Many first aid kits include an instant cold pack. A cold pack utilizes a chemical reaction that has a significant change in energy in order to make the pack feel cold. Explain which type of reaction, an endothermic reaction or an exothermic reaction, would be most useful for making a cold pack.

Asample of silver (with work function ? = 4.52 ev) is exposed to an ultraviolet light source (? = 200 nm), which results in the ejection of photoelectrons. what changes will be observed if: silver is replaced with copper (? = 5.10 ev) more photoelectrons ejected no photoelectrons are emitted fewer photoelectrons ejected more energetic photoelectrons (on average) less energetic photoelectrons (on average)

Iknow the answer to 13 is b and 14 is d. i just need to know why the correct answers are correct

Answer asap need by wednesday morning calculate the ph of 0.036m naoh best answer will be brainliest