Determine the number of moles of calcium carbonate with 10% impurities, which reacts with 21.9 g of hydrochloric acid.

0.297 moles of calcium carbonate.

Solution:

Number of moles of HCl = moles

According to reaction

Two moles of HCl are reacting with one mole of , then 0.6 moles of HCl will react with:

=

Moles of calcium carbonate reacted = 0.3 moles

In 0.3 moles of calcium carbonate 10% impurities is present i.e.

of impurity.

Actual number of moles of calcium carbonate reacted = 0.3 - 0.003 = 0.297 moles.

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"