The Chemical Industry

What is the percentage of nitrogen in the Earth's atmosphere?

78%

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Describe the reagents and conditions required for the Haber Process

Requires nitrogen and hydrogen, 450 degrees Celsius with 200 atm pressure and an iron catalyst

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What type of bonding takes place in a nitrogen molecule?

Covalent bond (triple bond)

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What type of bonding takes place in an ammonium ion (between the nitrogen atom and hydrogen atom)?

Dative covalent bonding (both bonding pair of electrons come from the same atom, in this case nitrogen)

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How can you convert ammonia into ammonium ions?

Add hydrogen ions

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Why can't nitrogen be used directly by plants to make proteins?

Nitrogen is very unreactive. Also, almost all the nitrogen in the soil is present in complex organic compounds so it is not readily available to plants

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Describe the appearance of nitrogen oxide

A colourless gas which turns brown (NO2) in air

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Where does nitrogen oxide come from?

Combustion processes (vehicle engines), thunderstorms and formed in the soil by denitrifying bacteria

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Describe the appearance of nitrogen dioxide

A brown gas

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Where does nitrogen dioxide come from?

From the oxidation of NO in the atmosphere

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Describe the appearance of dinitrogen oxide

A colourless gas

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Where does dinitrogen oxide come from?

Formed in the soil by denitrifying bacteria

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What are the type kinds of nitrate ions involved in the nitrogen cycle?

Nitrate (III) and nitrate (V)

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What is the test for nitrate (V) ions?

Heat the sample with sodium hydroxide solution and Devarda's alloy (Cu/Al/Zn)

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What is the positive test for nitrate (V) ions?

Damp red litmus paper turns blue (indicates that ammonia has been produced)

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What is the test for ammonium ions?

Heat the sample with sodium hydroxide solution

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What is the positive test for ammonium ions?

Damp red litmus paper turns blue (indicates that ammonia has been produced)

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What are the two stages for nitric acid production?

Oxidation of ammonia and absorption of the resulting nitrogen oxides

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How does increasing the pressure of a reaction affect the position of equilibrium?

Increasing the pressure moves the equilibrium to the side of the equation with fewer gas molecules (reducing the pressure)

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How does temperature affect the equilibrium constant?

As the temperature increases, the equilibrium constant increases

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How does a catalyst affect the equilibrium constant?

A catalyst does not affect the equilibrium constant (or the position of equilibrium)

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Which factors may change the composition of the mixture?

Concentration and total pressure

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Which factor changes the composition of mixture?

Temperature

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Which factor does not change the composition of mixture?

Catalysts

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What does the term 'rate of reaction' mean?

The rate at which reactants are converted into products

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What is a reaction mechanism?

A way of demonstrating how rate of reaction changes and the way reactions occur

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List the five ways of measuring the rate of reaction

Measuring volumes of gases evolved, measuring mass changes, pH measurement, colorimetry and chemical analysis (including titration)

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What is chemical analysis?

Taking samples of the reaction mixture at regular intervals and stopping the reaction in the sample before analysis by a process known as quenching

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Which reagents can be used to quench a sample?

Sodium hydrogencarbonate (to neutralised the acidic catalyst produced) or deionised water

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Which method can be used to measure the rate of reaction for the decomposition of hydrogen peroxide?

Measure the volume of gas evolved (volume of oxygen produced is measure in the inverted measuring cylinder or burette)

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What does the term 'initial rate' mean?

The rate of reaction at the start

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How do you calculate the initial rate?

Draw a tangent to the curve (on the graph) at the point t=0 and measure the gradient of the tangent

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How is the rate equation for any chemical reaction determined?

By using experiments to find the order of reaction with respect to the reactants (you cannot predict the rate equation for a reaction from its balanced equation)

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How do you work out the overall order of a reaction?

The sum of the power to which the concentrations need to be raised

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What are the units of the rate constant for zero order?

mol dm-3s-1

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What are the units of the rate constant for first order?

s-1

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What are the units of the rate constant for second order?

dm3 mol-1s-1

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What happens to the rate constant as the temperature increases?

The rate constant increases

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Which equation can be used to calculate the impact of changes of temperature and activation energy on the rate constant?

The Arrhenius Equation

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What happens to the reaction rate when there is a temperature rise of 10 degrees Celsius?

Reaction rates are roughly doubled

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What is a catalyst?

A catalyst provides can alternative route with a lower activation energy (Ea falls from 50kJ mol-1 to 40kJ mol-1 in a reaction taking place at 50 degrees Celsius)

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What is the progress curve method?

A graph involving a progress curve showing how the concentration of a reactant (or product) changes as the reaction proceeds

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What is the initial rate method?

