I need examples that we do in everyday life ?? Help please

Dumbledore decides to gives a surprise demonstration. he starts with a hydrate of na2co3 which has a mass of 4.31 g before heating. after he heats it he finds the mass of the anhydrous compound is found to be 3.22 g. he asks everyone in class to determine the integer x in the hydrate: na2co3·xh2o; you should do this also. round your answer to the nearest integ

If you are told to get 100 ml of stock solution to use to prepare smaller size sample for an experiment, which piece of glassware would you use?

Why is it incorrect to balance a chemical equation by changing the subscripts? explain.