are the main objectives of industrial processes?
A
The main objectives are to maximise profit and minimise the impact on the environment.
2
Q
List three factors that influence industrial process design.
A
- Availability, sustainability, and cost of feedstock.
- Opportunities for recycling
- Energy requirements
3
Q
How does the availability and sustainability of feedstock affect industrial processes design?
A
Readily available and sustainable feedstocks reduce costs and environmental impact, ensuring long-term viability.
4
Q
Why is it important to consider opportunities for recycling in industrial processes?
A
Recycling reduces waste, conserves resources and improves the overall efficiency of the process.
5
Q
How does product yield influence the design of an industrial process?
A
Higher product yield increases profitability and reduced waste, making the process more efficient.
6
Q
What are some environmental considerations in industrial processes design?
A
- Minimising waste.
- Avoiding the use of production of toxic substances.
- Designing products that will biodegrade if appropriate.
7
Q
Why is it important to minimise waste in industrial processes?
A
Minimising waste reduces environmental impact and enhances process efficiency.
8
Q
How can designing biodegradable products benefit the environment?
A
Biodegradable products break down naturally, reducing pollution and waste accumulation.
9
Q
Why are chemical equations balanced using formulae and state symbols?
A
To ensure the law of conservation of mass is obeyed and to indicate the physical states of the substances involved.
10
Q
What information can be determined from the mole ratios in a balanced equation?
A
The relative amounts of reactants and products involved in the reaction.
11
Q
How is the gram formula mass (GFM) of a substance calculated?
A
By summing the relative atomic masses of all atoms in the formula.
12
Q
What is the relationship between the mass and the number of moles
A
Number of moles = mass + GFM
13
Q
How can the number of moles of a solute be calculated from a given mass?
A
By dividing the mass of the solute by its GFM
14
Q
What is the molar volume of a gas?
A
The volume occupied by one mole of any gas at a certain temperature and pressure.
15
Q
Why is the molar volume the same for all gases at a certain temperature and pressure?
A
Because gases occupy the same volume per mole under the same conditions.
16
Q
How can the volume of a gas be calculated from its molar volume and number of males.
A
Volume of gas = number of moles x molar volume
17
Q
What four pieces of information are required to calculate the concentration of a solution?
A
- Mass of solute.
- Number of moles of solute.
- Volume of solution.
- Concentration of the solution.
18
Q
How can the volume of a solution be calculated given the number of moles and the concentration?
A
Volume = number of moles + concentration
19
Q
What is the formula to calculate the concentration of a solution in moll-1?
A
Concentration = number of moles + volume(in litres).
19
Q
How can the mass of a solute in a solution be determined from the concentration and volume?
A
Mass = number of moles x GFM
19
Q
What is percentage yield and how is it used to measure reaction efficiency?
A
Percentage yield measures the degree to which the limiting reactant is converted into the desired product.
20
Q
How is the percentage yield calculated?
A
% yield = (actual yield/ theoretical yield) x 100.
21
Q
What is the difference between theoretical yield and actual yield?
A
Theoretical yield is the maximum amount of product possible, while actual yield is the amount obtained under real conditions.
22
Q
Why is the limiting reactant important in determining the theoretical yield?
A
It controls the maximum amount of product that can be formed?
23
Why is an excess of a less expensive reactant often used in industrial processes?
To ensure the costly reactant is fully converted into the desired product.
24
What does the percentage yield tell us about the conversion of the limiting reagent?
It indicates how much of the limiting reagent was converted into the desired product.
25
What is atom economy and how is it different from percentage yield?
Atom economy measures how much of the reactants' mass is converted into the desired product, while percentage yield measures how much of the limiting reactant is converted into the product.
26
28. How is the percentage atom economy calculated?
% Atom economy = (Mass of desired product ÷ Total mass of reactants) x 100.
27
29. Why might a reaction with a high percentage yield still have a low atom economy?
If large amounts of by-products are formed, the atom economy can be low despite a high yield.
