20. What mass of oxygen is needed to react with 6.15 g of magnesium? 2 Mg +1 02 → 2 Mgo
a. 8.10 g 02
b. 3.08 g 02
c. 2.25 g 02
d. 4.05 g 02

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)]