An Endothermic Reaction Submitted by: Norman E. Burt, Hebron Academy, Hebron, Maine04238 Checked by: E. C. Kostansek, Hiram College, Hiram, Ohio 44234 PREPARATION
Approximately 38 g of ammonium thiocyanate, NH4SCN, and 79 g of hydrated barium hydroxide, B a ( 0 H ) ~ HzO, 4 will be required as well as a 500-ml Florence flask.
the outside of the flask becoming frosted with condensed water vapor and quite cold to the touch. The odor of ammonia gas can be detected as one of the products of the reaction.
DEMONSTRATION
REMARKS
Place the ammonium thiocyanate and barium hydroxide in the flask and swirl the contents. The reaction is slow to begin, requiring several seconds for the solid reactants to mix. When the reaction begins the mixture will start to produce a liquid solution and within several minutes all solid reactants will have dissolved. As the reaction proceeds the mixture will cool down to about -1O0C,with
The essential reaction occuring is the barium hydroxide reacting with the ammonium thiocyanate to produce ammonia, barium thiocyanate, and water.1
A178
/ Journal of Chemical Education
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Ba(0H)a + ~ N H I S C N Ba(SCN)a + 2NH.
'
+ 2H20
Andrieth, L. F.,(Editor-in-Chian, "Inorganic Synthesn,"MeCraw~HillBmkCompany, Inc., New York. Vol.ll1.p 24. Submitted by K a d M Hemtein.