28
Why is high atom economy desirable in industrial processes?
It reduces waste and makes the process more sustainable and cost-effective.
28
How can percentage yield be used to calculate the cost of reactants required to produce a certain mass of product?
By considering the percentage yield, the amount of reactant required can be adjusted to account for the expected efficiency.
29
Why is it important to minimise the cost of reactants in an industrial process?
To maximise profitability and improve overall process efficiency.
30
How does atom economy impact the overall cost and efficiency of a process?
Higher atom economy reduces waste and by-products, lowering production costs.
31
What is the relationship between the percentage yield and the cost-effectiveness of a reaction?
Higher percentage yield reduces the amount of wasted reactants, improving cost efficiency.
32
How can the limiting reactant be identified from a balanced equation?
By comparing the mole ratio of reactants to the amount present in the reaction.
33
Why is identifying the reactant in excess important in industrial processes?
To ensure that the costly reactant is fully consumed, maximising yield.
34
What role does the limiting reactant play in determining the maximum yield of a reaction?
It determines the maximum amount of product that can be formed.
35
How can industrial processes be designed to reduce environmental impact?
By minimising waste, reducing energy use, and avoiding toxic substances.
36
What role does recycling play in improving the sustainability of an industrial process?
Recycling reduces waste and conserves resources, improving sustainability.
37
Why should toxic substances be avoided or minimised in industrial processes?
To prevent environmental damage and protect human health.
38
How does the marketability of byproducts influence the success of an industrial process?
If by-products can be sold or used, they reduce waste and improve profitability.
39
Why is it important to consider product yield when designing an industrial process?
Higher yield reduces costs, waste, and environmental impact.
40
Why must reaction rates be controlled in industrial processes?
Reaction rates must be controlled to ensure the process is economically viable and safe.
40
What could happen if a reaction rate is too low in industry?
If the reaction rate is too low, the process becomes uneconomical.
40
What risk is associated with a reaction rate that is too high?
If the reaction rate is too high, the a risk of explosion.
41
What is the relationship between reaction time and relative rate?
Relative rate is calculated as 1/ time. shorter the time, the faster the rate.
41
What theory is used to explain how different factors affect reaction rates?
Collision theory explains how different factors influence reaction rates.
41
According to collision theory, what must happen for a chemical reaction to occur?
For a reaction to occur, particles must collide with sufficient energy and correct orientation.
41
How does increasing the concentration of reactants affect reaction rate?
Increasing concentration increases the number of particles in a given volume, increasing collision frequency and reaction rate.
42
How does increasing the pressure of a gas affect reaction rate?
Increasing pressure in gas reactions increases particle collisions, increasing the rate.
43
What effect does increasing the surface area (by reducing particle size) have on reaction rate?
Increasing surface area exposes more particles for collisions, thus increasing the rate.
44
How does temperature influence the rate of a reaction?
Increasing temperature increases particle energy and collision frequency, speeding up the reaction rate.
45
What is collision geometry and how does it affect reaction success?
Collision geometry refers to the orientation of particles when they collide - only correct alignments lead to a successful reaction.
46
What is a potential energy diagram used for in chemistry?
A potential energy diagram shows the energy pathway of a chemical reaction.
47
What does the enthalpy change represent in a reaction?
Enthalpy change is the energy difference between reactants and products.
48
What sign does enthalpy change have for exothermic reactions?
For exothermic reactions, the enthalpy change is negative (products have less energy than reactants).
49
What sign does enthalpy change have for endothermic reactions?
For endothermic reactions, the enthalpy change is positive (products have more energy than reactants).
50
What is activation energy?
Activation energy is the minimum energy required for a reaction to occur.
51
What is the activated complex?
The activated complex is a high-energy, unstable arrangement of atoms at the top of the energy barrier.
51
Where on the energy diagram is the activated complex found?
