quantative chemistry

• relative atomic mass is $A_r$

  • using the average mass of an atoms isotopes to give the mass on an atom

  relative formula mass is $M_r$

  • sum of relative atomic mass in a formula
  • do not use the big number eg. $2C_2O$
• $\%\ by\ mass\ =$$\ \frac{total\ mr\ of\ that\ element}{mr\ of\ the\ compound}\cdot100$
• calculating moles of an element eg: carbon

  • Ar of carbon is 12
  • 12g of carbon = 1 mole of carbon atoms
  • in 12g of carbon theres 1 mole of carbon atoms is 6.02 $\cdot$ 10 $^{23}$ carbon atoms
• calculating moles:

  $moles=$$\frac{mass\left(g\right)}{Ar}$

  
  

  moles = mass divided by Ar or Mr
• using moles to balance equation:

  1. find the moles of each compound using the equation mole=mass/mr
  2. write it before each compound as a big number
  3. then divide each mole by the smallest one as your final big number ygmmmm
  4. make sure you remove the big 1s
• concentration (g/dm $^3$ ) = $\frac{mass}{volume}$
• concentration = mass divided by volume
• why 100% yeild is not always possible:

  • products may be lost when reactants are seperated from the mixture
  • reaction may react in an unexpected way
  • reversible reactions may not go to completion
• why is atom economy important

  • saves money
  • increases sustainabilty
• concentration tells us the mass of a solute in a given volume
• concentration = moles/volume
• 1 mole of gas occupies 24dm^3
• room temperature is 20 degrees celcius

  room pressure is 1 atmosphere
• limiting reactant

  • mass
  • mr
  • mole
  • ratio
• titration

  • concentration (crazy)
  • volume (victor)
  • moles (makes)
  • ratio (robots)
• percentage by mass is what percent of the mr is due to one of the element is in the compound
• molar volume of a gas

  
  

  volume = mole times 24
• atom economy is the amount of starting reactants that ends up useful products