To use Charles' Law, which of the following needs to remain constant? A. Temperature and volume
B. Temperature and the number of moles of a gas
C. Pressure and volume
D. Pressure and temperature E. Pressure and the number of moles of a gas

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