1) An endothermic reaction is a reaction where heat is "absorbed" and the surrounding area is cooled. An example of an endothermic reaction is the classic baking soda and vinegar reaction. The mixture gets cold.
An exothermic reaction is one which gives off heat, such as burning, which is itself a chemical reaction.
2) (I don't actually know this one but i hope i helped with number one)
The gram-formula mass means that the mass of one mole molecule. Then you just need to calculate the elements together. So the gram-formula mass of (NH4)3PO4 is equals to (14+4)*3+31+16*4= 149g/mol. So the answer is (c)
I believe that the answer is B. The protons have a positive charge (pro=positive), neutrons have no charge because the are neutral (neutral=positive and negative), and electrons are negative
