Module 2: Foundations in chemistry.

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Define isotope.
Atoms of the same element, which react in the same way, with different numbers of neutrons and different masses.
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Define relative isotopic mass.
The mass of an atom compared with 1/12th of the mass of a carbon-12 atom.
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Define relative atomic mass.
Weighted mean mass of an atom of an element compared with 1/12th of the mass of a carbon-12 atom.
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Define mole.
A mole is the amount of substance containing as many 'particles' as there are carbon atoms in exactly 12 grams of the carbon-12 isotope.
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Define molar mass.
Sum of all the relative atomic masses of each atom/ion in a formula.
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Define empirical formula.
The simplist whole number ration of atoms of each element present in a compound.
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Define molecular formula.
The actual number and type of atoms of each substance in a molecule.
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How to calculate the percentage of an element in a compound?
((Ar of element)x(no. of elements if formula))/Mr of compound
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How to calculate the empirical formula?
Relative molar mass/formula mass of empirical formula.
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What is water of crystallisation?
The water molecules that form an essential part of the crystalline structure of a compound.
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Define concentration.
The amount of solute, in moles, dissolved per 1dm3 of solution.
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What is the ideal gas equation?
pV=nRT, p-pressure in pascals, v-volume in dm3, n-moles, r-universal gas constant, t-temp in k (o degree=273 k)
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How to calculate percentage yield?
(Actual amount in mol of product/theoretical amount in mol of product) x 100
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What is percentage yield?
A measure of success of lap prep - does it go to completion, inpure reactants, by-products, separation and purification, reactants/products left in apparatus.
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What are the limitations of percentage yield?
A high % yield may still produce significant by-products that may be wasted and incur disposal cost, or may be sold and used in other processes.
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How to calculate atom economy?
(Molecular mass of wanted products/sum of molecular mass of all products) x 100
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What is atom economy?
A description of the efficiency of the reaction considering both the desired and unwanted products.
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Define a salt.
Ionic compounds that are produced when a H+ ion from an acid has been replaced by a metal or other positive ion.
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Define atomic orbital.
Region around nucleus that can hold up to two electrons with opposite spin.
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Describe s-orbitals.
Spherical shape, from n=1 each shell contains 1 s-orbital, holds up to two electrons.
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Describe p-orbitals.
Dumbbell shape, from n=2 each shell contrails 3 p-orbitals, holds up to 6 electrons.
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Describe d-orbitals.
From n=3 each shell contains d-orbitals, hold up to 10 electrons.
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Describe f-orbitals.
From n=4 each shell contains 7 f-obtains, hold up to 14 electrons.
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Describe oxidation.
The loss of electrons or an increase in oxidation number.
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Describe reduction.
The gain of electrons or a decrease in oxidation number.
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Define ionic bonding.
Electrostatic attraction between positive metal ions and negative non-metal ions.
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Describe the structure of ionic compounds.
Giant ionic lattices resulting from oppositely charged ions attracted strongly in all directions, that are soluble in polar solvents.
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Define covalent bonding.
Strong electrostatic attraction between a shared pair of electrons and nuclei of the bonded atoms (attraction between nuclei and electrons overcome repulsion of the electrons.
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Define average bond enthalpy.
Measurement of covalent bond strength.
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Define dative/coordianate bond.
One atom that supplies both electrons to the covalent bond e.g. NH4+.
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Define lone pairs.
Concentrated areas of negative charge around the atom which are not involved in chemical bonding but decrease bond angles by 2.5 degrees as they are more electron dense.
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Define electronegativity.
Ability of an atom to attract bonding electrons in a covalent bond.
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Define polar bond.
A covalent bond between 2 atoms where one atom is more electronegative so has a greater attraction for the shared electrons.
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Define permanent dipole.
A difference in charge that is always present across a molecule caused by differences in electronegativities that do not cancel out.
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Define polar molecule.
A molecule with polar bonds that do not cancel out due to their directions.
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Define overall dipole.
Polar bonds which are cancelled out because of the shape of a molecule.
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Define intermolecular forces.
Weak attractions affecting physical properties of a substance.
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What are London forces?
The weakest I.M forces (increased by no. of electrons) caused by random movement of electrons in atoms' shells causing imbalance of negative charge at any one point, (instantaneous-instantaneous dipole).
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What are pemenant-induced dipole interactions?
Polar molecules cause electrons to shift slightly in neighbouring molcule by being repelled or attracted, making a non-polar molecules slightly polar.
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What are permenant-permenant dipole interactions?
Molecules with permanent dipoles attract others with permanent dipoles.
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Define hydrogen bonding.
Strong dipole-dipole attractions between an electron deficient hydrogen atom and a lone pair of electrons on another atom that is highly electronegative e.g. -NH, -OH or -HF.
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Describe the structure of simple covalent molecules.
Simple molecular lattices as covalently bonded molecules attracted by I.M forces, that are soluble in non-polar solvents (London forces form between solvent and molecules to weaken the lattice structure.)
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Other cards in this set

Card 2

Front

Define relative isotopic mass.

Back

The mass of an atom compared with 1/12th of the mass of a carbon-12 atom.

Card 3

Front

Define relative atomic mass.

Back

Preview of the front of card 3

Card 4

Front

Define mole.

Back

Preview of the front of card 4

Card 5

Front

Define molar mass.

Back

Preview of the front of card 5
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