The activated complex is found at the peak of the curve in the diagram.
51
How does a catalyst affect the activation energy of a reaction?
A catalyst provides an alternative pathway with a lower activation energy.
52
How is the effect of a catalyst shown on a potential energy diagram?
On a potential energy diagram, a catalyst is shown by a lower activation energy curve compared to the uncatalysed reaction.
52
What does temperature measure in terms of particles?
Temperature is a measure of the average kinetic energy of particles.
53
What is the minimum kinetic energy required for a reaction to occur?
The activation energy is the minimum kinetic energy needed for particles to react.
53
What does an energy distribution diagram show?
An energy distribution diagram shows the range of kinetic energies of particles in a sample.
54
How does increasing temperature affect the distribution of kinetic energy among particles?
When temperature increases, more particles have kinetic energy above the activation energy threshold.
55
Why does a higher temperature increase the reaction rate?
Higher temperature means more successful collisions, which increases the reaction rate.
56
How does the addition of a catalyst affect the number of particles able to react?
A catalyst increases the number of particles that can react by lowering the activation energy.
57
What happens to the activation energy barrier when a catalyst is used?
The activation energy barrier is lowered when a catalyst is used.
58
How can both temperature and catalysts be explained using energy distribution diagrams?
Energy distribution diagrams shows how increasing temperature or adding a catalyst increases the area under the curve beyond the activation energy, leading to more frequent successful collisions.
59
What is enthalpy a measure of?
The chemical energy in a substance.
60
What term describes a reaction that releases heat energy?
Exothermic.
61
Why might exothermic reactions require cooling in industry?
To prevent the temperature from rising excessively.
62
What term describes a reaction that absorbs heat energy?
Endothermic.
63
Why are endothermic reactions potentially costly in industrial settings?
They require the supply of heat energy to maintain the reaction rate.
64
Which equation is used to calculate the quantity of heat energy released in a reaction?
En = стДт.
65
In the equation En = cmAT, what
does each symbol represent?
- En = energy released (in joules, J)
- c = specific heat capacity (in J g-' °C-)
- m = mass (in grams, g)
- AT = change in temperature (in °C)
66
What units should be used for mass, specific heat capacity, and temperature change when using the
equation En = cmAT?
- Mass = grams (g)
- Specific heat capacity = J g-' °C-'
- Temperature change = °C
67
How can the enthalpy change for a reaction be determined experimentally?
By measuring the heat energy released or
absorbed using En = cmAT.
68
What is the definition of the enthalpy of combustion of a substance?
The enthalpy change when one mole of a substance burns completely in oxygen.
69
What does Hess's Law state about the enthalpy change for a reaction?
That it is independent of the route taken.
70
How can Hess's Law be used to calculate enthalpy changes?
By combining known enthalpy changes of steps in a reaction pathway to find the overall change.
71
Why is Hess's Law useful for reactions that are difficult to study directly?
Because it allows indirect calculation of enthalpy changes.
72
What is meant by the molar bond enthalpy?
The energy required to break one mole of bonds in a diatomic molecule.
73
What is a mean molar bond enthalpy, and why is it used?
An average value of bond energies for a bond occurring in different compounds-used because bond energies vary slightly depending on the molecular environment.
74
How can bond enthalpies be used to estimate the enthalpy change of a gas-phase reaction?
By subtracting the energy released when bonds form (in products) from the energy required to break bonds (in reactants).
75
What must be considered when using bond enthalpies to calculate the enthalpy change of a reaction?
Only works for reactions where all reactants and products are in the gas phase.
76
What happens to energy when chemical bonds are broken and formed?
- Breaking bonds requires energy (endothermic).
- Forming bonds releases energy (exothermic).
77
What is meant by a reversible reaction?
A reversible reaction is one in which the products can react to reform the reactants.
78
What is a closed system in the context of chemical reactions?
A closed system is one where no substances can enter or leave, allowing equilibrium to be established.
