Wednesday, January 24, 2018

everyday chemistry - Physical state of the carbon denoted with "gr"



I would like to know what does a gr mean when used to represent the physical state of the carbon, for example, in the synthesis of the glucose


$$\ce{6C_{(gr)} + 6H2_{(g)} + 3O2_{(g)}-> C6H12O6_{(\ell)}} \quad,$$


what does the $\mathrm{gr}$ mean?



Answer



The letters in brackets indicate state of aggregation (includes state of matter, crystal structure (solids) and atomicity (gases)), therefore $\ce{C_{(gr)}}$ most likely refers to graphite. Often one can also see $\ce{C(s, gr)}$ or $\ce{C(s, graphite)}$ There is a nice demonstration in [1, p. 248]:



$$\ce{C(gr) + O2(g) <=> CO2(g)}$$ Here $\ce{(g)}$ indicates that the compound is gas, [...], and $\ce{(gr)}$ that carbon is graphite (not many people will burn diamonds, even if they are chemists).



P. S. According to IUPAC recommendations, subscript notation is deprecated.




  1. Metiu, H. Physical Chemistry: Thermodynamics; Garland Science, 2006. ISBN 978-1-315-31491-4.


No comments:

Post a Comment

digital communications - Understanding the Matched Filter

I have a question about matched filtering. Does the matched filter maximise the SNR at the moment of decision only? As far as I understand, ...