Obtaining calcium iodide from calcium and iodine According to:

https://www.webelements.com/calcium/chemistry.html

Calcium reacts with iodine upon heating as follows:

$\text{Ca}_{\,(s)} + \text{I}_{2\,(g)} \to \text{CaI}_{2\,(s)}$

I am effectively attempting this by dropping elemental calcium and iodine into a flask and putting it under a Bunsen burner. I have a tube leading from the flask to a beaker of water to safely condense escaping iodine gas.

However, this reaction is not occurring at any appreciable rate. I am wondering if I should be using powdered calcium instead of these larger pebble-sized chunks or if a Bunsen burner is insufficient to breach the energy barrier. Are these measures or others sufficient to increase the rate of reaction?
Looks like the Bunsen burner is not providing enough energy for the reaction to occur. AFAIK, you need around 200-400°C of heat for the reaction to occur. Yes, you can always powder the calcium metal to increase surface area and see if the reaction is occurring or adopt simple(chemical) methods. You can react any calcium salt with hydroiodic acid to form calium iodide. I am using calcium carbonate as example[1]:

$$\ce{CaCO3 + 2 HI → CaI2 + H2O + CO2}$$

Or alternatively make a iodide of iron and make it react with a calcium salt[2]. There are many more ways to make calcium iodide in [2]. You can look at them but these two methods is by far the most simple methods.

References:


https://en.wikipedia.org/wiki/Calcium_iodide
Caty J. Braford;  H. A. Langenhan; A preliminary report on the composition of syrup of calcium iodide N. F. V. DOI:https://onlinelibrary.wiley.com/doi/pdf/10.1002/jps.3080180218
http://albumen.conservation-us.org/library/monographs/sunbeam/chap10.html