Module 2: Atoms and reactions Flashcards
(46 cards)
What is relative atomic mass?
Relative atomic mass is the average mass per atom of the naturally occurring form of an element relative to 1/12th of the mass of a carbon-12 atom.
What is relative isotopic mass?
Relative isotopic mass is the mass of an atom of an isotope relative to 1/12th of the mass of a carbon-12 atom.
What is relative molecular mass?
Relative molecular mass is the sum of the relative atomic masses of the constituent atoms of a molecule relative to 1/12th of the mass of a carbon-12 atom.
What is the equation for calculating the relative atomic mass (Ar) of an isotope?
Ar = { ( abundance of isotope x isotopic mass of isotope ) /100
What is the equation linking molar mass, mass and number of moles?
number of moles = mass (g) / Mr (g/mol)
What is meant by the molar mass?
The mass per mole of a substance
What number represents Avogadro’s constant?
6.02 x 10*23
What is the empirical formula?
The empirical formula is the formula showing the simplest whole number ratio of atoms of each element present in a compound.
What is the molecular formula?
The molecular formula is the formula showing the actual number of atoms of each element in a molecule.
What is stated by Avogadro’s law?
At the same temperature and pressure, 1 mole of any gas will occupy the same volume.
What is standard temperature and pressure?
Pressure = 1 Atmosphere = 100,000Pa
Temperature = 25*C = 298 K
What is the equation for number of moles using volume (in dm cubed and cm cubed) at RTP?
moles = volume/molar volume
number of moles = volume (dm cubed) / 24
number of moles = volume (cm cubed) / 24000
What is the ideal gas equation?
PV = nRT
P = pressure in Pa
V = volume in m cubed
dm cubed / 103 = m cubed
cm cubed /106 = m cubed
n = number of moles
R = universal gas constant = 8.314 Jmol-1K-1
T = temperature in K
T(K) = T(*C) + 273
What does the % yield of a chemical reaction show?
The % yield of a chemical reaction shows how much product was actually made compared with the amount of product the was expected
What is the equation for % yield?
% yield = actual yield (g) / theoretical yield (g) x 100
What are some reasons as to why yield is not often 100%?
- the reaction may be incomplete
- side reactions may occur, leading to by-products
- reactants may not be pure
- some reactants/products may be left behind in the apparatus
What is atom economy?
Atom economy is the % of reactants that end up as useful products
What is the equation for atom economy?
Atom economy = mass of wanted product (s) / total mass of all products x 100
What is the equation linking concentration, moles and volume?
Conc. (moles.dm-3) = moles / volume (dm3)
What is concentration?
A measure of how much solute is dissolved per solvent.
What is meant by hydrated?
Hydrated refers to a crystalline compound containing water molecules.
What is meant by anhydrous?
Anhydrous refers to a substance that contains no water molecules.
What is water of crystallisation?
Water molecules that are within the crystalline structure of the compound.
Why do different isotopes of the same element react in the same way?
- chemical reactions involve electrons, and isotopes have the same number and arrangement of electrons
- neutrons make no difference to chemical reactivity