ChemistryII (Percent Composition)
posted by jezzaD. .
1. Identify the percent composition of sodium carbonate.
2. Determine the percent composition of calcium in calcium carbonate.
Pls. help me... my prob is that there is something in the solution that bothers me.. pls.kindly show me how to do.. i'll thank u later... :)

In your first question, 1 mole of sodium carbonate=2 moles of sodium=1 mole of carbon =3 moles oxygen. Take the moles for each of the components in sodium carbonate and multiply them by their respective molecular weights e.g. 3 moles of oxygen* 15.999g/mole to calculate the weight of oxygen in sodium carbonate. Since the molecular weight of sodium carbonate is 105.9784 g/mol, the weight that you calculate for oxygen divided by the the molecular weight of sodium carbonate multiplied by 100 will give you the percent composition of oxygen in sodium carbonate ([weight of oxygen/105.9784] *100); perform these steps for each of the additional components in sodium carbonate.
The answer to the second question is the same, but you only need to do the steps mentioned above with Ca. 1 mole of Ca= 1 mole of calcium carbonate. Take the molecular weight of Ca and divide it by the molecular weight of calcium carbonate, which is 100.0869 g/mol. Remember to multiply that number by 100 to get percent. 
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