Question

1. In this experiment, what property of NaCl is used to separate it from the other two components? Is this a chemical or physical property? NaCl is the only compound in this mixture that is soluble in water, so its solubility in water is the property used to separate it. This is a physical property, because you are doing nothing to change the actual chemical composition. It's just solvated by water. 2. In this experiment, what property of CaCO3 is used to separate it from SiO2? Is this a chemical or physical property? The property of CaCO3 used to seperate it from SiO2 is its reactivity with acetic acid. By adding the acetic acid, you develop carbon dioxide (which bubbles out of solution), and CaCl2, which is soluble in water. You are undergoing a chemical reaction, so this is a chemical property. 3. An unknown sample of a mixture of salt and sand weighs 7.52 g before washing with water and 3.45 g after. What is the percent of sand in the sample? (Show all work.) 7.52g salt and sand, 3.45g sand, 4.07g salt (the difference in before and after water shows how much salt you had) 3.45 g sand / 7.52g total * 100 = 45.9% sand To check that this is correct, find the percentage of salt as well. 4.07g salt / 7.52g * 100 = 54.1% salt 45.9% + 54.1% = 100%. Everything is accounted for, so this must be the composition of the mixture.

Answer 1

Answer 1) In the mixture of sand, NaCl and $CaCO_{3}$ first separation was done by dissolving the mixture in water. In the first step the NaCl will get dissolved whereas, $CaCO_{3}$ will be undissolved and sand will settle at the bottom. Here, the physical property of solubility of NaCl in water is taken into consideration. The collected water is then filtered off and evaporated to get the NaCl back from the mixture with some loss. No chemical change occurs in case of NaCl extraction from water.

Answer 2) When $CaCO_{3}$ was to be removed from the undissolved part. The chemical property of $CaCO_{3}$ was used. Where it gets dissolved in acidic medium. And this way we can extract $CaCO_{3}$ and remove sand from it. We change the chemical composition of $CaCO_{3}$ by adding HCl to the mixture and dissolve $CaCO_{3}$ to form $CaCl_{2}$ which gets dissolved into the solution of HCl. Here, first decantation occurs and then extraction is done. Second, extraction is done using potassium carbonate in it which separates $CaCl_{2}$ from sand.

Answer 3) Here, Unknown mixture of salt and sand weighed =7.52 g (before washing);

Unknown mixture of salt and sand weighed =3.45 g (after washing);

To calculate the amount of salt in it, we can simply subtract the values of before and after washing change in weights.

The property of NaCl being soluble in water it will go away with washing leaving behind the sand only, after washing.

So, Weight of salt was = 7.52g - 3.45 g = 4.07g

To find the percentage of sand that was mixed with salt =

(3.45 g sand / 7.52g of mixture) X 100 = 45.9% sand was mixed with salt.

To verify whether the correct percentage of salt and sand was calculated we can recheck the value for salt as well.

(4.07 g of salt / 7.52g of mixture) X 100 = 54.1% salt

On adding we get, 45.9% + 54.1% = 100%.

Which confirms that the calculations are correct.