Calculation to Determine Number of Moles Needed to Write a Quote


Problem: How many moles of calcium carbonate (CaCO3) are needed to write the following: “ ‘Obstacles are those frightful things you see when you take your eyes off your goal.’ ~Henry Ford”.


Independent Variable

Length and size of quote

Dependent Variable

Amount of calcium carbonate (in moles) used

Controlled Variables

Piece of chalk used

Surface quote was written on

Size of letters (relatively)

Ruler used to measure chalk



     A 4.5 cm piece of purple chalk was obtained for the purpose of writing the quote. The purple piece of chalk was weighed (in grams) using an electronic balance. The mass of the chalk was found to be 11.03 grams. This piece of chalk was the only piece used in this experiment. A square section of sidewalk was chosen, and the quote was written on the concrete. The quote was only written on this piece of concrete. The letters of the quote were written relatively large (each letter averaging approximately 18.25 centimeters). The size and font of the letters were not varied (intentionally).

     After writing the quote, the chalk was weighed again using an electronic balance. It was measured using the same ruler as before and found to be 2.3 centimeters. The chalk now had a more spherical appearance rather than the previous cylindrical appearance. The mass of the chalk after having written the quote was found to be 2.72 grams. The amount of moles needed to write the quote calculated to be .083 moles.






4.5 centimeters

2.3 centimeters


11.03 grams

2.72 grams


Cylindrical. Relatively uneven at top with one side of the top steeper than the other side.

Rounded and more spherical. One side of the top of the chalk was steeper than the other side due to the way the chalk was used.



mass of chalk before writing quote – mass of chalk after writing quote = amount of chalk used (in grams)

11.03 grams – 2.72 grams = 8.31 grams used

grams of CaCO3 (1mol CaCO3/ molar mass CaCO3) = mass CaCO3 in moles

8.31 grams CaCO3 (1mol/ 100.1 grams CaCO3) = .083 moles CaCO3 used




            In this lab, the number of moles of calcium carbonate needed to write the following were found: “Obstacles are those frightful things you see when you take your eyes off your goal.” ~Henry Ford. The quote required .083 moles of calcium carbonate. Based on these results, it can be concluded that only a small amount of calcium carbonate was needed to write the quote. This is evident considering one mole of calcium carbonate is 100.1 grams and only 8.31 grams of calcium carbonate were needed to complete the quote.

            A limiting factor of this experiment was that the mass of calcium carbonate before and after writing the quote were both less than the actual mass. This is because some of the chalk was left on fingers and therefore would not make the actual mass of calcium carbonate accurate. To avoid this problem, it is possible to wrap the chalk in some light material and then to weigh that material before putting the chalk in and after the quote is written. The mass of the material after the chalk was inserted would be slightly greater than the material by itself. The difference between the two would allow for the rest of the chalk to be accounted for.