Question

1- If the following processes take place at constant pressure, which will be exothermic and which will be endothermic?

I. Gasoline burns.

II. Two solids at room temperature are mixed and the temperature of the mixture decreases to 15 °C   

( please expline why did you choose your anwser)

2-What is the correct ranking of the electrostatic potential energy of the following systems, starting with the one with the lowest energy?

I an electron that is 2.8 nm from a +2 cation

II an electron that is 2.8 nm from a –2 anion

III an electron that is 2.8 nm from a proton A. I < III < II

B. I = II < III

C. II < III < I

D. II < I < III

E. III < II = I

(please explain why did you choose your answer)

Answer 1

1.I) Exothermic. Combustion(burning) releases lot of heat i.e., it is an exothermic process.

II) Endothermic. Since the temperature of the mixture falls, the mixture has absorbed heat from surroundings.

2)

Thus the correct order of potential energy is I < III < II. Option A.