Aburning candle is covered by a jar as shown in the picture. the whole arrangement has a mass of 500 g. what will be the approximate mass of the arrangement when the candle is completely burnt, after four minutes? a) 0 g b) 50 g c) 250 g d) 500 g

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