E Chemistry Lent and Summer
Terms in this set (63)
Which two substances are heated together to produce ammonia in the laboratory?
Calcium hydroxide and ammonium chloride.
What are the important properties of ammonia?
Colourless, pungent gas.
Less dense than air.
How can we test for ammonia in the laboratory?
The gas turns damp red litmus paper blue.
What is the equation for the reversible reaction which occurs in the "Ammonia Smokescreen" experiment?
NH3 + HCL = NH4CL
Which two elements must be reacted together to make ammonia industrially
Nitrogen and hydrogen.
From what raw materials are nitrogen and hydrogen elements normally obtained?
Nitrogen comes from the air.
Hydrogen is produced by chemical reactions from natural gas
What is the equation for the exothermic reaction which produces ammonia?
N2 (g) + 3H2 (g) = 2NH3 (g)
When is a reversible reaction said to have reached dynamic equilibrium?
When it is going both ways at the same rate.
At what pressure is the Haber Process normally done?
About 200 atmospheres.
What are the advantages of doing the Haber process under high pressure?
The reaction is faster.
The yield of ammonia is higher.
What is the disadvantage of using too high a pressure?
Very high pressures are too expensive.
What problem occurs if the temperature is too low in the Haber process
The reaction is too slow.
What problem occurs if the temperature is too high in the Haber process
This encourages the reverse reaction and reduce the yield.
What is used as a catalyst in Haber process
How is the ammonia separated from unreacted nitrogen and hydrogen?
The mixture is cooled, and the ammonia condenses to a liquid.
What is done with the unreacted nitrogen and hydrogen during the Haber process
They are piped back into the reactor
How is ammonia converted to nitrogen oxide?
It reacts with oxygen in the air, at high temperature and with a platinum catalyst.
How is nitric acid then produced from Nitrogen oxide
Nitrogen oxide reacts with water.
How are fertilisers made from ammonia
By neutralising it with an acid (nitric, sulfuric or phosphoric).
How do fertilisers help improve the growth of plants?
By providing nitrogen compounds which plants can use.
What is the formula of the ammonium ion?
How is the NH4+ ion formed from ammonia?
By adding any acid.
What happens when a compound containing ammonium ions is warmed with aqueous alkali?
Ammonia gas is formed.
What is the equation for when a compound containing ammonium ions is warmed with aqueous alkali?
NH4+ + OH- = NH3 + H20.
Hydrochloric acid forms
Sulfuric acid produces
Nitric acid produces
Acid + Base = Salt + Water
HCL + NaOH = NaCL + H2O
Acid + Metal = Salt + Hydrogen
H2SO4 + Mg = MgSO4 + H2
Acid + Carbonate = Salt + Water + Carbon dioxide
2HCL + CaCO3 = CaCL2 + H2O + CO2
Litmus colour at low/high ph
Phenolphtatein colour at low/high ph
Methyl orange colour and low/high
How is it possible for "Universal Indicator" to show so many different colours?
It is a mixture of several indicators.
Which ion is always produced when an acid dissolves in water?
Which ion is always produced when an alkali dissolves in water?
Examples of alkalis include:
Sodium hydroxide, and ammonia.
Which reaction between ions always occurs when aqueous solutions of an acid and an alkali are mixed?
H+ + OH- = H2O
How were fossil fuels formed?
Anaerobic decay, over geological timescales, of plant and animal remains, covered by layers of sedimentary.
What is meant by a hydrocarbon?
A compound of
carbon and hydrogen only.
How does fractional distillation work?
Hot crude oil enters near the bottom of a fractioning column.
Temperature decreases up the column.
By evaporation and condensation up the column, the oil is separated into 'fractions' with different boiling ranges, which are tapped off at different heights.
Complete combustion of a hydrocarbon gives two products:
Carbon dioxide and water.
There are simple chemical tests for H2O and CO2
Water turns white (anhydrous) copper sulfate to blue. Lime water goes milky
In what conditions may incomplete combustion occur?
lack of oxygen
What other gases may be produced by burning fossil fuels?
Sulphur dioxide, if the fuel contains sulphur.
Nitrogen oxides, when high temperatures cause nitrogen and oxygen in the air to combine.
Way to remember the first 4 alkanes
My Elephants Prefer Bananas: Methane, Ethane, Propane, Butane
What is meant by a homologous series?
Each has one more "CH2" unit than the one before.
They have similar chemical properties.
They have the same general formula.
They show a trend in physical properties. Physical properties are things that don't involve a chemical reaction, such as boiling and melting points
The general formula of the alkanes is:
Cn + H2n + 2
What is the shape of a methane molecule?
What happens to the boiling points of the alkanes as the molecules get larger? Why?
The boiling points of the alkanes increase, because the forces between molecules get stronger.
Molecules with the same molecular formula but different arrangements of atoms are called:
Larger alkanes are used to make:
Liquid fuels such as petrol.
Do the alkanes have any other reactions, apart from combustion?
A substitution reaction with chlorine and bromine.
What conditions are needed in a substitution reaction?
Ultraviolet light to start the reaction.
The alkenes are another homologous series of hydrocarbons. They are different from the alkanes because:
Each alkene molecule contains a double bond.
They are therefore said to be unsaturated.
What is the shape of an ethene molecule?
It is planar.
Each carbon forms a triangle of bonds.
In an alkene there is a double bond in the molecule.
The general formula of the alkenes is
how to test for alkanes and alkenes
Alkenes will turn "bromine water" from orange/brown to colourless.
Alkanes will not react with bromine in these conditions.
What does cracking involve?
The alkanes are broken down to smaller molecules by heating to about 600ºC-700ºC
It is broken down into smaller alkanes and alkenes.
A catalyst is also present (aluminium oxide).
Ethanol production by fermentation
sugars = ethanol + CO2
dissolved in water
absence of air
Low temperature (30C).
Catalyst zymase (from yeast)
The reaction of ethene with steam is:
A better way to obtain a purer product.
A continuous process. (Where we keep on pumping the material in and collecting the product at the other end)
Fermentation has the advantage that:
It uses renewable resources (sugar cane), rather than using ethane produced from fossil fuels.
What issues arise from incomplete combustion
Carbon monoxide may be formed.
This is a colourless, odourless, toxic gas.
It binds to haemoglobin in place of oxygen.