Chemistry C2

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  • Created by: Izzy
  • Created on: 16-05-13 15:32
explain why giant ionic lattices have high melting and boiling point
strong electrostatic forces of attraction - lots of energy required to pull apart
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explain the diffeence between diamond and graphite
diamond - linked to 4 carbons, strong intermolecular force, graphite - 3 C links, layers can slide over one another (soft, slippery)
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What is activation energy?
The smallest amount of energy that particles must have before they can react
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what are the 4 main factors that affect rate of reaction?
temperature, surface area, concentration of solutions, catalyst
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what is the effect of heat on a reaction?
higher temp = more energy = more particles collide more frequently
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what is the effect of high concentration/pressure on the rate of a reaction?
more particles = more likely to collide = speeds up
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catalysts are used up in a reaction, true or false?
false
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what is the difference between exothermic and endothermic?
exothermic = heat transferred from reaction, to surroundings, endothermic = takes in energy from surroundings
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What reaction is it when one is exothermic, and the other endothermic
reversible reaction
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What are exothermic reactions used for?
self heating cans, heat packs etc
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What is a base?
a substance that can neutralise an acid.
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what do acids produce when added to water?
H+ ions
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What do alkalis produce when added to water?
OH- ions
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how is a salt made? and what is the other product?
reaction of acid + metal. Hydrogen
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Give the general equation for a neutralisation reaction.
acid + base = a salt + water
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What are formed when you neutralise hydrochloric acid?
chlorides
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What are the salts called made by sulfuric acid?
sulfates
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What do nitric acids make?
nitrates
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How is a soluble salt made?
acid + alkali
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How is an insoluble salt made?
reacting two solutions of soluble salts
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what happens during electrolysis?
positive ions move to the negative electrode, negative ions to positive electrode
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why must ionic compounds be molten to be electrolysed?
so that the ions are free to move around
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what happens to positive and negative ions at the electrodes?
positive ions gain electrons to become neutral, negative ions lose electrons to become neutral
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OIL RIG means?
Oxidation is lost, reduction is gained
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in an aqueous solution, if two elements can be produced at an electrode, which one will?
The less reactive one
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Name 5 uses of aluminium
pans, power cables, aeroplanes, foil, drink cans
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what is the equation for the electrolysis of aluminium?
aluminium oxide --> aluminium + oxygen
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How do scientist reduce the temperature that aluminium is melted at?
by mixing it with cryolite
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how is carbon dioxide given off in electrolysis?
the oxygen atoms react with the hot, carbon electrolytes
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What are the 3 products of the electrolysis of brine? Uses for each?
chlorine gas (bleach), hydrogen gas (margarine) , and sodium hydroxide (soap)
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Why are substances electroplated?
To not use as much of the pure metal = cheaper, to protect them, looks better
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How does electroplating work?
The material to be plated is made the negative electrode, and the positive ions are attracted to it and cover it
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What is an isotope?
An atom of the same element, but with a different number of neutrons
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What is the relative mass of protons and neutrons?
1
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What is the atomic number?
the number of protons
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What is the mass number?
number of protons and neutrons in nucleus
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What do we use as a standard atom, and compare all other atoms to?
Carbon-12
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How do you work out the relative formula mass of a COMPOUND?
Add up the relative atomic masses of the elements in it
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What is a mole?
The relative formula mass of a substance, in grams.
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How do you work out the percentage of an element in a compound?
Mass of element ÷total mass of compound x 100
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What is the empirical formula?
The simplest whole number ratio of elements
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How do you work out the empirical formula?
Number of moles ÷ relative atomic mass - then put in ratio form
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In a balances equation, how to we find out the number of moles ?
By looking at the number in front of each element
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What is the yield of a chemical reaction?
The amount of products made
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How do you work out percentage yield of a substance?
amount of product produced ÷ maximum amount of product possible x 100
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Why do very few reactions have a 100% yield?
1. Reactant left on apparatus, Reactants not pure, difficulty separating from the mixture
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What is a reversible reaction?
When products can react together to make the reactants again
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Why are additives in food?
improve taste, colour and shelf life
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Explain the gas chromatography method?
Sample is vaporised, then a 'carrier' gas moves the vapour through the coiled column, The compounds in the sample with weaker attractions leave the column first, and so on. The time it takes for the gas to leave is the RETENTION TIME
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Explain 'mass spectrometry'
A mass spectrometer is connected to the gas chromatographer, and accurately measures the relative formula mass of a substance - produces a graph showing peaks called 'molecular ion peaks' , each peak is a difference substance
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What is nanoscience?
the study of small particles that are between 1 and 100 nanometres in size
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Give three uses of nanoscience
Glass can be coated with titanium oxide nano particles, titanium and zinc oxide nanoparticles used in suncream, face creams and deoderants, gold nanoparticles for tumors
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What are the possible risks of nanoscience?
Large surface area so if a spark occurs - large explosions could happen. Breathing in tiny particles could damage the lungs
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Card 2

Front

explain the diffeence between diamond and graphite

Back

diamond - linked to 4 carbons, strong intermolecular force, graphite - 3 C links, layers can slide over one another (soft, slippery)

Card 3

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What is activation energy?

Back

Preview of the front of card 3

Card 4

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what are the 4 main factors that affect rate of reaction?

Back

Preview of the front of card 4

Card 5

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what is the effect of heat on a reaction?

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