Amount of substance

Question 1

Relative atomic mass (Ar)

Answer 1

The weighed average mass of an atom, taking into account its naturally occurring isotopes, relative to 1/12 the RAM of carbon-12
Ar=(average mass of one atom of an element)/(1/12 mass of one atom of C-12)

Question 2

Relative molecular mass (Mr)

Answer 2

(of a molecule) is the mass of that molecule compared to 1/12 the RAM of C-12
Mr=(average mass of one molecule)/(1/12 mass of one atom of C-12)
Also calculated by adding up the relative atomic masses of all atoms present in the molecule

Question 3

Avogardo constant

Answer 3

Number of atoms in 12g of carbon-12 is 6.022*10^23

Question 4

Mole

Answer 4

amount of substance that contains 6.022*10^23 particles (entities)

Question 5

Mole equation

Answer 5

mass (g) = Mr * no. of moles

Question 6

Limiting reactant

Answer 6

The reactant in a chemical reaction that determines the amount of product produced during the reaction. Not in excess

Question 7

Ideal gas equation

Answer 7

pV=nRT
p= pressure (Pa)
V= volume (m^3)
n= number of moles
R= gas constant ( 8.31Jk^-1mol^-1)
T= temperature (K)

Question 8

Atom economy

Answer 8

measure of the amount of starting materials that end up as useful products. Important for sustainable development and for economic reasons reactions with higher AE are used
AE(%)=(total Mr of desired product)/(total Mr of reactants) *100
Mr= including multipliers
AE doesn’t change with mass

Question 9

Percentage yodel

Answer 9

mass of product obtained compared to the theoretical maximum mass calculated from a balanced equation.
% yield= (mass of product actually made)/(maximum theoretical mass of product) *100

Question 10

Empirical formula

Answer 10

simplest whole number ratio of atoms of each element in a compound. 1) Find masses of each of the elements in a compound (mass or %). 2) Calc. no. of moles by dividing mass or % by Ar of element 3) Find simplest whole number ratio by dividing by smallest no. then multiplying to get a whole number

Question 11

Molecular formula

Answer 11

actual no. of atoms of each element in one molecule of a compound. 1) Calculate Mr of empirical formula 2) Divide given Mr by Mr of empirical formula 3) Use this number to multiply by EF to get MF