Saturday, 26 September 2015

inorganic chemistry - Reaction of borax with NaOH


How does borax react with NaOH? My textbook says that sodium peroxoborate is formed. I couldn't find the reaction anywhere else. Can anyone verify as well as explain it?



Answer



The following reaction schemes are adapted from [1, pp. 76–77]. Amorphous borax $\ce{Na2B4O7}$ forms tetrahydroxoborate in concentrated sodium hydroxide solution:


$$\ce{Na2B4O7 + 7 H2O + 2 NaOH → 4 Na[B(OH)4]}$$


Upon fusion sodium metaborate is formed:


$$\ce{Na2B4O7 + 2 NaOH →[\pu{700-750 °C}] 4 NaBO2 + H2O}$$


In order to form peroxoborate, a peroxide should be introduced in the first place, e.g. by using hydrogen peroxide (see also Preparation of Sodium Peroxoborate):


$$\ce{Na2B4O7 + 2 NaOH + 4 H2O2 + 11 H2O → 2 Na2[B2(O2)2(OH)4] * 6H2O}$$



References



  1. R. A. Lidin, V. A. Molochko, and L. L. Andreeva, Reactivity of Inorganic Substances, 3rd ed.; Khimia: Moscow, 2000. (in Russian)


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