Question

Borax is prepared by treating colemanite with:
A.) ${NaNO_3}$
B.) $NaCl$
C.) ${Na_2CO_3}$
D.) $NaHCO_3$

Answer 1

Borax is a naturally occurring mineral with a powdery white appearance. It is also called sodium borate, sodium tetraborate, or disodium tetraborate. It is one of the most important boron compounds having chemical formula $[{Na_2B_4O_7}\cdot10{H_2O}]$. It is found in hydrated form.

Complete answer:
Let us see the chemical reaction between Colemanite (${Ca_2B_6O_{11}}$) and Sodium carbonate (${Na_2}C{O_3}$).

$Ca_2B_6O_{11} + 2Na_2CO_3 \xrightarrow{\text{heat}} 2 CaCO_3 + Na_2B_4O_7 + 2NaBO_2$

Here we can see that when colemanite (${Ca_2B_6O_{11}}$) reacts with sodium carbonate (${Na_2CO_3}$) in the presence of heat to form the borax (${Na_2B_4O_7}$) along with calcium carbonate and sodium metaborate. Sodium metaborate is the byproduct of this reaction which is useful in the preparation of borosilicate glasses. It is also used as a component of herbicides and antifreeze products.
Hence, we can say that borax (${Na_2B_4O_7}$) is prepared by treating colemanite (${Ca_2B_6O_{11}}$) with sodium carbonate (${Na_2CO_3}$).

So the correct option is C).

Note: In this one should remember we won’t get borax directly we have to cool the concentrate filtrate to get the crystal of borax and while solving this type of question we must remember all the reactant and product sometime the question may asked about the product formed .