chemistry LVI moles

amount of substance

quantity used to count atoms/other particles has symbol n and measured in mol

mole

amount of substance of a system which contains as many particles as there are atoms in 12g of carbon 12

avogadro’s constant

number of atoms in a mole of atoms

mole=

mass/Mr (molar mass)

number of moles (avogadro)

number of atoms/Avogadro’s constant

describe ideal gases

• molecules have continuous random motion

• no inter-molecular forces

• all collisions are perfectly elastic (total KE of particles doesn’t change)

• molecules have no size ie occupy 0 volume

Boyles law + charles’s law explained

• Boyles = V is directly proportional to 1/P

• charles’s = V is directly proportional to T

• equal volumes of all gases under the same conditions of temperature and pressure contain an equal an equal number of molecules

pV =

nRT

what do the variables mean in pV = nRT

• p = pressure of gas (Nm^-2 or Pa)

• V= volume of gas in m³

• n=amount of gas in mol

• R = universal gas constant (8.314 JK^-1mol^-1

• T= temperature of gas in K

0 kelvin

-273^oC

at RTP 1 mol of gas occupies

24dm³

RTP

• 25^oC

• 1 atm = 101,000 pa

cm³ → m³

1×10^-6

dm³ -> m³

1×10^-3

percentage yield

actual yield (mol)/theoretical yield (mol) x100

reasons for not 100% yield

• reaction has not gone to completion

• other (side) reactions may occur

• purification of product causes loss of product

atom economy

Mr of desired products/ Mr of all products x100

describe reactions with a high atom economy

• fewer waste products

• important to make best use of natural resources

• improved atom economy preserves raw material + reduces waster therefore increasing sustainability

Mol = (cm³)

V/24000

mol = (dm³)

V/24

concentration

mol/volume (dm³)

empirical formula how to find

mass or percentage/ Mr (divide by smallest then ratio)