I am doing an elementary experiment regarding separating mixtures. My mixture contained NaCl, SiO2, and CaCO3. In the beginning, I calculated the mass of my mixture (all components together). As I completed the experiment, some of the elements were lost either by partial solubility or improper decantation / filtration techniques. In the end, I calculated each individual mass and found out (without surprise) that it does not equal the mass of the mixture from the beginning of the experiment.

If I were to calculate the % CaCO3 in the mixture, do I divide

mass of CaCO3 / total mass of mixture from the beginning

OR

mass of CaCO3 / the newly calculated total mass obtained from adding what I got for NaCl, SiO2, and CaCO3 throughout the experiment.

% CaCO3 in mixture = [(mass CaCO3 recovered)/(initial mass mixture)]*1-- \ ?

The mass recovered is not the mass you started with.

To calculate the percentage of CaCO3 in the mixture, you need to divide the mass of CaCO3 by the total mass of the mixture from the beginning of the experiment. Let me explain how to do it step by step:

Step 1: Determine the mass of CaCO3 you obtained at the end of the experiment.

Step 2: Find the mass of the mixture from the beginning of the experiment. This is the initial mass you calculated before starting the experiment.

Step 3: Divide the mass of CaCO3 by the total mass of the mixture from the beginning. This will give you the fraction of CaCO3 in the original mixture.

Step 4: Multiply the result by 100 to get the percentage. This will give you the percentage of CaCO3 in the original mixture.

It is important to use the total mass of the mixture from the beginning because you want to determine the percentage of CaCO3 based on the original composition of the mixture, not on the modified total mass obtained during the course of the experiment.

So, the correct calculation would be:

Percentage of CaCO3 = (mass of CaCO3 / total mass of mixture from the beginning) * 100

Remember to use the mass you calculated at the end of the experiment and the initial total mass of the mixture.