How many chlorine atoms are in 7MgCl2?

Iknow #2 is d. i just need to know why

Melting and boiling are endothermic processes. this means that these processes absorb energy from their surroundings in order to occur. use this information and the data you collected in the phase change gizmo to describe what happens to the temperature of water when you boil it, then explain why this result occurs.

In the lab, ammonia was mixed with water to form ammonium hydroxide. what is/are the reactant(s)? o water and ammonia o ammonia o ammonium hydroxide need