chemical formulae, equations and calculations part 1

• True or False? A balanced chemical equation has the same number of atoms of each element on both sides.

  True
• What numbers are missing to balance this equation?

  .....H2O2 .....H2O + ..... O2

  2 H2O2 -- > 2 H2O + O2
• What is the relative formula mass of CuCO3?

  123.5
• what does moles mean?

  an amount of something that contains Avogadro's number of particles
• what is avogadro's number

  6.02 x 10^23
• formula for moles

  Mass / Mr
• How many moles are in 45.0 g of water?

  Mr H2O = 18.0

  2.5 mol
• Calculate the mass of 0.25 moles of copper carbonate, CuCO3.

  Mr CuCO3 = 123.5 (HINT use the equation mass = moles x molar mass just moles equation rearranging)

  30.9 grams
• define percentage yield


  the % of product you make compared to how much could be made ever / last atom reacted
• define actual yield

  the amount we actually get
• define theoretical yield

  we'd expect to get based on our calculations
• State the equation for percentage yield.

  actual yield divided by theoretical yield ( x 100)
• If the actual yield is 1.50 g and theoretical yield is 2.00g, what is the percentage yield?

  75%
• reasons why you do not get 100% yield

  - Some product is lost.

  - not all reactants turn into products ( incomplete reaction)

  - Alternative reaction occurred
• define empirical formulae

  the simplest ratio that atoms in a compound can be expressed as
• define molecular formulae

  shows the actual number of atoms of each type of element in a molecule