The third one, it releases H+ions into a solution.
The third one down: "When barium hydroxide is mixed with ammonium chloride, ice crystals form on the outside of the container."
This is because an endothermic reaction [process] takes in more energy than it releases. Therefore because a decrease in energy leads to a decrease in temperature, the ice crystals forming show that it must be a endothermic reaction [process].
Hope this helps! :)
AJ
<span>Air pressure decreases as you move higher in the atmosphere. Think of a column of air directly over your body. ... Just as air pressure decreases with altitude, so does the density of air.</span>
