Chemistry Paper 2 GCSE Flashcards
How do you calculate mean rate of reaction?
quantity of reactant used/ time
quantity of product formed/ time
What are the units for rate of reaction?
g/s
cm3/s
What are some factors which affect chemical reactions?
concentration of reactants in solution
pressure of reacting gases
surface area of solid reactants
What two chemicals do u use to do rates of reaction experiment?
hydrochloric acid
sodium thiosulfate solution
Which chemical do you reduce in rates of reaction experiment?
sodium thiosulfate solution
What do Catalysts do?
change the rate of chemical reactions but are not used up during the reaction
When is an equilbrium reached?
when the forward and reverse reactions occur at exactly the same rate
What happens if the concentration of one of the reactants or products is changed?
the system is no longer at equilibrium and the concentrations of all the substances will change until equilibrium is reached again
What happens if the concentration of a reactant is increased?
more products will be formed until equilibrium is reached again
What happens if the concentration of a reactant is reduced?
more reactants will react until equilibrium is reached again.
What happens If the temperature of a system at equilibrium is increased?
- the relative amount of products at equilibrium increases for an endothermic reaction
- the relative amount of products at equilibrium decreases for an exothermic reaction
What happens If the temperature of a system at equilibrium is decreased?
- the relative amount of products at equilibrium decreases for an endothermic reaction
- the relative amount of products at equilibrium increases for an exothermic reaction.
What happens for gaseous reactions at equilibrium?
- an increase in pressure causes the equilibrium position to shift towards the side with the smaller number of molecules as shown by the symbol equation for that reaction
- a decrease in pressure causes the equilibrium position to shift towards the side with the larger number of molecules as shown by the symbol equation for that reaction.
What is crude oil?
finite resource found in rocks. Crude oil is the remains of an ancient biomass consisting mainly of plankton that was buried in mud.
What is crude oil a mixture of?
very large number of compounds.
What are most of the compounds in crude oil?
hydrocarbons. Most of the hydrocarbons in crude oil are hydrocarbons called alkanes.
What are the first four members of alkanes?
methane, ethane, propane and butane.
What are many of the hydrocarbons in crude oil seperated into?
fractions, each of which contains molecules with a similar number of carbon atoms, by fractional distillation.
What does some properties of hydrocarbons depend on?
the size of their molecules, including boiling point, viscosity and flammability. These properties influence how hydrocarbons are used as fuels.
What happens during combustion of hydrocarbon fuels?
hydrocarbon fuels releases energy. During combustion, the carbon and hydrogen in the fuels are oxidised. The complete combustion of a hydrocarbon produces carbon dioxide and water.
trends in properties of hydrocarbons is limited to what?
- boiling points
- viscosity
- flammability.
What are the products of cracking?
alkanes
alkenes
What are alkenes used for?
to produce polymers and as starting materials for the production of many other chemicals.
What type of bonds does alkanes have?
single covalent bonds between carbon atoms
What happens during cracking?
a large alkane is broken down to produce smaller more useful molcules
What happens in catalytic cracking?
we use heat and a catalyst. The catalyst speeds us the reaction
What happens in steam cracking?
we use heat and steam
What are the bonds like in akenes?
have at least one double carbon to carbon covalent bond
How do we test for alkenes?
If we shake our alkene with bromine water it will go colourless
What are alkenes?
Alkene molecules are unsaturated because they contain two fewer hydrogen atoms than the alkane with the same number of carbon atoms.
What are the first four members of the homologous series of alkene?
ethene, propene, butene and pentene
How does alkenes react with oxygen?
Alkenes react with oxygen in combustion reactions in the same way as other hydrocarbons, but they tend to burn in air with smoky flames because of incomplete combustion.
What do alkenes react with?
Alkenes react with hydrogen, water and the halogens, by the addition of atoms across the carbon-carbon double bond so that the double bond becomes a single carbon-carbon bond.
What does alcohols contain?
Alcohols contain the functional group –OH
How are Aqueous solutions of ethanol produced?
sugar solutions are fermented using yeast.
What functional group for carboxylic acids have?
Carboxylic acids have the functional group –COOH
When is a strong acid completely ionised?
in aqueous solution
When is A weak acid is only partially ionised?
in aqueous solution
For a given concentration of aqueous solutions what is the strength of an acid like compared to the pH?
the stronger an acid, the lower the pH.
