AboutPhilip Carlson Ph.D. (Cand.) Expertise Prefer questions regarding general chemistry, analytical chemistry, and physical chemistry. Have less knowledge about organic chemistry but can help with most undergraduate organic chemistry questions not related to reactions and their mechanisms.
Experience Highly experienced in physical chemistry both theoretical and experimental. Current research focus is fluorescence spectroscopy and electronic structure theory (e.g. quantum mechanics). Past research focus was in analytical chemistry in the area of photocatalysis.
Organizations American Chemical Society;
Society of Christian Philosophers;
Evangelical Philosophical Society
Publications Lori A. Pretzer, Philp J. Carlson, and Joel E. Boyd. "The effect of Pt oxidation state and concentration on the photocatalytic removal of aqueous ammonia with Pt-modified titania." J. Photochem. Photobiol. A: Chemistry. 200 (2008) 246-253. ;
Philip J. Carlson, Lori A. Pretzer, and Joel E. Boyd. "Solvent Deposition of titanium dioxide on acrylic for photocatalytic application." Ind. Eng. Chem. Res. 46 (2007) 7970-7976.
Education/Credentials A.S. in Chemistry from Garden City Community College, Garden City, KS;
B.S. in Mathematics from Wayland Baptist University, Plainview, TX;
B.S. in Chemistry from Wayland Baptist University, Plainview, TX;
Ph.D. (Cand.) in Physical Chemistry at Iowa State University, Ames, IA;
B.A. in Evangelism and Missions;
M.A. in Theological studies (In progress) from Louisiana Baptist University
Question Hello!
I am doing an experiment on enthalpy change of neutralization. Why is strong acid/strong base reaction is faster than a weak acid/strong base reaction? (The weak acid/strong base reaction took a onger time to reach its hishest temperature)
Thanks a lot for your help.
Answer There are a number of factors to consider in this type of situation. First, I will assume that the temperature was the same, that the strong base was the same in each situation, that there was no buffer involved, that the solvent (as well as the acid choice and base choice) allows for no common ion effects or other equilibrium effects. All things being equal and the only change is the acid then we can assume the following.
How can we define a weak acid? This is generally done according to the pKa value. The pKa value can give us a lot of information about an acid. If the acid is a strong acid we are saying that it can deprotnate quickly and completely. A weak acid will have more difficulty deprotnating. In your neutralization reaction the strong acid/strong base would probably both be responding quickly and deprotnating/protnating quickly. This will allow the appropriate species to be present and to react together. Hence, the neutralization reaction would happen faster.
In the weak acid/strong base case we see the weak acid deprotnating at a slower rate. Since the base can only neutralize the acid it has to "wait" to react until enough protons are available from the weak acid. So, picture it like this:
The weak acid begins to deprotnate and establish an equilibrium between protnated and deprotnated. When the eq is established it will not release any more acidic protons. However, we also have strong base that is "gobbling" up all the protons the acid is releasing. As the base eats up the available protons he eq established before is disturbed and so it has to release more protons from the weak acid to get back to its desired eq. At which time the base steals the protons again. This back and forth waiting game is responsible for the longer time that you observed.
