100.0 mL of a solution with a concentration within 10% of 0.1223 M NaCl (or anot

Question

100.0 mL of a solution with a concentration within 10% of 0.1223 M NaCl (or another salt) solution by weighning a calculated amount of solid sodium chloride accurately on a scale and doing the procedure for it. Procedure is transferring it to a 250 mL beaker and disolving it in 75 mL of distilled water. We then transfer the solution from the beaker to a 100 mL volumetric flask. Finally we add water in smaller portions to the volumetric flask to fill the flask to the volumetric mark.

My question: what is the calculated weight? Is the weight from the solid salt itself or do I use the molarity?

My weight for the solid NaCl: 151.9 grams.

Do I just take 15.19 grams?

Thanks!!

Explanation / Answer

Any procedure of solution preparation will not change the mass of salt initially taken. what you are changing is the concentration of salt in solution. But the original salt weight would remain the same If you do a back calculation from the end solution you prepared. Unless you are being specifically asked for concentration of salt in diluted solution, the weight would remain same as taken. So you are right. Take the mass initially taken.

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