chem chem chem

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  • Created by: xxemilyxx
  • Created on: 13-06-14 15:56
Why and how does dry cleaning work?
Both the solvent and grease molecules have weak intermolecular forces, so when the solvent is applied, intermolecular forces form between solvent and grease molecules. The grease gets surrounded by solvent molecules so when the solvent is removed so
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What do biological detergents do?
they contain enzymes that help break down insoluble molecules into smaller soluble ones so you can wash clothes at lower temperatures.
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Monounsaturated fats ...
only contain one double bond C=C in their carbon chains
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Polyunsaturated fats..
contain more than one double bond C=C
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What happens when you put unsaturated oil or fat in bromine?
An addition reaction takes place and a colourless compound is formed.
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What oils are liquid at room temperature?
Unsaturated vegetable oils, They can be hardened by reacting them with hydrogen and a nickel catalyst at 60C. The hydrogen reacts with the double bonded carbons -hydrogenation
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What alcohol is reacted with fatty acids to make fats and oils?
Glycerol
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What is an emulsion?
Shaking oil and water together vigorously, breaking up the oil into small droplets which disperse through the water.
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Equation to make soap (saponification)
Fat + sodium hydroxide -> soap + glycerol The hot sodium hydroxide splits up the fats and oils
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formula for alcohols
C(n)H(2n+1)OH
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How is ethanol made?
Fermentation: glucose->ethanol+CO(2) OR Hydrating ethene ethene+water(steam)->ethanol
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What is water hardness caused by?
Carbon dioxide + water + calcium carbonate-> calcium hydrogencarbonate Calcium and magnesium ions. Magnesium sulfate dissolves in water. Calcium carbonate reacts with acids (rain water) to become calcium hydrogencarbonate which is soluble.
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What is temporary hardness caused by?
HCO(3)- the hydrogencarbonate ion
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How is temporary hardness removed?
Boiling it decomposes the hydrogencarbonate into CaCO(3) Calcium hydrogencarbonate -> calcium carbonate + water + carbon dioxide
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How does washing soda remove both types of hardness?
The carbonate ions in sodium carbonate join to the calcium ions to make insoluble calcium carbonate. Ca^2+ (aq) + CO(3)^2- (aq) -> CACO(3) (s)
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Ion exchange resin
lots of sodium or hydrogen ions are exchanged with calcium and magnesium ions.
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What is a free radical?
When a covalent bond is broken evenly so each atom gets one of the shared electrons making them very reactive
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What damages the Ozone layer?
Chlorine free radicals from CFCs made from carbon-chlorine by UV light
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How does it damage the ozone layer?
it reacts with the ozone O(3) turning it into oxygen and chlorine oxide which reacts with ozone to make 2 oxygen molecules and another Cl- radical this repeats the cycle.
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What are alternatives to CFCs?
Alkanes. Hydrofluorocarbons (HFCs)
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What happens in a fuel cell?
Hydrogen and oxygen react to make water. This reaction gives out energy
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What goes into the anode compartment?
Hydrogen
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What goes into the cathode compartment?
Oxygen
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What happens at the anode?
Hydrogen combines with hydroxide ions to make water and electrons. 2H(2) + 4OH(-) -> 4H(2)O + 4e(-)
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What happens at the cathode?
Oxygen gains electrons from the cathode and reacts with water from the electrolyte to make OH(-) ions. O(2) + 4e(-) + 2H(2)O -> 4)H(-)
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What is in between the anode and cathode?
A solution of potassium hydroxide, KOH, called the electrolyte
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Equation for rust?
Iron + water + oxygen -> hydrated iron(III) oxide
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What is a mole?
An amount of atoms or molecules of any substance that has a mass in grams equal to the relative formula mass.
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Number of moles =
(mass in g) / (Mr)
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Percentage composition of mass =
(Ar X No. atoms of that element) / (Mr of whole compound) X100
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How do you find out the empirical formula when you only know the mass of each element used, and the Ar?
Divide the masses by their Ar, multiply by 10 and the divide by the HCF
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Concentration=
(No. of moles) / (Volume in dm(3)=1 litre)
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What colour does lithium burn?
red
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What colour does sodium burn?
Orange
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What colour does potassium burn?
Lilac
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What are halogens?
Elements in group 7 that react with metals to make salts.
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Elements get more reactive in group 1...
as you go down the group.
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Elements get more reactive in group 7...
at the top of the group
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Where are transition elements?
Between group 2 and 3, they are typical metals
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Thermal decomposition equation..
metal carbonate -> metal oxide + carbon dioxide
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What colour is Copper(II) hydroxide?
Blue
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What colour is Iron(II) hydroxide?
Green/grey
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What colour is Iron(III) hydroxide?
Orange/brown
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What are the stages of water purification?
Filtration of big solids, Sedimentation - adding iron or aluminium sulfate which makes fine particles clump together and settle at the bottom, Chlorination to kill harmful bacteria and microbes
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What are 3 sources of water pollutants?
Nitrate residues from fertiliser run off. Lead compounds from old lead pipes. Pesticide residues.
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How do you test for sulfate ions in water?
Add dilute hydrochloric acid then 10 drops of barium chloride solution. If there's a white precipitate, there are sulfate ions.
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How do you test for halide ions in water?
Add dilute nitric acid then 10 drops of silver nitrate solution
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When testing for halide ions what colour precipitate will there be if there are chloride ions?
White
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Bromide ions?
Cream
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Iodide ions?
Pale yellow
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What is the contact process?
Burning sulfur in air to make sulfure dioxide, then oxidising it to make sulfur trioxide which is reacted with water to make sulfuric acid.
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What acids are ionised completely?
Strong acids, this means every hydrogen atom releases a hydrogen ion
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Why are some acids weak?
They are not fully ionised so only small numbers of H(+) are formed
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Other cards in this set

Card 2

Front

What do biological detergents do?

Back

they contain enzymes that help break down insoluble molecules into smaller soluble ones so you can wash clothes at lower temperatures.

Card 3

Front

Monounsaturated fats ...

Back

Preview of the front of card 3

Card 4

Front

Polyunsaturated fats..

Back

Preview of the front of card 4

Card 5

Front

What happens when you put unsaturated oil or fat in bromine?

Back

Preview of the front of card 5
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