Mini Lab 7.2 – Moles of Chalk

 

Purpose:  To determine the number of moles of chalk necessary to write your name.

 

Materials:

 

 

Procedure:

 

  1. Find the mass of a piece of sidewalk chalk.
  2. Go outside and write your full name on the pavement.
  3. Find the new mass of your piece of chalk.
  4. Find the mass of chalk used to write your name.

 

Data:

 

mass of chalk before writing your name =                      _____________ g

 

mass of chalk after writing your name =                         _____________ g

 

mass of chalk used to write your name =                       _____________ g

 

Data Analysis (Calculations):

 

  1. Determine the chemical formula of chalk (Hint on the anion – what group is calcium in on the periodic table? _________ ). Don’t forget a formula unit contains the lowest possible ratio of cations to anions to make the compound neutral.

 

 

chemical name

cation

anion

chemical formula

calcium carbonate

 

CO3 2 -

 

 

 

 

  1. Use a periodic table to fill in the following:

 

1 mol Ca = _______ g Ca       

 

1 mol C = _______ g C

 

1 mol O = _______ g O

 

 

  1. Determine the gram formula mass of calcium carbonate.
    1. Look at the chemical formula to determine the number of moles of each element necessary to form one mole of calcium carbonate.
    2. Convert moles to grams using dimensional analysis.
    3. Add grams of each element together.

 

_____ mol Ca  X                                 = ___________ g Ca

 

 

_____ mol C    X                                 = ___________ g C

 

 

_____ mol O    X                                 = ___________ g O

 

 

 

1 mol CaCO3   = ___________ g CaCO3

 

  1. Convert the mass of chalk used to write your name to moles of chalk.  Show your work using dimensional analysis.

 

 

 

 

 

Extension:

 

Show your work using dimensional analysis.

 

The pigment viridian (an intense bluish-green) is made of hydrated chromium oxide whose chemical formula is Cr2O.H2O.  If you use 15.6 g of viridian (which you have mixed with linseed oil) to paint a giant peace sign on your wall how many moles of viridium do you use? 

 

 

 

 

 

 

 

 

If 61 drops of linseed oil must be added to 2 grams of hydrated chromium oxide to make a good paint, how many drops of linseed oil did you use (round up to the nearest whole number)?