Neodymium and dysprosium are two REEs that are considered “Critical Elements” in the medium-term (2015–2025). Explain why these two elements are considered important for present and future clean energy technologies and why there is a supply risk associated with those elements.

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)]