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)
You answer this by using the pH formula and and the relation of pH and pOH, pH = -log[H+] and 14 = pH + pOH. The correct classification are as follows:
<span>A. [H2O+]=6.0x10^-12
basic
B. [H3O+]=1.4x10^-9
basic
C. [OH-]=5.0x10^-12
acidic
D. {OH-]=3.5x10^-10
acidic
Hope this answers the question.
</span>
1) Carbon-13:
Proton-6 Neutron-7 Electron-6
2)Atomic mass of element X:
(55*10+56*20+57*70)/100=56.6
