Blackboard chalk contains a certain percentage of calcium carbonate. If a 1.51 g piece of chalk produces 0.665 g of carbon dioxide, what percentage of calcium carbonate is chalk?

The percentage of Calcium carbonate in chalk = 100%

Given

1.51 g piece of chalk produces 0.665 g of carbon dioxide

Required

percentage of calcium carbonate

Solution

Reaction

CaCO3 (s) + 2 HCl (aq) → CaCl2 (aq) + H2O (l) + CO2 (g)

mol CO2 :

= 0.665 g : 44 g/mol

= 0.015

From the equation, mol CaCO3 = mol CO2 = 0.015

mass CaCO3 :

= mol x MW

= 0.015 x 100

= 1.5 g

in theory, limestone is composed principally of the compound calcium carbonate - caco3, but in reality this compound is deposited in conditions involving a number of other compounds as impurities so it ends up being a mixture of many compounds.

hope this : -)

tony (lordcaos066)