As the pH decreases by one unit, what happens to the hydrogen ion concentration of the solution?
increases by a factor of 10
What is a pure substance in chemistry?
a pure substance is a single element or compound, not mixed with any other substance
What are pure elements and compounds like?
Pure elements and compounds melt and boil at specific temperatures. Melting point and boiling point data can be used to distinguish pure substances from mixtures
What is a formulation?
A formulation is a mixture that has been designed as a useful product. Many products are complex mixtures in which each chemical has a particular purpose. Formulations are made by mixing the components in carefully measured quantities to ensure that the product has the required properties. Formulations include fuels, cleaning agents, paints, medicines, alloys, fertilisers and foods.
What can chromatography be used for?
Chromatography can be used to separate mixtures and can give information to help identify substances
How do you work out the Rf value during chromatography?
distance moved by substance/ distance moved by solvent
What will happen to some compounds in a mixture and pure substances during chromatography?
The compounds in a mixture may separate into different spots depending on the solvent but a pure compound will produce a single spot in all solvents
How do we test for hydrogen?
uses a burning splint held at the open end of a test tube of the gas. Hydrogen burns rapidly with a pop sound.
How do we test for oxygen?
uses a glowing splint inserted into a test tube of the gas. The splint relights in oxygen
How do we test for carbon dioxide?
uses an aqueous solution of calcium hydroxide (lime water). When carbon dioxide is shaken with or bubbled through limewater the limewater turns milky (cloudy).
How do we test for chlorine?
The test for chlorine uses litmus paper. When damp litmus paper is put into chlorine gas the litmus paper is bleached and turns white.
How much of the atmosphere is nitrogen?
about four-fifths (approximately 80 %)
How much of the atmosphere is oxygen?
about one-fifth (approximately 20 %)
How did oxygen increase?
Algae and plants produced the oxygen that is now in the atmosphere by photosynthesis. Algae first produced oxygen about 2.7 billion years ago and soon after this oxygen appeared in the atmosphere. Over the next billion years plants evolved and the percentage of oxygen gradually increased to a level that enabled animals to evolve.
How did Carbon dioxide decrease?
Algae and plants decreased the percentage of carbon dioxide in the atmosphere by photosynthesis. Carbon dioxide was also decreased by the formation of sedimentary rocks and fossil fuels that contain carbon.
Greenhouse gases
Greenhouse gases in the atmosphere maintain temperatures on Earth high enough to support life. Water vapour, carbon dioxide and methane are greenhouse gases.
Some human activities increase the amounts of greenhouse gases in the atmosphere. What do these include?
• carbon dioxide • methane.
An increase in average global temperature is a major cause of what?
climate change
What is the carbon footprint?
The carbon footprint is the total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event.
How can the carbon footprint be reduced?
The carbon footprint can be reduced by reducing emissions of carbon dioxide and methane
What is a major source of atmospheric pollutants?
combustion of fuels
What is carbon monoxide?
Carbon monoxide is a toxic gas. It is colourless and odourless and so is not easily detected
What does Sulfur dioxide and oxides of nitrogen cause?
respiratory problems in humans and cause acid rain.
What does Particulates cause?
global dimming and health problems for humans.
Why does humans use the earths resources?
to provide warmth, shelter, food and transport.
What are some finite resources?
oil, natural gas and coal
What are some natural resources?
wood, wind
For humans drinking water should have sufficiently low levels of what?
dissolved salts and microbes
What is potable water?
Water that is safe to drink is called potable water. Potable water is not pure water in the chemical sense because it contains dissolved substances.
What is most potable water produced by?
- choosing an appropriate source of fresh water
- passing the water through filter beds
- sterilising
What is the pH of pure water?
7
How do we test for dissolved solids in water?
weigh water place in evaporating basin heat if there was some in there the mass would increase
What is phytomining?
Phytomining uses plants to absorb metal compounds. The plants are harvested and then burned to produce ash that contains metal compounds.
What is bioleaching?
Bioleaching uses bacteria to produce leachate solutions that contain metal compounds.
What does some sewage treatments include?
- screening and grit removal
- sedimentation to produce sewage sludge and effluent
- anaerobic digestion of sewage sludge
- aerobic biological treatment of effluent.
What are life cycle assessments?
Life cycle assessments (LCAs) are carried out to assess the environmental impact of products in each of these stages: • extracting and processing raw materials • manufacturing and packaging • use and operation during its lifetime • disposal at the end of its useful life, including transport and distribution at each stage
