An oxygen tank kept at 20 ◦C contains 28 moles of oxygen and the gauge reads 31 atm. After two weeks, the gauge reads 10.5 atm. How much oxygen was used during the twoweek period? 1. 9.48 mol 2. 9.25 mol 3. 20.5 mol 4. 18.52 mol 5. 7.51 mol

Acalorimeter is to be calibrated: 51.203 g of water at 55.2 degree c is added to a calorimeter containing 49.783 g of water at 23.5c. after stirring and waiting for the system to equilibrate, the final temperature reached is 37.6 degree c. specific heat capacity of water (s = 4.18 j/g∙degree c). calculate the calorimeter constant. (smδt)warm water = -[(smδt)cold water + (calorimeterδtcold water)]