79
What happens to the rates of the forward and reverse reactions when a system reaches dynamic equilibrium?
At dynamic equilibrium, the rate of the forward reaction equals the rate of the reverse reaction.
80
At equilibrium, do the concentrations of reactants and products continue to change?
No, the concentrations of reactants and products remain constant at equilibrium, although both reactions are still occurring.
81
Are the concentrations of reactants and products always equal at equilibrium?
No, they are constant but not necessarily equal.
82
What does it mean when a reaction is said to be in a state of dynamic equilibrium?
It means the forward and reverse reactions are occurring at the same rate, and the concentrations of reactants and products remain constant over time.
83
Why might chemists want to shift the position of equilibrium in an industrial process?
To increase the yield of the desired product and maximise profits.
83
What effect does increasing the temperature have on the position of equilibrium in an exothermic reaction?
Increasing the temperature shifts the equilibrium position to the left (toward the reactants).
84
How does increasing temperature affect the equilibrium position of an endothermic reaction?
It shifts the equilibrium to the right (toward the products).
85
What effect does increasing pressure have on a reaction involving gases?
It shifts the equilibrium toward the side with fewer gas molecules.
86
How can removing products affect the position of equilibrium?
It shifts the equilibrium to the right, favouring the formation of more products.
87
What happens if you add more reactants to a system at equilibrium?
The equilibrium shifts to the right to produce more products.
88
How can changing concentration shift the equilibrium position?
Adding or removing reactants/products will shift the equilibrium to oppose the change and restore balance.
89
What effect does a catalyst have or the rate of a reversible reaction?
A catalyst increases the rate of both the forward and reverse reactions equally.
90
Does a catalyst change the position of equilibrium?
No, it does not change the position of equilibrium.
91
How does a catalyst help in reaching equilibrium faster?
It lowers the activation energy, so both reactions occur more quickly, allowing equilibrium to be reached faster.
92
Why is a catalyst used if it doesn't change the position of equilibrium?
It helps speed up the reaction and reduce the time required to reach equilibrium, which is Important in industrial processes.
93
What is the purpose of chromatography?
To separate the components present within a mixture.
93
What types of differences between substances does chromatography use to separate them?
Differences in their polarity or molecular size.
94
How can the identity of a component in chromatography be determined?
By the distance it has travelled or by its retention time, depending on the method used.
95
What does retention time refer in chromatography?
The time it takes for a substance to travel through the apparatus.
96
How can the results of chromatography be visually presented?
As a graph with quantity on the y-axis and retention time on the x-axis.
97
On a chromatographic graph, what does the y-axis typically represent?
An indication of the quantity of the substance present.
98
What does the X-axis represent on a chromatographic graph?
The retention time.
99
Can chromatography be used to estimate the quantity of a substance present? How?
Yes, by analysing the height or area under the peak on a chromatographic graph.
100
What is volumetric analysis used for in chemistry?
To determine the concentration of an unknown substance using a solution of known concentration.
101
What is titration?
A technique to determine the volumes of solution required to reach the end-point of a chemical reaction.
102
What is meant by the 'end-point' of a titration?
The point at which the reaction is complete, often indicated by a colour change.
103
What is an indicator used for in titration?
To show when the end-point of the reaction has been reached.
104
What are standard solutions?
Solutions of accurately known concentration.
105
What titre volumes are considered concordant?
Volumes within 0.2 cm3 of each other.
106
Why is an indicator not needed in redox titrations using acidified permanganate?
Because purple permanganate solution turns colourless when it is reduced.
107
What happens to the colour of acidified permanganate during a redox titration when it is reduced?
It turns from purple to colourless.
108
What information is required to calculate the concentration of a solution using titration data?
The balanced equation, concentrations, and volumes of the solutions.
109
How can the volume of an unknown solution be calculated in a titration?
Using the known volume and concentration of the other solution and the balanced chemical equation.
