July 29, 2014

Homework Help: Chemistry

Posted by Fiona on Monday, April 30, 2007 at 10:42pm.

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

Answer this Question

First Name:
School Subject:

Related Questions

Chemistry - Redox reaction of cl2 --> cl ion and clo2- I split it up into two...
Chemistry ,Reactions at Electrodes during Electrol - Reactions at Electrodes ...
chem-balancing acidic equation - the reaction: Cr2O7^-2(aq) + Cl- -> Cr^3+(aq...
Chemistry - Calculate the energy changes associated with each of the following ...
chemistry - Write the half reaction and balanced equation for: Cl2(g) + H2(g) -&...
Chem - Which of the following produces a coordinate complex? H2SeO4 + 2Cl- + 2H...
Chemistry - I'm having a hard time understanding Endothermic and Exothermic ...
chemistry - Which equation describes the relationship between the rates at which...
chemistry(check my answer) - Which equation describes the relationship between ...
chemistry(check my answer) - Which equation describes the relationship between ...