Chemistry 2a Flashcards

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  • Created by: Evie
  • Created on: 16-04-13 20:36
How can you work out the relative molecular mass in a GC-MS graph?
Read off from the molecular ion peak
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Advantages of using instrumental methods?
Fast, sensitive and accurate!
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What is retention time?
The time substances in a GC-MS take to reach the detector
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Why can't yields be 100%?
The reaction is reversible - unexpected reactions - products lost in equipment or through filtration
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What is the equation for percentage yield?
(actual yield / predicted yield) x 100
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How do you find the empirical formula?
List all elements in the compound. Write the experimental masses. Divide each by the Ar. Find a ratio.
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Percentage mass of an element in a compound - equation?
(Ar x no. of atoms of element / Mr) x 100
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Whats the difference between Ar and Mr?
Ar is the mass number and applies to individual elements, Mr is just all the Ar's added together
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What is one mole of a substance?
One mole of a substance is equal to its Mr in grams. Eg - Iron has an Ar of 56, so one mole of iron weighs 56g.
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What is the mass number and atomic number?
Atomic number is the number of protons. Mass number is the total protons and neutrons.
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Masses of particles?
Proton 1, Neutron 1, Electron 1/2000 (very small)
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What is an isotope?
Different atomic forms of the same element with the same number of protons but a different number of neutrons. Eg carbon-12 and carbon-14
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What happens in ionic bonding?
Atoms lose or gain electrons to form charged particles (ions) which are strongly attracted to each other
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What structures do ionic compounds form? What properties do they have?
Closely packed regular lattice arrangements. High boiling/melting points as the strong attraction between ions need lots of energy to break. They dissolve easily in water and move freely in a solution, carrying electric current.
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Which groups are most likely to form ions? Why?
Groups 1&2 and 6&7(halogens) because they only have to lose/gain 1/2 electrons
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What is covalent bonding? Give 7 examples.
Sharing electrons. Hydrogen, chlorine, methane, water, oxygen, hydrogen chloride and ammonia (nitrogen/hydrogen)
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What are the properties of simple molecular substances?
Strong covalent bonds between atoms but very weak forces of attraction between each molecule. Low melting/boiling points. Mainly gases or liquids. Don't conduct electricity as there are no ions.
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What are the properties of giant covalent substances? Give 3 examples.
Don't conduct electricity except graphite when molten. High melting/boiling points. Diamond, graphite and silicon dioxide.
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What are the properties of metallic structures?
Good heat/electricity conductors from free electrons, strong electrostatic forces, can be bent and shaped.
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What is an example of a new material and what can it be used for?
Nitinol is an alloy of nickel/titanium. Its a shape memory alloy which you can twist into shape. If you heat it enough it goes back to its normal shape. Used for braces and glasses frames.
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What are nano particles? What are fullerenes? Nanotubes?
Tiny particles containing hundreds of atoms. They include fullerenes which are molecules of carbon shaped like hollow tubes or balls. They can be joined to form nanotubes which are very strong.
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Uses of nano particles?
Huge surface area to volume ratio which could be used for catalysts, stronger and lighter building materials. As they conduct electricity they can be used for electric circuits in computer chips. Easy absorbing nano medicine.
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What determines the properties of a plastic?
The bonds between the molecule chains
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Explain weak forces in polymers
Individual tangled chains of polymers, held together by weak intermolecular forces are free to slide over each other.
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Explain strong forces in polymers
Strong intermolecular forces have cross links which hold the chains firmly together.
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What are thermosoftening polymers?
No crosslinks, easily melted. When it cools, the polymer hardens into a new shape. You can melt and remould over and over.
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What are thermosetting polymers?
Crosslinked, solid structure, doesn't soften when heated, strong, hard and rigid.
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How is low density polythene made? What is it used for?
Heating ethene to 200 degrees under high pressure. Its flexible - used for bags and bottles.
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How is high density polythene made? What is it used for?
Made at a lower temperature and pressure with a catalyst. Its more rigid so its used for water tanks and drainpipes.
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Other cards in this set

Card 2

Front

Advantages of using instrumental methods?

Back

Fast, sensitive and accurate!

Card 3

Front

What is retention time?

Back

Preview of the front of card 3

Card 4

Front

Why can't yields be 100%?

Back

Preview of the front of card 4

Card 5

Front

What is the equation for percentage yield?

Back

Preview of the front of card 5
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