chem definitions Flashcards

(41 cards)

1
Q

isotopes

A

are atoms of the same element with different numbers of neutrons and different masses

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2
Q

relative isotopic mass

A

is the mass of an isotope relative to 1/12 th of the mass of an atom of carbon - 12

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3
Q

relative atomic mass

A

is the weighted mean mass of an element relative to 1/12 th of the mass of an atom of carbon - 12

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4
Q

avogadro’s constant

A

6.02 x 10^23

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5
Q

molar mass

A

is the mass per mole of a substance (g mol^-1)

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6
Q

molecular formulae

A

the number of atoms of each element in a molecule

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7
Q

empirical formulae

A

is the simplest whole-number ration of atoms of each element in a compound

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8
Q

relative molecular mass

A

compares the mass of a molecule with the mass of an atom of carbon-12

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9
Q

relative formula mass

A

compares the mass of a formula unit with the mass of an atom of carbon-12

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10
Q

molar gas volume

A

is the volume per mole of gas molecules at a stated temperature and pressure

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11
Q

room temperature and pressure (RTP)

A

25 degrees Celsius / 298 K

101 kPa / 1 atm pressure

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12
Q

ideal gas equation

A
pV = nRT
pressure (Pa)
volume (m^3)
amount of gas molecules (mol)
R = gas constant (8.31 J mol^-1 K^-1)
temperature (K)
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13
Q

celcius to kelvin

A

+ 273

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14
Q

kPa to Pa

A

x 10^3

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15
Q

percentage yield

A

= (actual yield) / (theoretical yield)

x100 for percentage

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16
Q

atom economy

A

is a measure of how well atoms have been utilised

= (sum of molar masses of desired products) / (sum of molar masses of all products)
x100 for percentage

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17
Q

strong acids

A

e.g HCL

releases all its hydrogen atoms into solution as H+ ions completely dissociates in aqueous solutions

18
Q

weak acids

A

e.g ethanoic acid (CH3COOH)
only releases a small proportion of its available hydrogen atoms into solution as H+ ions.
partially dissociates in aqueous solution

19
Q

alkali

A

is a base that dissolves in water releasing hydroxide ions (OH-) into the solution

20
Q

acid + alkali

A

= salt + water

21
Q

ionic bonding

A

is the electrostatic attraction between positive and negative ions.
it holds together cations and anions in ionic compounds

22
Q

properties of ionic compounds

A

have high melting and boiling points
tend to dissolve in polar solvents: water
conduct electricity only in liquid state or in aqueous solution

23
Q

covalent bonding

A

is the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

24
Q

dative covalent bond

A

is a covalent bond in which the shared pair of electrons has been supplied by one of the bonding atoms only.

25
electronegativity
the attraction of a bonded atom for the pair of electrons in a covalent bond
26
intermolecular forces
are weak interactions between dipoles of different molecules split into 3 categories: induced dipole-dipole interactions, permanent dipole-dipole interactions hydrogen bonding
27
induced dipole-dipole interactions (london forces)
are weak intermolecular forces that exist between all molecules
28
permanent dipole-dipole interactions
act between the permanent dipoles in different polar molecules
29
simple molecular substance
= is made up of simple molecules - small units containing a definite number of atoms with a definite molecular formula
30
ionisation energy
measures how easily an atom loses electrons to form positive ions
31
first ionisation energy
is the energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions
32
disproportionation
is a redox reaction in which the same element is both oxidised and reduced
33
enthalpy
is a measure of the heat energy in a chemical system
34
enthalpy change
= enthalpy of products - enthalpy of reactants
35
activation energy
the energy input required to break bonds acts as an energy barrier to the reaction is the minimum energy required for a reaction to take place
36
standard enthalpy change of reaction
is the enthalpy change that accompanies a reaction in the molar quantities shown in a chemical equation under standard conditions, with all reactants and products in their standard states
37
enthalpy change of formation
is the enthalpy change that takes place when one mole of a compound is formed from its elements under standard conditions, with all reactants and products in their standard states
38
standard enthalpy change of combustion
is the enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions, with all reactants and products in their standard states
39
standard enthalpy change of neutralisation
is the energy change that accompanies the reaction of an acid by a base to form one mole of h20(l), under standard conditions, with all reactants and products in their standard states
40
specific heat capacity | water?
is the energy required to raise the temperature of 1g of a substance by 1K water = 4.18 J g^-1 K^-1
41
calculating energy change formulae
q = mcT ``` q = heat energy m = mass that changes temperature c = specific heat capacity T = temperature change ```