Involves drawing tangents at the origin of different progress curves. The initial rates for different concentrations can be used to find the order

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Describe a concentration-time graph for zero order

Straight line with a negative correlation

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Describe a concentration-time graph for first order

Inversely proportional (curve moving downwards)

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Describe a concentration-time graph for second order

Inversely proportional (curve moving downwards)

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Describe a rate-concentration graph for zero order

Straight horizontal line

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Describe a rate-concentration graph for first order

Directly proportional

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Describe a rate-concentration graph for second order

Exponential graph (curve moving upwards). [X]^2 leads to a directly proportional graph

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Describe an alternative way of measuring initial rate of reaction

Measure how long the reaction takes to produce a small, fixed amount of one of the products (reaction time). High rate leads to small reaction time and low rate leads to large reaction time

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Give an example of an experiment where the reaction time can be measured (to find initial rate of reaction)

Reaction between sodium thiosulfate solution and hydrochloric acid

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If a graph of 1/t is plotted against the concentration of the thiosulfate solutions used, what will be the shape of the graph?

Straight line (proportional)

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What does the term 'half-life' mean?

The time taken for the concentration of a reactant to decrease by half

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What does a constant half life indicate about the order of reaction?

The order of reaction is first order with respect to the reactant (zero order or second order if the half lives are not constant)

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What is the rate determining step?

The slowest step in a mechanism

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Describe how the rate equation can be used to find information about the rate-determining step and the reaction mechanism

If the reactants are not in the rate equation, then they are not in the slow step (but in fast steps). Reactants in the rate equation will be in the slow step. Order of reaction for each substance will tell you the number of moles

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What does the rate of reaction depend on for all reactions?

The size of the activation enthalpy (large Ea - slow reaction, small Ea - fast reaction)

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For a reversible reaction, what will happen when the temperature is increased?

The reaction will favour the endothermic reaction (but would increase rate of reaction)

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For a reversible reaction, what will happen when the temperature is decreased?

The reaction will favour the exothermic reaction (but would decrease rate of reaction)

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What are feedstocks?

Reactants that go into a chemical process

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In what form are reactants easy to handle?

In the form of gases and liquids (transported in pipes). Solids are expensive to handle

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How are transportation costs for solids reduced?

By melting solids and maintain them as hot liquids (e.g. sulfur). Also, solids are mixed with a liquid to form slurry

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What are the feedstocks for ammonia?

Methane, air and water

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What are the feedstocks for nitric acid?

Ammonia, air and water

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What are the feedstocks for sulfuric acid?

Sulfur, air and water

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What are the feedstocks for ethanoic acid?

Methanol, carbon monoxide and water

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What are the raw materials for ammonia, nitric acid, sulfuric acid and ethanoic acid?

Natural gas/oil, air, water, coal

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Name some of the fractions produced from the distillation of crude oil

Liquefied petroleum gas, naphtha, gas (diesel) and oil

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Name the compounds the fractions from distillation of crude oil are converted to

Alkenes, branched-chain alkanes, cycloalkanes and aromatic hydrocarbons

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What is a co-product?

A chemical produced along with the main product

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What is a by-product?

A secondary product derived from the reaction (unwanted)

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What are fixed (indirect) costs?

Those incurred by the company (e.g. labour costs, land purchase or rental, sales expenses etc.)

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How is the fixed cost element in the production cost calculated?

Spreading the total annual charges over the number of units of the product produced per year

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What are variable (direct) costs?

Costs relating specifically to the unit of production (e.g. raw materials, effluent treatment and disposal, cost of distributing product)

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What would happen if no production occurs?

Variable costs will not be incurred whereas fixed costs will still have to be paid

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What are the issues with the use of high temperature and pressure?

Requires a very specialised, expensive chemical plant that is costly to maintain (and difficult to control chemical reactions)

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Describe some of the ideas in green chemistry

Reduce use of feedstocks to a minimum, recycle unused reactants and solvents, reduce energy consumption to a minimum (results in minimum waste)

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What are the ways of reducing cost in production?

Using a catalysts, recycle unreacted feedstock, save energy (that would be lost to the environment), sell on a co-product

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How can be efficiency of production be increased?

Thermal energy can be conserved by lagging pipes and using heat exchangers. Energy from exothermic parts can be used to supply energy to endothermic parts or used to raise temperature of reactants. Also steam is regenerated

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What does the Health and Safety at Work Act, 1974 state?

UK legislation places responsibility for health/safety with employer. Personal safety is rated very highly (e.g. eye-baths, showers, toxic gas refuges, breathing apparatus, emergency control rooms, medical centre)

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What does the Control of Substances Hazardous to Health Regulations, 2002 state?

Control the amount of exposure that employees have to chemicals that can cause a hazard (minimise exposure, alter temperature to reduce amount of toxic by-product produced)

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What is a hazard?

The potential that a hazardous substance has to cause harm

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What is a risk?

The likelihood the hazardous substance will cause harm under the conditions of its use

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What does the Control of Major Accident Hazards Regulations, 1999 state?

Company works with the local authority and emergency services when using certain reagents (e.g. chlorine)

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What does the Registration, Evaluation, Authorisation, and Restriction of Chemicals, 2007 state?

Puts responsibility on the company and required that many manufactured or imported chemical substances must be registered with the European Chemicals Agency (must be classified e.g. substances of very high concern - cause cancers/genetic mutations)

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The Chemical Industry

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