Chemistry

Which of the following reactions is exothermic?

1. Na(s) --> Na(g)
2. Na(g) --> Na+ + e-
3. Cl2(g) --> 2Cl(g)
4. Cl(g) + e- --> Cl-1

My guess is 4, but I'm not sure

Here is what you do.
For 1, do we think it will take energy to change Na as a solid to Na as a gas. If you don't know much about Na, think about ice(that's a solid). Do you think it takes energy to melt the ice from a solid to a liquid, raise the temperature to boiling, then boil all the water to steam. Of course it takes energy to do that. If we must add energy it is endothermic. So Na(s) ==> Na(g) is an endothermic reaction and you don't check that one. Use that same kind of reasoning for 2,3, and 4.
For 2 you are removing an electron. For 3 you are separating two Cl atoms. In 4 you are adding an electron to an almost filled shell.

Thanks DrBob

exothermic reaction is one that releases heat. Adding an electron to a chlorine atom releases energy.

Cl(g) + e- Cl-(g)


Thanks Randy

asked by Fiona

Respond to this Question

First Name

Your Response

Similar Questions

  1. Chemistry

    I'm having a hard time understanding Endothermic and Exothermic reactions, like their standard format and stuff. For Exothermic reactions the heat is getting released into the surroundings, the products will be less than the
  2. Chemistry

    In a three reactions system the first two reactions are endothermic with DeltaH values of 138kj and 241kj. if the final reaction is exothermic what is the minimum value of DeltaH3 that would make the overall reaction exothermic?
  3. Chemistry

    In a three reactions system the first two reactions are endothermic with DeltaH values of 138kj and 241kj. if the final reaction is exothermic what is the minimum value of DeltaH3 that would make the overall reaction exothermic?
  4. Chemistry

    In a three reactions system the first two reactions are endothermic with DeltaH values of 138kj and 241kj. if the final reaction is exothermic what is the minimum value of DeltaH3 that would make the overall reaction exothermic?
  5. Chemistry

    Predict whether the following reactions would be spontaneous or not under standard conditions or if it's impossible to tell. 2 KClO3(s) + 3 C(s) --> 3CO2(g) + 2KCl(s) Exothermic 2 NO(g) + O2(g) --> 2NO2(g) Exothermic H2(g) +
  6. Chemistry

    Predict whether each of the following reactions would be exothermic or endothermic. a. CO(g) --> C(g) + O(g) b. 2H(g) + O(g) --> H20(g) c. Na+(g) + Cl-(g) --> NaCl(s) What is the sign of DH in each of these reactions?
  7. Chemistry

    Predict whether each of the following reactions would be exothermic or endothermic. a. CO(g) --> C(g) + O(g) b. 2H(g) + O(g) --> H20(g) c. Na+(g) + Cl-(g) --> NaCl(s) What is the sign of DH in each of these reactions?
  8. Chemistry

    Predict whether each of the following reactions would be exothermic or endothermic. a. CO(g) --> C(g) + O(g) b. 2H(g) + O(g) --> H20(g) c. Na+(g) + Cl-(g) --> NaCl(s) What is the sign of DH in each of these reactions?
  9. Chemistry

    Thank you for your rich explanation,but..... I don't get how "In this case both reactions are exothermic and the total is exothermic BUT both could be positive, both negative, or one each to give a final equation that is either +
  10. Science Help!

    A student made a list of reactions: Fireworks exploding Paper burning Cellular respiration How should the student title his or her list A. Double replacment reactions B. Single replacement reactions C. Endothermic reations D.
  11. biology (check answers)

    1. How do endothermic and exothermic reactions differ? a. Endothermic reactions release energy and are spontaneous. b. Exothermic reactions release energy and are spontaneous. c. Endothermic reactions give off heat and light. d.

More Similar Questions